Browsing by Person "Rodehutscord, Markus"

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The active core microbiota of two high-yielding laying hen breeds fed with different levels of calcium and phosphorus
(2022) Roth, Christoph; Sims, Tanja; Rodehutscord, Markus; Seifert, Jana; Camarinha-Silva, Amélia
The nutrient availability and supplementation of dietary phosphorus (P) and calcium (Ca) in avian feed, especially in laying hens, plays a vital role in phytase degradation and mineral utilization during the laying phase. The required concentration of P and Ca peaks during the laying phase, and the direct interaction between Ca and P concentration shrinks the availability of both supplements in the feed. Our goal was to characterize the active microbiota of the entire gastrointestinal tract (GIT) (crop, gizzard, duodenum, ileum, caeca), including digesta- and mucosa-associated communities of two contrasting high-yielding breeds of laying hens (Lohmann Brown Classic, LB; Lohmann LSL-Classic, LSL) under different P and Ca supplementation levels. Statistical significances were observed for breed, GIT section, Ca, and the interaction of GIT section x breed, P x Ca, Ca x breed and P x Ca x breed (p < 0.05). A core microbiota of five species was detected in more than 97% of all samples. They were represented by an uncl. Lactobacillus (average relative abundance (av. abu.) 12.1%), Lactobacillus helveticus (av. abu. 10.8%), Megamonas funiformis (av. abu. 6.8%), Ligilactobacillus salivarius (av. abu. 4.5%), and an uncl. Fusicatenibacter (av. abu. 1.1%). Our findings indicated that Ca and P supplementation levels 20% below the recommendation have a minor effect on the microbiota compared to the strong impact of the bird’s genetic background. Moreover, a core active microbiota across the GIT of two high-yielding laying hen breeds was revealed for the first time.
Approaches to increase digestibility of Bangladesh ruminant feed resources in order to mitigate enteric methane production
(2024) Bashar, Muhammad Khairul; Rodehutscord, Markus
Multiple analyses have shown that the rising human population, urbanization, and consumer preferences affect the demand for livestock products in developing countries. Concurrently, human population and urbanisation growth are reducing the likelihood of newly cultivated land producing feeds or restoring damaged pastures. Using low-quality roughage more efficiently is an option, but such roughages have drawbacks, including high structural carbohydrate and low nitrogen contents, which lead to poor palatability and nutrient utilisation including emission of methane (CH4) that is harmful to the environment and a loss of energy to the animal. Using commonly accessible legumes and tree foliage could be a possibility to address the need for N and CH4 mitigation due to their high crude protein and secondary compound contents. In order to evaluate the potential of specific combinations of roughages, concentrates, and other feeds, it is necessary to determine the feeding values, in vitro ruminal fermentation, and CH4 production of single feeds, as well as the promising interaction (associative) effects between single feeds when combinded in a ration. This may allow for formulating a better balanced total mixed ration (TMR) for ruminants, which was the main goal of the present doctoral study. Eighteen feedstuffs from Bangladesh were chosen, including roughages such as crop residues (rice straw, urea molasses treated straw and maize stover), silages (Napier silage and Maize silage), common grasses (German grass, Para grass and Napier grass) and leguminous fodder (Ipil-ipil, Glicidia, Alfalfa hay and Moringa tops) and concentrates (crushed wheat, crushed maize, Wheat bran, Kashari bran, and Rice bran). In Study 1, the single feeds were characterized by comprehensive chemical analysis and in vitro production of total gas and methane using the Hohenheim gas test. Based on the results of Study 1, rice straw, German grass, Napier silage, and maize silage were used in Study 2 and incubated in vitro alone or after substitution by Ipil-ipil and Gliricidia at levels of 10%, 20%, 30%, and 40%, respectively. In Study 3, mixtures of roughages and leguminous fodder (rice straw + 40% Ipil-ipil, German grass + 10% Ipil-ipil, Napier silage + 30% Ipil ipil, and maize silage + 30% Ipil-ipil) were combined with single concentrates in order to identify the most promising mixtures in regard to digestibility and methane production. Eventually, 24 TMR were formulated using six for each type of roughage in Study 4. These TMR were comprised of 60% of the same combination of roughage as used in Study 3 and 40% of various combinations of concentrates including TMR-1 (60% rice bran + 10% wheat bran + 30% kashari bran), TMR-2 (30% rice bran + 10% wheat bran + 60% kashari bran), TMR-3 (10% rice bran + 60% wheat bran + 30% kashari bran), TMR-4 (10% rice bran + 30% wheat bran + 60% kashari bran), TMR-5 (60% rice bran + 30% wheat bran + 10 kashari bran), and TMR-6 (30% rice bran + 60% wheat bran + 10% kashari bran) in order to identify suitable TMR for maximising ruminal fermentation and reducing the CH4 production in vitro. In all studies, the total gas production (GP), digestibility of organic matter (dOM), metabolisable energy (ME), and net energy for lactation (NEL) were determined after incubating 200 mg of feed with a rumen fluid-buffer solution for 72 hours. In addition, the CH4 concentration in the produced gas was measured after incubating 120 mg of feed for 24 hours. Measured values of the mixed feed were compared to estimated values, where the estimated values were weighted means of the values of the individual feeds, to determine the associative effects between the feed ingredients (Study 2 and Study 4). In Study 1, the concentration of acid detergent fibre (ADF), neutral detergent fibre (NDF), and acid detergent lignin (ADL) was the lowest in leguminous fodder while the crude protein (CP) concentration was the hightest, followed by the common grasses and the silages. The crop residues showed the lowest CP and the highest cell wall fraction concentrations. The dOM, ME, and NEL of crushed wheat and crushed maize were significantly higher (p<0.05) than those of other feedstuffs. The same differences were found (p<0.05) for CH4 concentration (% of GP) and CH4 production (L CH4/kg dOM). The dOM and ME of German grass and Ipil-ipil were higher (p<0.05), whereas the CH4 concentration and CH4 production were lower compared to that of crop residues and other common grasses. The CH4 production of single feeds decreased with increasing concentrations of CP, ADF, and ADL, whereas it increased with NDF concentration. These findings enabled development of more balanced diets for ruminants with the aim of improved digestibility and reduced CH4 emission while making use of widely available feed resources in Bangladesh. Study 2 aimed to evaluate the in vitro ruminal fermentation, CH4 production, and associative effects between low-quality roughages and CP supplements. The gas production after 24 hours (GP24) and rumen fermentation rate increased (p<0.05) with increasing addition of Ipil-ipil to rice straw. It also resulted in a gradual increase of dOM and ME (p<0.05) of the mixture, reaching maximum values (59.1% and 7.60 MJ ME/kg DM) and maximum reductions in CH4 concentration and CH4/dOM (6.9% and 11.7%) compared to the control with Ipil-ipil addition at 40% of DM. When Ipil-ipil was added at 30% to Napier silage, the same trend was observed for dOM and ME (56.5%, and 7.55 MJ ME/kg DM) and CH4 concentration and CH4/dOM (5.3% and 13.3%). Ipil-ipil did not significantly interact with high quality roughages such as German grass and maize silage. Increasing the addition of Gliricidia to the roughages in Study 2 led to a decrease in GP24, dOM, ME, and CH4 production. The highest levels of the associative effects (p<0.05) were seen when 40% Ipil-ipil was added to rice straw and 30% was added to Napier silage. In conclusion, adding Ipil-ipil to low-quality roughages is superior to Gliricidia and showed promising results, with the ranking as follows: rice straw + 40% Ipil-ipil > Napier silage + 30% Ipil-ipil > maize silage + 30% Ipil-ipil > German gras + 10% Ipil-ipil. Study 3 and Study 4 had the overarching purpose to determine which combination of single concentrates and combinations of concentrates with roughage produced the best mixed feed in terms of rumen fermentation, CH4 reduction potential, and associative effect. The CP and non-stach carbohydrate contents of the Ipil-ipil-based mixed feed was enhanced by adding Wheat bran and Kashari bran as single concentrates, which had a favourable effect on rumen fermentation and gas production but had the opposite effect on CH4 production when compared to the addition of Rice bran. In Study 4, TMR were formulated using roughages and Ipil-ipil and addition of Wheat bran, Kashari bran, and Rice bran in various combinations. The TMR based on German grass and maize silage with specific bran combinations showed significant reductions in in vitro CH4 production, CH4 concentration, and CH4/dOM while maximising GP, dOM, ME, and the associative effects. To conclude, the results of chemical analyses and in vitro fermentation studies showed that specific combinations of roughages, protein feeds, and by-products available in Bangladesh have the potential to formulate rations for cattle that help making livestock production more sustainable. The results may be also relevant for other developing nations. It is suggested to verify the results of the present project by animal trials at local conditions.
Bi-objective optimization of nutrient intake and performance of broiler chickens using Gaussian process regression and genetic algorithm
(2023) Ahmadi, Hamed; Rodehutscord, Markus; Siegert, Wolfgang
This study investigated whether quantifying the trade-off between the maxima of two response traits increases the accuracy of diet formulation. To achieve this, average daily weight gain (ADG) and gain:feed ratio (G:F) responses of 7–21-day-old broiler chickens to the dietary supply of three nutrients (intake of digestible glycine equivalents, digestible threonine, and total choline) were modeled using a newly developed hybrid machine learning-based method of Gaussian process regression and genetic algorithm. The dataset comprised 90 data lines. Model-fit-criteria indicated a high model adjustment and no prediction bias of the models. The bi-objective optimization scenarios through Pareto front revealed the trade-off between maximized ADG and maximized G:F and provided information on the needed input of the three nutrients that interact with each other to achieve the trade-off scenarios. The trade-off scenarios followed a nonlinear pattern. This indicated that choosing target values intermediate to maximized ADG and G:F after single-objective optimization is less accurate than feed formulation after quantifying the trade-off. In conclusion, knowledge of the trade-off between maximized ADG and maximized G:F and the needed nutrient inputs will help feed formulators to optimize their feed with a more holistic approach.
Bone ash data in the context of phosphorus and phytase evaluation in poultry
(2021) Künzel, Susanne; Rodehutscord, Markus
Phosphorus (P) is an essential element that is crucial for various metabolic processes in the body of animals and humans. To keep the animals healthy and to obtain food products rich in nutrients, an adequate P supply is indispensable. Plant feedstuffs, the main components of poultry diets, contain P in a form that is only partially available to poultry. For this reason, poultry diets are often supplemented with mineral P. However, global rock phosphate reserves, where mineral P is mined from, are limited. Additionally, excessive P supply should also be avoided because of the environmental impact of P accumulation in the soil. Consequently, P supply not exceeding the requirements of poultry is essential to ensure animal wellbeing and to protect the environment. In order to feed diets with adequate concentrations of P, it is necessary to have suitable approaches for the determination of available P in the animal. The availability of P varies widely between feed components and it is also influenced by feed supplements and other factors. Bone ash analysis is an often-used tool to evaluate the relative bioavailability of P since a high amount of P is stored in the bones. A standard assay for bone ash analyses has never been agreed on. Therefore, many different approaches are described in the literature with an unknown impact on the results of P bioavailability studies. The main objective of the present thesis was to examine the suitability of bone ash data for the evaluation of available P in poultry with emphasis on methodological aspects. Therefore, different studies with broiler chickens and Japanese quail were conducted. The experiments comprised various aspects related to P availability in poultry. The effect of feed supplements in the form of phytase products, myo-inositol and a coccidiostat were evaluated. Furthermore, quantitative genetic analyses were performed. All experiments had in common that tibiotarsus (tibia) or foot ash data or both were used for the examination of the relative bioavailability of P. Based on the data that accrued during the studies described in the four manuscripts of this thesis, comprehensive methodological analyses were performed. The tibia and foot were compared regarding their appropriateness as a trait for the evaluation of the relative bioavailability of P by using bone ash data. The relationship between the two traits was investigated, as well as the relationship between foot or tibia ash and quantitative P measurements. Additionally, P concentration in the ash of both bone fractions was analysed and compared. Results indicated only minor differences between tibia and foot ash data. No clear preference for one of them could be deduced from the data. The left and right feet of broiler chickens were compared in terms of both ash concentration and total ash amount. Significant differences between the two feet of the same animal were detected for both traits. Consequently, not only the choice of the bone fraction but also of the body side should be considered when sampling for bone ash data. Ash data are mostly expressed as a concentration of the dry matter content of the bone. Also possible is the use of the absolute ash amount. The relationship of both ways of expression with traits of quantitative P measurements was analysed by using correlation coefficients and regression analyses. Results showed that the absolute ash amount was at least as suitable as ash concentration but has the advantage that it is easier to determine. Possible selection procedures for animals for bone ash analyses were simulated with data from two of the experiments. Often it is not possible to use all animals involved in an experiment for bone ash analyses. Therefore, the influence of sampling frequency and selection method on the outcome of P availability studies was evaluated. Results indicated that the number and selection method of animals for bone ash data might influence the results. However, it was not possible to recommend a specific selection method based on the obtained results. Estimates of heritability and genetic correlations showed the suitability of bone ash data as a proxy trait for P efficiency breeding of poultry. The absolute amount of bone ash data appeared to be most promising for this purpose. Bone ash data are a very useful and easy to determine trait to estimate the relative bioavailability of P. However, investigations performed in this thesis showed the importance of a careful selection of methods. A standardised assay would be helpful to obtain meaningful and more comparable estimates of relative P bioavailability.
Degradation of crude protein and starch of corn and wheat grains in the rumen
(2016) Seifried, Natascha; Rodehutscord, Markus
The major objectives of the present thesis were to characterize the ruminal crude protein (CP) and starch degradation of different genotypes of corn and wheat grains and to predict the effective degradation (ED) of CP and starch with easily measurable characteristics. The in situ method is the standard technique to study the ruminal degradation of feeds in many feed evaluation systems. This technique was originally applied to study forages and it was therefore necessary to clarify methodical details related to the measurements of in situ starch degradation from cereal grains. Two in vitro and one in situ approach were conducted to study the loss of secondary starch particles from bags with different pore sizes used for the in situ incubation of different cereal grains. In the first in vitro study ground wheat was incubated in bags (pore size: 50 µm) over different time spans in a modified rumen simulation technique. Bag residues and fermenter fluids were analyzed for their starch content. In the second in vitro study ground wheat, barley, and corn were incubated with bags of pore sizes of 50, 30 (except corn), 20, and 6 µm. In the in situ study ground wheat, barley, corn, and oats were rumen incubated over different time spans using bags with pore sizes of 50, 20, and 6 µm. The starch content of the grains and bag residues was analyzed enzymatically and the degradation characteristics of starch were calculated for each grain type and pore size. It was shown for the first time that incubating wheat and barley in bags with 50 and 30 µm pore size lead to a substantial amount of secondary starch particle losses during incubation process in vitro. These losses were not detectable when the grains were incubated with bags having pore sizes of 20 and 6 µm. Independent of the bags’ pore size no secondary starch particle losses were found by the incubation of corn. Thus corn can be studied in situ even with bags with 50 µm pore size. Oats showed very high washout losses with all pore sizes tested in the present thesis and therefore none of them is suitable to study the starch degradation measurements of oats. Because of methodical problems of gas accumulation in bags having pore sizes < 50 µm, no recommendations can be provided for the in situ evaluation of wheat and barley. Further research is necessary to solve these problems. In the second and third study of the present thesis ruminal in situ degradation of 20 corn grain genotypes and 20 wheat grain genotypes was measured in three lactating Jersey cows. In both experiments the same techniques were used to characterize the ruminal degradation of CP and starch. Ground grains (2 mm) were rumen incubated in bags (50 µm pore size) over different time spans. Grains and bag residues were analyzed for their CP and starch content. The degradation parameters and the ED were calculated for dry matter (DM), CP, and starch. Gas production (GP) of ground grains (1 mm) was recorded after incubation over different time spans in buffered ruminal fluid and fitted to an exponential equation to determine GP parameters. To predict ED of CP and starch correlations with physical and chemical characteristics and in vitro measurements were evaluated and stepwise multiple linear regression analyses were applied. The in situ parameters (soluble fraction, potential degradable fraction, and degradation rate) varied widely between genotypes of corn and wheat grains. The ED of DM, CP, and starch showed a high variation for corn grain genotypes. Due to the high degradation rates, the ED of wheat grains were similar between genotypes. The GP rate was in good agreement with the in situ values for corn grains, whereas no systematic relationship between both methods was observed for wheat grains. Evaluation of correlation analysis showed significant relationships between calculated ED of CP and several amino acids (AA) for both grain types. This indicates that the protein composition of the grains influences CP degradation in the rumen. Similar relationships were found between the same AA and ED of starch of corn grains which highlights the impact of the protein composition on ruminal starch degradation for this grain type. For both grain types, the ED of starch and CP could be predicted accurately from physical and chemical characteristics alone or in combination with GP measurements. Thus, the equations presented in the present thesis can be used to obtain rapid and cost effective information on ruminal degradation of CP and starch for corn and wheat grains. The results of the present thesis show that there is considerable variation of ruminal CP and starch degradation from different genotypes of corn and also – albeit to a lesser extent – for wheat grains. Differences in ED of starch should be taken into account when formulating rations containing significant amounts of corn and wheat grains. In the case of corn grains differences in ED of CP should also be accounted for.
Dietary phosphorus and calcium in feed affects miRNA profiles and their mRNA targets in jejunum of two strains of laying hens
(2021) Iqbal, Muhammad Arsalan; Ali, Asghar; Hadlich, Frieder; Oster, Michael; Reyer, Henry; Trakooljul, Nares; Sommerfeld, Vera; Rodehutscord, Markus; Wimmers, Klaus; Ponsuksili, Siriluck
Phosphorus (P) and calcium (Ca) are critical for egg production in laying hens. Most of P in plant-based poultry diet is bound as phytic acid and needs to be hydrolysed before absorption. To increase P bioavailability, exogenous phytases or bioavailable rock phosphate is added in feed. There is growing evidence of the importance of miRNAs as the epicentre of intestinal homeostasis and functional properties. Therefore, we demonstrated the expression of miRNA profiles and the corresponding target genes due to the different levels of P (recommended vs. 20% reduction) and/or Ca (recommended vs. 15% reduction) in feed. Jejunal miRNA profiles of Lohmann Selected Leghorn (LSL) and Lohmann Brown (LB) laying hens strains were used (n = 80). A total of 34 and 76 miRNAs were differentially expressed (DE) in the different diet groups within LSL and LB strains respectively. In LSL, the DE miRNAs and their targets were involved in calcium signaling pathway, inositol phosphate metabolism, and mitochondrial dysfunction. Similarly, in LB miRNAs targets were enriched in metabolic pathways such as glutathione metabolism, phosphonate metabolism and vitamin B6 metabolism. Our results suggest that both strains employ different intrinsic strategies to cope with modulated P and Ca supply and maintain mineral homeostasis.
Effects of a reduction of dietary levels of calcium and phosphorus on performance, bone minerals and mineral excretion of turkey breeder hens in the rearing and laying period
(2023) Gickel, Julia Maria; Rodehutscord, Markus
Phosphorus (P) is an essential mineral in feed for livestock and has finite resources all over the world. The aim of this study was to obtain an idea about the reduction potential of P in the diets of turkey breeders. As the metabolism of P is interlinked with the metabolism of calcium (Ca), Ca was also examined. Therefore, the requirements of P and Ca were studied using a factorial approach. As data about the requirements of these minerals in turkey breeders is limited, the present study mostly used data from other poultry species. Thus, this study can be viewed as an approach to building new resilient data for turkey breeder hens. The results of the factorial approach were embedded in a feeding program for turkey breeder hens during rearing and laying with two different treatments. One group was fed a standard feed (practical diet used before the trial), while the other group was fed a Ca/P reduced feed. In total, four trials were conducted: trials I and III focused on the rearing period while trials II and IV focused on the laying period. All trials were observed independently but the hens from trial I were used also in trial II afterwards for studying long-term effects. In each trial, body weight and feed intake were measured throughout the trial period. Bone mineralization was studied in trial I, including analyses of bone ash as well as Ca and P in the bone ash from the tibia of fallen and culled animals. The egg components were studied in eggs from trial II, including analyses of the percentages of albumen, egg yolk, and egg shell; Ca in albumen; P in albumen; Ca in egg yolk; P in egg yolk; water in egg shell; Ca in egg shell; and P in egg shell. In trials II and IV, laying performance, egg weights, number (and causes) of culled eggs, fertility, hatchability, as well as body weight and fitness of the hatchlings were additionally observed. At the end of each trial, the concentrations of dry matter, Ca, and P in manure were analyzed and a nutrient balance was calculated to classify the results. Body weight development exhibited significant differences between the treatments in eight out of 30 weeks in trial I (five weeks had a higher mean weight in the group with standard feed; three weeks had a higher mean weight in the group with Ca/P reduced feed); three out of 28 weeks in trial II (two weeks had a higher mean weight in group with Ca/P reduced feed; one week had a higher mean weight in the group with standard feed); four out of 30 weeks in trial III (higher mean weight in the group with Ca/P reduced feed); and two weeks out of 28 in trial IV (higher mean weight in the group with Ca/P reduced feed). The feed intake data also fluctuated, with three out of 30 weeks exhibiting a significant difference in trial I (higher mean feed intake in the group with Ca/P reduced feed) and one week with a significant difference in trial II (higher mean feed intake in the group with standard feed). The observations throughout all of the trials revealed the tendency for a higher mean feed intake in the groups with Ca/P reduced feed. A significant difference concerning bone mineralization was not observed. Moreover, the results of laying performance, fertility, and hatchability exhibited no differences between the treatments. Regarding the egg weight in trial II, there were eight weeks with a significant difference between the treatments (seven weeks with a higher mean egg weight in the group with standard feed; one week with a higher mean egg weight in the group with Ca/P reduced feed). In trial IV, only one week exhibited a significant difference between the treatments (higher mean egg weight in the group with Ca/P reduced feed). Regarding the weight of hatchlings in trial II, three weeks had a significant difference between the groups (higher mean weight in the group with standard feed). In trial IV, no significant difference was observed for any week all throughout the trial period. The analyses of egg components revealed significant differences between the treatments according to the percentages of albumen and egg yolk and the calculated value of total Ca in the egg (including the shell). In trials I and III, significant differences existed between the treatments in the concentration of Ca in manure, with a lower level in the group with Ca/P reduced feed. This study concluded that a reduction in the dietary levels of Ca from 1.00–1.10% to 0.56–0.80% and of P from 0.48–0.61% to 0.35–0.50% (av. P) or 0.70–0.80% to 0.50–0.60% (total P) in rearing and a reduction of the dietary levels of Ca from 2.90% to 2.80% or 2.60% and of P from 0.36% to 0.30% or 0.24% (av. P) or from 0.65% to 0.50% (total P) in laying in the feed of turkey breeder hens are possible and did not result in disadvantages. As the present study also compared the results with required recommendations and target levels from breeding companies, it was also able to conclude that these levels are obsolete and should be adjusted downwards.
Effects of monensin and tannin extract supplementation on methane production and other criteria of rumen fermentation in vitro and in long-term studies with sheep
(2013) Wischer, Gerald; Rodehutscord, Markus
Ruminants increasingly attract public concern due to their methane release and contribution to the greenhouse effect. One strategy to reduce the release of methane is to modify microbial fermentation in the rumen by the use of feed additives such as monensin and tannin extracts. However, other characteristics of fermentation including the synthesis of microbial protein may also be affected. The aim of the present studies was to provide a comprehensive evaluation of the effects of monensin and tannin extracts on ruminal fermentation and methane production. The ionophore monensin is known to increase feed efficiency in ruminants. Although the use of silages is common practice in cattle feeding, the effects of monensin on the fermentation of silages in the rumen and microbial protein synthesis are lacking. Monensin has often been described to have indirect effects on methane production resulting from its effects on feed intake, protozoa and Gram-positive bacteria. It has rarely been studied whether monensin can reduce methane production without adverse effects on other criteria of rumen fermentation. The first objective therefore was to investigate the effects of different dosages of monensin on methane production and microbial protein synthesis when supplemented to different silages in two in vitro systems (Study 1). In Experiment 1 of Study 1, 15 g of oven-dried grass silage alone or combined with a concentrate was incubated in a rumen simulation (Rusitec) over a period of 13 d to examine the effects of monensin supplementation (2 or 4 mg/d, n = 4) on the production of total gas, methane, volatile fatty acids (VFA), degradation of nutrients and microbial protein synthesis. In Experiment 2 of Study 1, different dosages of monensin (0.5, 1, 2, 6 and 10 µg) were supplemented to syringes containing 120 mg of grass silage alone, grass silage combined with concentrates, or maize silage alone. After 24 h of incubation the effects of monensin on total gas, methane and VFA production were determined. In Experiment 1 monensin inclusion to grass silage and grass silage combined with concentrate resulted in a decreased total gas, methane and acetate production, while propionate production was increased. Along with a decreased degradation of crude protein, ammonia concentration in the system was reduced. While microbial protein originating from solid associated microbes decreased with monensin inclusion, microbial protein from liquid associated microbes was increased, resulting in an increase in total microbial protein synthesis. In Experiment 2, different dosages of monensin reduced methane production in grass silage (17%), grass silage combined with concentrate (10%) and maize silage (13%) without adverse effects on total gas production. Based on these two in vitro experiments it was concluded that monensin is able to reduce methane production without a major decrease in total gas and VFA production and degradation of organic matter. Although microbial fractions were differently affected, the total microbial protein synthesis was increased upon monensin supplementation. Tannins are secondary plant compounds that are known to complex with feed and microbial proteins. Several products from this heterogeneous group have shown potential to affect rumen fermentation in vivo and, even more, in vitro, but are often accompanied by negative effects on digestibility, feed intake and microbial protein synthesis. In Study 2 of the present work, ten tannin extracts (chestnut, mimosa, myrabolan, quebracho, sumach, tara, valonea, oak, cocoa and grape seed) and four monomers of rapeseed tannin (pelargonidin, catechin, cyanidin and sinapinic acid) were screened in grass silage based diets in successive runs using the Hohenheim Gas Test. The objective was to determine the optimal dosage of each tannin extract to cause a maximal methane reduction without negative effects on total gas production. Whereas the supplementation of pelargonidin and cyanidin to grass silage did not reduce methane production; catechin and sinapinic acid reduced methane production without affecting total gas production. Except tara extract, all tannin extracts reduced methane production by 8 to 28% without adverse effects on total gas production. Based on these results, chestnut, grape seed, myrabolan, sumach and valonea extract were investigated in a second step in a Rusitec to determine their effects on degradation of nutrients, VFA and ammonia production, and particularly on microbial protein synthesis. All tannin extracts were supplemented at similar dosages of 1.5 g to 15 g of grass silage. The supplementation of chestnut resulted in the greatest decrease in methane production (63%), followed by valonea (35%), grape seed (23%), sumach (18%), and myrabolan (7%; not significantly different from the control). While chestnut extract reduced acetate production by 19%, supplementation with grape seed or myrabolan extract increased acetate production; however, degradation of fibre fractions was reduced in all tannin treatments. Degradation of dry and organic matter was reduced by all tannin extracts, but there were no differences between tannin treatments. Crude protein degradation and ammonia production were also reduced by tannin extract supplementation. Microbial protein synthesis and its efficiency were not affected by tannin supplementation, which indicates that a reduction in methane production due to tannin extract supplementation is possible without negatively affecting microbial protein synthesis. Chestnut and valonea extract had the greatest potential in reducing methane production without negative effects on rumen fermentation of grass silage and microbial protein synthesis. Therefore, these tannin extracts were investigated for their long-term effects in sheep (Study 3). In Experiment 1 of Study 3, sheep receiving the control, chestnut or valonea treatment (each n = 4) were fed 842 g/d of hay (fresh weight). The animals on the control treatment also received 464 g/d of concentrate, and animals on the tannin treatments received the same amount of concentrate but were also fed 20 g of the respective tannin extract. Following initiation of tannin feeding, methane release from sheep was measured in 23.5 h intervals in respiration chambers on day 1, 8, 15, 29, 57, 85, 113, 148, and 190. In three balances periods faeces and urine were collected for 6 and 3 days, respectively. Effects on nutrient digestibility, nitrogen and energy metabolism were evaluated, with microbial protein synthesis estimated from the urinary excretion of purine derivatives. Based on the results of Experiment 1, a second experiment was conducted four month after the start of Experiment 1. Experiment 2 had the same study design and data collected, but the dosage of tannin extracts was doubled compared to Experiment 1 (0.9 vs. 1.7 g tannin extract/kg body weight) and the duration was shorter (85 days). Hay and concentrates used in both experiments were also evaluated using the Hohenheim Gas for their effects on total gas and methane production. In both experiments, methane release was not significantly reduced by tannin extract supplementation when analysed over the whole experimental period. In Experiment 1 the supplementation of chestnut extract on day 190 resulted in a reduced methane release. In both experiments, on day 1 a numeric reduction in methane release for the tannin treatments was observed, with a greater reduction recorded for the higher dosage used in Experiment 2. This trend disappeared by day 57. In the third balance period of Experiment 1, digestibility of dry and organic matter was reduced by tannin supplementation. The digestibility of crude protein was reduced in both experiments, whereas the digestibility of fibre fractions was not influenced. In both experiments a long-lasting shift in nitrogen excretion from urine to faeces was observed, which occurred to a greater extent in Experiment 2. The urinary excretion of purine derivatives was not significantly affected by tannin supplementation, indicating that the microbial protein synthesis was not altered in either experiment. The in vitro methane production was reduced for concentrates containing tannin extracts, but it was not significantly affected when concentrates were incubated with hay. It is concluded that monensin added to different silages caused a decrease in methane production without affecting total gas production but with an increased microbial protein synthesis. Nine of the ten considered tannin extracts and two tannin monomers decreased methane production without affecting total gas production. The Rusitec study confirmed the great potential of chestnut and valonea extract to reduce methane production without negative effects on microbial protein synthesis. However, neither chestnut nor valonea extract reduced the methane release in sheep when fed over a longer period of time. It is assumed, that rumen microbes adapted to the tannin dosages in terms of methane release but not nitrogen metabolism, as there were long-lasting effects on nitrogen excretion. The shift in nitrogen excretion can have a positive effect on the environment due to the reduced potential of ammonia emission from the urine. Both in vitro systems used in the present studies showed effects of tannin extracts that were considerably different from those observed in sheep. The monomers investigated in the present study are the basic units of condensed tannins, whereas the tannin extracts selected in vitro only contain hydrolysable tannins. It is possible that monomers of chestnut and valonea extract may reduce methane production, whereas higher dosages of these tannin extracts cause negative effects on feed intake, digestibility and microbial protein synthesis. Further investigations should focus systematically on the transfer of in vitro studies to estimate in vivo responses. Therefore, a parallel implementation of different in vitro and respiration studies would be of great value.
Entwicklung und ernährungsphysiologische Bewertung mikrobieller Hybrid-Phytasen
(2023) Metten, Alexander; Rodehutscord, Markus
To degrade the organic phosphate storage in the best possible way, it is necessary to increase phytase efficiency in vivo. Both a better understanding of the influencing factors limiting phytate degradation in vivo and a continuous improvement of the biochemical properties of phytases to be best adapted to the conditions in the digestive tract of non-ruminants will help to achieve this. Therefore, the main objective of this work was the generation of a large number of sequentially unique hybrid phytases by directed recombination of known phytase genes with the goal to achieve improved biochemical properties compared to the wild-type phytases used. The focus of this work was the biochemical and nutritional evaluation of the newly generated hybrid phytases with respect to their suitability as feed supplements. All hybrid phytases examined showed more efficient InsP6 degradation at pH 3.0 than at pH 5.5, although the phytase activity supplemented was the same at both pH values. While InsP6 was dephosphorylated to InsP1-2 in many cases at pH 3.0, accumulation of the Ins(1,2,5,6)P4 isomer occurred at pH 5.5. In an in vitro model simulating the digestive tract of broilers, hybrid phytases with high sequential homology to the E. coli and C. braakii phytase showed high accumulation of InsP4 isomers. Interestingly, these phytases preferentially formed the Ins(1,2,5,6)P4 isomer. In contrast, other hybrid phytases were able to degrade all InsP4 isomers and in some cases high InsP2 concentrations were observed. Another in vitro experiment with a complex feed matrix consisting of soybean meal, rapeseed meal, and wheat with a high mineral content, illustrated the negative influence of certain feed-related factors on phytase efficiency. InsP6 present in the feed was significantly less degraded by all phytases used compared to a corn and soy-based feed matrix with a low mineral content. While a hybrid phytase was able to completely dephosphorylate the InsP6 of the corn and soy-based feed matrix down to the InsP3 isomer resulting in high InsP2 concentrations, the InsP6 were still detectable in the in vitro model with the more complex feed matrix and high mineral content, despite identical reaction conditions. In a final feeding trial with broilers, one of the hybrid phytases was supplemented at two doses each (500 and 1500 FTU/kg) to evaluate its suitability as a feed supplement. Also, a commercial phytase was included in the study design at the same doses setting the benchmark for phytase efficiency. A low phosphorus experimental feed based on corn and soybean meal was used. The supplementation of the used hybrid phytase resulted in a dose-dependent increase in broiler performance data such as daily weight gain, feed intake and significantly improved feed efficiency compared to the basal ration without enzyme supplementation. In addition, foot ash content was increased by 21.6% at a dose of 1500 FTU/kg phytase, indicating significantly improved bone mineralization due to the released InsP6 phosphate. By analyzing InsP6 concentration and its degradation products in different segments of the digestive tract, efficient InsP6 degradation was observed. In contrast to the in vitro experiments, no accumulation of InsP3-4 isomers could be detected in crop, gizzard or small intestine. In addition to a high exogenous phytase activity, this result also suggests a high endogenous phytase as well as phosphatase activity in the digestive tract of broilers. It can be assumed that the absence of monocalcium phosphate in the experimental rations may have induced the expression of endogenous phytases and phosphatases. This assumption is confirmed by the high precaecal InsP6 degradation, which was 63.5% in the basal ration without phytase supplementation. Nevertheless, the used hybrid phytase significantly increased the precaecal InsP6 degradation to 76.3%. The high phytase efficiency was also reflected in the measured precaecal phosphorus digestibility, which was increased by 6.8% compared to the basal ration. The commercial phytase used showed comparable improvement in broiler performance data to the non optimized hybrid phytase. This project demonstrated the development of a variety of sequentially unique hybrid phytases by recombination of known phytase genes, which exceeded the biochemical properties of the wild-type phytases in some relevant aspects. Some of the phytases showed very efficient phytate degradation when simulating the digestive tract of broilers in vitro. Also, the suitability of the tested hybrid phytase as feed additives was demonstrated by the increased performance data of broilers. The higher performance data of the broilers could be attributed to efficient phytate degradation. To achieve maximum InsP6 degradation in vivo, the feed-related and animal-related factors on phytase efficiency need to be better understood.
Evaluation of the availability of different mineral phosphorus sources in broilers
(2012) Shastak, Yauheni; Rodehutscord, Markus
Inorganic feed phosphates are an indispensable supplement for compounding poultry feed. The requirement of available P in broiler chicks cannot be covered only with plant ingredients as P in plant feedstuff is largely presented in form of phytate which is only partially available in avian species. Due to the increase in prices for feed phosphates and environmental concerns associated with excessive excretion of P by livestock, the knowledge about the availability of P from mineral sources has gained in importance during the last decade. However, there is still no standardized method available for assessing the P availability of inorganic feed phosphates. Without knowledge of the exact quantitative values of the P availability for different P sources, it is not possible to formulate adequate diets without the risk of deficiency or excess supplementation. There are various approaches which are used by different laboratories for the determination of P availability. The main problem is, however, that it is not clear how the differences between approaches affect the results. The development of a standardized method of P evaluation, which allows obtaining quantitative values for P availability, is the basis for optimizing the dietary P concentration in broiler diets. The major objective of this thesis was to compare various methodological approaches that are used internationally to determine P availability in terms of their suitability. Therefore, firstly the P availability of two mineral phosphates was determined in 3- and 5-wk-old broilers based on data for P retention and prececal digestibility. The P availability of both mineral sources was calculated for both ages of birds by regression analyses for comparison of both response criteria. Secondly, the tibia bone ash and other bone criteria were determined. A comparison of these bone response criteria was then carried out by relating these data to measurements made on P retention. Thirdly, the suitability of tibia P retention for the estimation of the whole body P retention was investigated at both ages of birds. Variation in P retention of birds in these studies was additionally caused by the level and the source of P in the diet. In a fourth study, the effect of the basal diet composition on the availability of a feed phosphate was investigated based on quantitative P retention. A phytin-containing corn-SBM-based as well as a purified basal diet was used. Moreover, the impact of the inorganic phosphate level on the IP6 hydrolysis of the corn-SBM-based diet was assessed on the basis of excreta collection. In the first study, a corn-SBM-based basal diet was used (0.35% P on dry matter basis). MSPa or DCPa was supplemented to increment the P concentration by 0.08%, 0.16%, and 0.24%. Two balance trials (n=8 birds per diet) and two digestibility trials (n=8 pens with 10 birds per diet) were conducted (8 treatments per diet). In 3-wk-old broilers, P retention for MSPa was 70% and significantly higher (P < 0.001) than for DCPa (29%), as calculated by linear regression analysis. Values determined for P pc digestibility at the same age were very similar (67% for MSPa and 30% for DCPa; P < 0.001). In 5-wk-old broilers, P retention was 63% (MSPa) and 29% (DCPa) (P < 0.001), and pc digestibility was 54% (MSPa) and 25% (DCPa) (P = 0.002). In conclusion, in 3-wk-old broilers results obtained with both approaches were the same. In 5-wk-old broilers, the ranking of the two P sources was the same for both approaches. Values differed not greatly between the two age periods. The second study was linked to the first one, and the experimental design was the same. The study comprised two periods with birds of different ages, but from the same hatch. The response criteria evaluated were tibia, tarsometatarsus, toe ash, and P, as well as the Quantitative Computed Tomography measurements of tibiae, blood Pi concentration, and body weight gain. Responses were evaluated and compared based on linear regression analysis. In general, MSPa had a greater slope than DCPa for all criteria studied. For the different bones, the ratio of slopes was very similar based on the amount of ash in both periods. Foot ash was proved to be as sensitive as tibia ash in both periods. Blood serum Pi and body weight gain were not sufficiently sensitive criteria for P evaluation. We concluded that the ranking of both mineral P sources based on bone criteria differed from the ranking that was based on P retention or pc digestibility. The third study was also linked to the first one. Thus, the experimental design was the same. On days 21 and 35, two chicks per treatment were randomly chosen. Contents of P and Ca were determined in tibiae-free bodies and tibiae. The whole body P to tibia P ratio was 21.3±1.3 at d 21 and 19.8±1.1 at d 35 of age. The slope of linear regressions between the tibia P and the whole body P for both ages was identical (17.7). Results indicated that changes in tibia P may be suitable to predict changes in whole body P retention. In the last experiment, a phytin-containing as well as a purified basal diet, both containing 1.8 g available P per kg feed dry matter, was supplemented with MSPa to increment the P concentration by 0.05%, 0.1%, and 0.15%. A retention trial with excreta collection from d 20-24 was conducted (n=7 birds per diet). The level of P did not significantly affect the total P retention either of the corn-SBM-based or of the purified basal diet (P > 0.05). However, increasing the P level significantly reduced (P = 0.015) the IP6 hydrolysis for the corn-SBM-based diets. Percentage P retention for MSPa was calculated by linear regression analysis. P retention for MSPa was 50% for the corn-SBM-based diet and 51% for the purified diet. We concluded that there was no difference in P retention from MSPa between corn-SBM-based and purified diets. It can be concluded from the results of the present thesis that both retention and pc digestibility can be used for evaluating mineral P sources in broilers based on a regression approach. The ranking of mineral P sources based on bone criteria differed from the ranking that was based on P retention or pc digestibility. There was no difference in P retention from MSPa between corn-SBM-based and purified based diets, but a significant effect of the P-level on the IP6 hydrolysis in corn-SBM-based basal diets was found.
Factors influencing the response of broiler chicken to glycine supplements in low crude protein diets
(2016) Siegert, Wolfgang; Rodehutscord, Markus
The increasing demand for meat and other animal products along with the global limitation of arable land for crop production is expected to result in a shortage of protein-rich feedstuff. Furthermore, the excretion of nitrogenous compounds has negative effects on the environment because of the risk of nitrogen (N) leakage into the groundwater. Ammonia emissions from livestock enterprises have been associated with environmentally damaging effects. The biggest determinant of ammonia emissions associated with livestock farming is excretion of N. Excretion of N in part is inevitable but N excretion can be reduced by avoiding excessive intake of feed protein. At present, there is a substantial lack of knowledge about the requirement of nitrogenous nutrients except for essential amino acids (AA) and the influence of these nutrients on animal physiology. As reported in the literature, this has often led to undesirable effects of low crude protein (CP) diets on growth. This partly is due to a deficient glycine (Gly) and serine (Ser) supply in low CP diets. This thesis focused on factors influencing the response to Gly and Ser in low CP broiler feed because growth response to these AA was inconsistent in the literature. In the first study, a meta-analysis was conducted to investigate the response of broilers to dietary levels of Gly equivalents (Glyequi) of Gly and Ser in existing literature. A curvilinear relationship between Glyequi and daily gain (ADG), daily feed intake (ADFI) and feed efficiency (G:F) was found. The impact of dietary Glyequi on ADFI was low, but G:F and ADG varied markedly at different levels of Glyequi. The effect of dietary Glyequi depended on the supply of both methionine (Met) and cysteine (Cys). The G:F and ADG response to dietary Glyequi was different for different Met:(Met+Cys) ratios and Cys concentrations. This was explained by a decreased necessity of conversion of Met to Cys, for which Ser is needed. Adequate concentrations of both Met and Cys probably reduced the necessity of the conversion of Met to Cys. The second study investigated the effect of threonine (Thr) and choline, which are endogenous precursors of Gly, on the response to dietary Glyequi. An increase in Thr concentration reduced the Glyequi concentration required to achieve certain response levels of G:F and ADG. Choline also exerted a considerable effect, but the Glyequi replacing effect of choline was less pronounced than Thr. The observed replacement values of dietary Thr and choline for dietary Glyequi exceeded the possible replacement values calculated by considering endogenous conversion. This likely originated from an excess supply of other essential AA than Thr. If Thr and, to a lower extent, choline limited growth, then excessive intake of other AA had to be catabolized, resulting in an increased need for Glyequi for uric acid formation. It was concluded that further studies should take Glyequi, choline, and Thr together into consideration when determining the requirements for these nutrients. The third study aimed to investigate whether the growth performance and N utilization of broilers are influenced by different proportions of free and peptide-bound AA in diets, and if his influences Glyequi requirements. The hypothesis was that an increased oxidation of free AA leads to an increased ammonia production, which must be detoxified to uric acid in a Gly-dissipating process. 2×2 factorial arrangements were used where one factor was AA from soy protein isolate or from a free AA mix. The other factor was a low and high level of Glyequi. Replacing AA from the soy protein isolate with free AA reduced ADG and G:F, mainly due to reduced ADFI. Reasons for that cannot be identified clearly. The N efficiency on day 21 was not different between the AA sources, possibly due to the lower AA digestibility of the soy protein isolate and higher urinary excretion of nitrogenous substances in the treatments with the AA mix. Thus, availability of AA for protein synthesis after ingestion probably did not limit broiler growth. The ADG of the treatments with the high Glyequi concentration was higher for both AA sources. This increase was due to higher ADFI by broilers in the treatments with soy protein isolate and due to the increased G:F in the treatments with the AA mix. Contrary to the hypothesis, these responses did not give an indication of different utilization of Glyequi for uric acid synthesis. In conclusion, the response of broiler chicken to dietary Glyequi depends on other dietary characteristics, like the concentrations of Cys, Thr, and choline. The information described in this thesis contribute to enable further optimization of the dietary Glyequi concentration as well as the other dietary characteristics influencing the response to Glyequi. This enables reducing the CP concentration in diets without adverse effects on growth and, therefore, diminishing the negative effects of broiler production on the environment.
Feed clusters according to In Situ and In Vitro ruminal crude protein degradation
(2023) Okon, Paul; Bachmann, Martin; Wensch-Dorendorf, Monika; Titze, Natascha; Rodehutscord, Markus; Rupp, Christiane; Susenbeth, Andreas; Greef, Jörg Michael; Zeyner, Annette
Effective degradation (ED) of crude protein (CP) was estimated in vitro at 0.02, 0.05 and 0.08 h−1 assumed ruminal passage rates for a total of 40 feedstuffs, for which in situ ED was available and used as reference degradation values. For this, the Streptomyces griseus protease test was used. The differences between in vitro CP degradation and the in situ CP degradation values were lowest in legume grains and highest in cereal by-products and barley. The differences between in situ and in vitro ED were expressed using a degradation quotient (degQ), where degQ = (EDin vitro − EDin situ)/EDin situ. Among the tested feedstuffs, eight specific clusters were identified according to degQ for the assumed passage rates. The feedstuffs clustered in an unspecific way, i.e., feedstuffs of different nutrient composition, origin or treatment did not necessarily group together. Formaldehyde–treated rapeseed meal, soybean meal, wheat, a treated lupin, sunflower meal and barley could not be assigned to any of the clusters. Groupwise degradation (range of degQ for assumed passage rates are given in brackets) was detected in grass silages (−0.17, −0.11), cereal by-products together with sugar beet pulp (−0.47, −0.35) and partly in legume grains (−0.14, 0.14). The clustering probably based on different specific nutrient composition and matrix effects that influence the solubility of feed protein and limit the performance of the protease. The matrix can be affected by treatment (chemically, thermally or mechanically), changing the chemical and physical structure of the protein within the plant. The S. griseus protease test had reliable sensitivity to reflect differences between native feedstuffs and treatments (thermally or chemically) that were found in situ. The in situ results, however, are mostly underestimated. The clustering results do not allow a clear conclusion on the groupwise or feed-specific use of carbohydrate-degrading enzymes as pre- or co-inoculants as part of the S. griseus protease test and need to be tested for its potential to make this test more conform with in situ data.
Fermentations- und Syntheseleistung der mikrobiellen Gemeinschaft des Pansens in vitro bei Variation der Grobfutter- und Stickstoffquellen
(2017) Zuber, Karin Helga Renate; Rodehutscord, Markus
In the first part of this doctoral thesis five batches of maize silage (MS), five batches of grass silage (GS) and three batches of alfalfa silage were incubated in the Hohenheim gas test. The variation of silages based on in vitro gas production kinetics and ammonia-nitrogen-concentration (NH3-N-concentration) in the mixture of rumen liquid and buffer solution over time was determined. For this purpose, 10 glass syringes per silage batch were used per experimental run. 3 glass syringes were used to determine the gas volume over 72 hours. The remaining 7 glass syringes were removed from the incubator at 7 time points and the NH3-N-concentration in the mixture of rumen liquid and buffer solution was determined. Upon the incubation of the 13 silages both silage species and batch had an influence on the potential gas production and on the rate constant of gas production. The determined potential gas production was between 62.5–74.2, 56.0–64.9 and 39.9–59.6 mL/200 mg organic matter (OM) for MS, GS and alfalfa silages. The rate constant of gas production amounted to 5.5–7.3, 3.8–7.1 and 5.0–7.7 %/h for MS, GS and alfalfa silages. Both silage species and batch as well as the time point and their interactions had an influence on the NH3-N-concentration in the mixture of rumen liquid and buffer solution. In the second part of this work one MS and one GS were incubated in the rumen simulation Rusitec. The influence of the forage source without supplementation of concentrates on the NH3-N-concentration in fermenter liquids over time and the fermentation and synthesis characteristics of the ruminal microbial community were investigated in vitro. Degradation of nutrients, gas, methane and short chain fatty acid (SCFA) production as well as NH3-N in effluent and microbial protein synthesis (MPS) were measured. The NH3-N-concentration in fermenter liquids was determined at different time points within two periods. Upon the incubation of GS, degradation of OM and fibre fractions, amount of NH3-N in the effluent as well as MPS and its efficiency (EMPS) was higher than with incubation of MS. Degradation of crude protein (CP) and total amount of SCFA were unaffected by silage. N-efficiency was higher with incubation of MS than with incubation of GS. During period 1, NH3-N-concentration in fermenter liquids increased for all treatments within the first 24 hours and was not different between the treatments. For GS, NH3-N-concentration subsequently continued to rise up to a maximum value at the last time point of measurement in period 1. NH3-N-concentrations in fermenter liquids in period 2 remained on a relatively constant level for MS and GS, differing between the two silages at all five time points of measurement. Mean NH3-N-concentration in fermenter liquids measured in period 2 corresponded in level with NH3-N-concentration determined in the effluent of both silages. In the third part of this work, the influence of different N-supplements to MS compared to GS on fermentation and synthesis characteristics of the ruminal microbial community in vitro was investigated. GS and MS were incubated in a Rusitec, the latter being either unsupplemented or supplemented with urea, pea protein, pea peptone or a mixture of amino acids to adjust N-content of MS to that of GS. The NH3-N-concentration in fermenter liquids was determined 0, 2, 4, 12 and 24 hours after changing the feed bag on day 12. Results concerning degradation of OM, CP and N-free extracts showed a positive influence of N-supplementations except for MS+pea protein. Furthermore, degradation of detergent fibres were partially improved through N-supplementations. The values of MPS and EMPS were enhanced through all N-supplementations. Thereby supplementation of urea and pea peptone to MS resulted in the largest increase in EMPS. However, through none of the N-supplements the level of GS in EMPS could be achieved. The determined course of NH3-N-concentration in fermenter liquids was largely similar between the treatments. Variation in nutrient composition of MS, GS and alfalfa silages were reflected in a large variation both in gas production kinetics and curve shape of NH3-N-concentration in the mixture of rumen liquid and buffer solution. Upon the sole incubation of MS and GS in the Rusitec, GS promoted MPS and EMPS stronger than MS. Supplementation of MS with different N-sources resulted in an increase in MPS and EMPS compared to MS without N-supplementation. Thus the assumption of an insufficient N-supply of ruminal microbes during the sole incubation of MS in vitro was confirmed. However, through none of the N-supplementations level of GS in EMPS could be achieved.
In vivo and in vitro studies of degradation of inositol phosphates in the digestive tract of broiler chickens
(2017) Sommerfeld, Vera; Rodehutscord, Markus
Phosphorus (P) is an important element in poultry nutrition, which must be adequately supplied in the diet. However, for non-ruminant animals, it is only partially available from plant seeds—the major components of poultry diets—where P is predominantly bound as phytic acid (myo-inositol 1,2,3,4,5,6-hexakis (dihydrogen phosphate); InsP6) and its salts, called phytate. InsP6-P can be utilized after the stepwise cleavage of the P from the phytate molecule by phytases and other phosphatases. After the theoretical complete dephosphorylation of InsP6, six phosphate groups and myo-inositol (MI) are potentially available for absorption. Recent studies assume an effect of MI on growth performance when it is added in its free form to the diet or released as a result of InsP6 breakdown. Because P is of specific economic and environmental relevance, the improvement of the digestibility of plant P in poultry is of great interest. The overarching aim of this thesis was therefore to gain a deeper insight into the degradation of InsPs in the digestive tract of broiler chickens, with a focus on the intermediate and end-products as influenced by the diet composition. An in vitro assay was established to study the disappearance of InsP6 and the formation of lower inositol phosphate (InsP) isomers in the poultry digestive tract. The assay simulates the conditions (pH, temperature, proteolytic enzymes, water content, and retention time) of the crop, stomach, and small intestine, using a poultry diet as matrix. The assay yielded highly reproducible results and was sensitive to the factors that varied in the three experiments. A diminishing effect on InsP degradation was found by the supplementation of P and Ca. The described assay is a suitable tool that can be used to screen feed enzymes and to investigate the effects of supplements in the absence of endogenous phytases. The first in vivo experiment aimed to distinguish between the single and interactive effects of P, calcium (Ca), and phytase. Effects on lower InsP esters and their isomers and MI in different segments of the digestive tract, and on the prececal digestibility of P, Ca, and amino acids (AAs) in broiler chickens were studied. Moreover, a complete picture was drawn of all dephosphorylation steps from InsP6 to MI in the digesta of the terminal ileum. The dietary treatments included diets without (P-) or with (P+) monosodium phosphate supplementation, without (Ca-) or with (Ca+) additional limestone supplementation, and without or with 1500 FTU phytase/kg feed. Up to the terminal ileum, InsP6 disappearance was found to decrease in P+Ca-, and even more so in P+Ca+, when no phytase was added. Adding phytase removed all effects of P and Ca. However, P+Ca+ increased the concentrations of lower InsP esters and reduced free MI in the ileum, even in the presence of phytase. Supplementation with phytase increased the concentration of MI in all segments of the digestive tract and in blood plasma, demonstrating the ability of broilers to fully degrade phytate and absorb the released MI. While the prececal AA digestibility was not affected by P and Ca or an interaction between P, Ca, and phytase, it increased with the addition of phytase. The objective of the second in vivo experiment was to investigate the effects of supplementation with free MI or graded levels of phytase on InsP degradation, concentrations of MI in the digestive tract and blood, bone mineralization, and prececal digestibility of AA. Birds were fed a control diet with adequate levels of all nutrients without or with MI supplementation, or one of three experimental diets that differed in phytase level, with reduced P and Ca levels. These outcomes indicate that MI might have been a relevant cause for the increase in gain:feed. Therefore, it is likely that the release of MI after complete dephosphorylation of phytate is one of the beneficial effects of phytase, along with the release of P and improvement in digestibility of other nutrients. It can be concluded that the established in vitro assay is a suitable tool to investigate effects on feed enzymes or differences between different feed enzymes in a feed matrix under standardized conditions without the interference of endogenous phytases, or depending on animal-specific variations. Based on the outcome of the in vitro and in vivo experiments of the present project, the combined supplementation of P and Ca—rather than supplementation of P or Ca solely—seems to be crucial for InsP degradation. There is now some evidence that MI can affect the growth and feed efficiency of broiler chickens without affecting the metabolism of InsPs or AAs. As the results regarding the effects of P and Ca on InsP6 degradation or phytase effects on AA digestibility are not consistent across studies, and studies investigating the effects of MI are scarce and not consistent, further systematic research is needed.
Investigations on factors influencing the response of broiler chickens to low crude protein diets with specific regard to nonessential amino acids
(2020) Hofmann, Philipp; Rodehutscord, Markus
Nitrogen (N) excretion caused by animal husbandry can have negative effects on the environment. Lowering dietary crude protein (CP) concentrations can reduce these negative impacts by lowering the N excretion of the animals. However, reduction of dietary CP concentrations for broiler chickens may be accompanied by reduced growth. This thesis focused on the effects of dietary CP reduction on growth of broiler chickens and influencing factors that need to be considered in low CP diets. The first study was carried out to investigate to what extent dietary CP concentrations can be reduced when dietary glycine equivalent (Glyequi) and essential amino acid (AA) concentrations are adequately supplied. Further, it was the aim to determine the response of broiler chickens to dietary Glyequi concentrations at varying CP levels. Ten male broiler chickens each were housed in 1 of 84 metabolism units. Diets with three CP levels of 16.3% (CP16.3), 14.7% (CP14.7), and 13.2% (CP13.2) each containing four Glyequi concentrations of 12, 15, 18, and 21 g/kg were used. Quantitative excreta collection was carried out from days 18–21. The reduction of dietary CP concentrations decreased average daily gain (ADG) and gain:feed ratio (G:F) from days 7–21 and increased the nitrogen-utilization efficiency (NUE). Supplementation of Glyequi increased ADG and G:F at CP13.2. The ADG at CP14.7 and G:F at CP14.7 and CP16.3 increased up to 15 g Glyequi/kg. These results indicated that the minimum to which dietary CP concentrations can be reduced in broiler chickens up to three weeks of age is between 16.3 and 14.7% when dietary Glyequi and essential AA are adequately supplied. Further, these findings showed that the growth-response of broiler chickens to dietary Glyequi is influenced by dietary CP concentrations. The second study was conducted to determine whether supplementation of single nonessential AA (neAA) can diminish or overcome the growth-decreasing effect of a diet with reduced dietary CP and neAA concentrations. Further, the effect of non-protein nitrogen supplementation in a diet with insufficient neAA concentrations was investigated. Nine male broiler chickens each were kept in 1 of 81 metabolism units. Two diets with different neAA concentrations, except Glyequi, and adequate essential AA concentrations were mixed resulting in CP levels of 17.8% (CP17.8), and 15.6% (CP15.6). The dietary Glyequi concentration was 15 g/kg in each diet. Other diets were mixed by supplementing either L-Alanine, L-Proline, L-Aspartic acid, a mix of L-Aspartic acid and L-Asparagine·H2O, L-Glutamic acid, or a mix of L-Glutamic acid and L-Glutamine to CP15.6 to achieve the respective neAA concentration of CP17.8. Ammonium chloride (NH4Cl) was added to CP15.6 to achieve the CP concentration of CP17.8. Excreta were collected quantitatively from days 18–21. Highest ADG and G:F from days 7–21 were found at CP17.8 and decreased at CP15.6. Supplementation of aspartic acid and asparagine (Asp+Asn), glutamic acid (Glu), and glutamic acid and glutamine (Glu+Gln) increased ADG and G:F to a similar extent, but not to the level of CP17.8. The NUE was highest at CP15.6, and CP15.6 supplemented with alanine, proline, and Glu. Lower NUE was observed at CP17.8 than at CP15.6 without and with neAA supplementation. Overall lowest ADG, G:F, and NUE were found upon NH4Cl supplementation. These findings showed that individual supplementation of Asp+Asn, Glu, and Glu+Gln could partly overcome the growth-reducing effect of very low CP diets. NH4Cl was found unsuitable to increase growth. The aim of the third study was to investigate interactive effects among dietary Glyequi, cysteine (Cys), and choline (Cho) on the growth of broiler chickens. Ten male broiler chickens each were housed in 105 metabolism units. Excretion of N was determined from days 18–21. Five levels each of dietary Glyequi, Cys, and Cho were tested in 15 dietary treatments. Another diet was provided to 15 birds each in another 5 metabolism units to measure prececal AA digestibility. The G:F from days 7–21 increased with digestible Glyequi intake. Differences between low- and high-digestible Cys intake were low. Hardly any effect of Cho intake on G:F was found compared to digestible intake of Glyequi and Cys. The NUE was very high with low variation among treatments. These results showed that the interactive effects among dietary Glyequi, Cys, and Cho on growth were slightly pronounced. This was likely an effect of high NUE and its low variation that caused the Glyequi requirement to be low. In conclusion, the lowest level to which dietary CP for broiler chickens up to three weeks of age can be reduced is between 16.3 and 14.7%. The growth-decreasing effect of a diet with reduced neAA concentrations can be slightly overcome upon supplementation of Asp+Asn, Glu, and Glu+Gln. Moreover, dietary CP concentrations and the related amounts of excreted N influenced the response of broiler chickens to dietary Glyequi.
Investigations on nutritional characteristics of microalgae with emphasis on ruminants
(2019) Wild, Katharina Judith; Rodehutscord, Markus
The main objective of the present thesis was to systematically determine nutritional characteristics of microalgae and evaluate the suitability of microalgae as feedstuffs, particularly for ruminants. The experiments comprised a comprehensive characterisation of microalgae nutrient profiles with chemical-analytical methods and the determination of extent and dynamics of nutrient utilization using in vitro methods. In order to generate a comprehensive database on nutrient composition of microalgae, 16 commercial microalgae biomasses of four genera (Arthrospira, Chlorella, Nannochloropsis, and Phaeodactylum) were analysed utilizing established methods for food and feed evaluation (Manuscript 1). These investigations included determination of the in vitro crude protein (CP) digestibility for pigs. Nutrient analyses showed a considerable variation particularly in concentrations of proximate nutrients, minerals, and fatty acids, both among and within genera. This variation presumably resulted from varying cultivation conditions and it was concluded that general mean values are not appropriate to characterize microalgae in terms nutrient composition. Manuscript 2 aimed to determine characteristics of the nutritional value of microalgae for ruminants utilizing different in vitro methods. The commercial biomasses included in Manuscript 1 were investigated using the Hohenheim Gas Test method. The investigations comprised the determination of several ruminal fermentation characteristics, of the energy value, and of the protein value. A three-step enzymatic in vitro system was used to estimate intestinal digestibility of ruminally undegraded CP (IDP). Ruminal fermentation of the investigated microalgae biomasses was overall low, which was indicated by an overall low level of production of gas and volatile fatty acids, and a low ruminal CP degradation. As a result of low ruminal fermentation, microalgae biomasses were characterized by high concentrations of ruminally undegradable CP (RUP; 386, 399, 315, and 263 g RUP/kg DM at passage rate of 8 %/h for Arthrospira, Chlorella, Nannochloropsis, and Phaeodactylum, respectively). Thus, microalgae appear to be potential alternative protein sources for high performing animals. However, this was contradicted by low IDP, which was determined for microalgae in the present thesis for the first time (mean values for Arthrospira, Chlorella, Nannochloropsis, and Phaeodactylum were 27, 43, 43, and 40 % of RUP respectively). The variation observed in nutrient profiles was reflected in several nutritional characteristics. A common objective of Manuscript 1 and Manuscript 2 was to investigate whether cell disruption affects nutritional characteristics of microalgae. In Manuscript 1, effects of cell disruption on in vitro CP digestibility for pigs were investigated and in Manuscript 2 several in vitro methods were utilized to investigate effects of cell disruption on the nutritional value of microalgae for ruminants. Mechanical cell disruption with a ball mill enhanced in vitro CP digestibility and ruminal fermentation in most of the samples, presumably by the destruction of cells and hence an increase in nutrient accessibility. Nevertheless, concerning the protein value of microalgae in ruminants, application of mechanical cell disruption cannot not be recommended because it decreased RUP but did not increase IDP so that intestinal digestible RUP was overall decreased by cell disruption. The aim of the third manuscript was to investigate the effects of variable cultivation conditions on nutrient composition and nutritional characteristics for ruminants of the microalgae Chlorella vulgaris. Chlorella vulgaris was cultivated under varying conditions (saturation, nitrogen and CO2 depletion, outdoor cultivation). The obtained biomasses were analysed for their nutrient composition and their nutritional value for ruminants using different in vitro methods. Both, nutrient composition and characteristics of the nutritional value for ruminants were affected by the cultivation process. Nutrient deficient conditions had rather adverse effects in terms of digestibility, protein value, and nutrient productivity. It can be concluded that microalgae have potential as alternative protein source for ruminants. Nevertheless, this potential is contradicted by low IDP, but the findings obtained herein have to be verified in future studies. Furthermore, the results of the present thesis show that nutrient composition and ruminal fermentation characteristics of microalgae vary considerably between and in many cases even within microalgae genera. Thus, to the extent possible, it should be strived for a standardisation of cultivation conditions, in order allow better predictions of nutritional characteristics of microalgae.
Investigations on phytate degradation of rapeseed meal and soybean meal in ruminants
(2023) Chi, Yung-Ping; Rodehutscord, Markus
Oilseed meals are widely used protein feeds in ruminant nutrition. However, aside from the high crude protein (CP) content, oilseed meals also contain high amounts of phosphorus (P), which is predominantly present in organic form as different salts of myo-inositol 1,2,3,4,5,6 hexakis dihydrogen phosphate (InsP6). To become available for intestinal absorption and further utilisation by animals, P must be cleaved from the InsP6 molecule by a specific group of phosphatases, which is known as phytase. Over the decades, ruminants were considered to be capable of utilising nearly all P bound in InsP6 because of the substantial phytase activity exhibited by rumen microbiota. Nevertheless, recent studies have reported variable extents of ruminal InsP6 degradation which seems to be influenced by different factors. In case of an incomplete ruminal InsP6 degradation, post-ruminal InsP6 degradation may be of higher relevance. However, post-ruminal InsP6 degradation has been rarely studied to date. The aim of this thesis was to systematically investigate InsP6 degradation of rapeseed meal (RSM) and soybean meal (SBM) in ruminants, including the possible influencing factors and their combinations. Different study methods (in vivo, in situ, and in vitro) were applied to evaluate the effects of RSM and SBM. The first study (Manuscript 1) was conducted to investigate ruminal and post-ruminal InsP6 degradation in wethers fed a diet containing RSM or SBM, and to link the ruminal disappearance determined in slaughtered wethers with in situ calculated rumen effective degradation of InsP6 (InsP6ED) from cows. Firstly, RSM and SBM was incubated according to a standard in situ procedure in three lactating Jersey cows for 2, 4, 6, 8, 16, 24, 48, and 72 h to obtain InsP6ED for the oilseed meals at rumen passage rates of 0.02 (InsP6ED2) and 0.05 h-1 (InsP6ED5). Secondly, eight wethers were randomly assigned to two treatment groups that were fed a diet containing equal amount of RSM (Diet RSM) or SBM (Diet SBM) for 8 weeks of adaptation. Then, digesta from the reticulo-rumen, omasum, abomasum, jejunum, colon, and rectum were sampled. In consistence with in situ calculated InsP6ED2 (83 and 93% for RSM and SBM, respectively), ruminal InsP6 disappearance was lower in wethers fed Diet RSM (76%) compared to those fed Diet SBM (89%). Post-ruminal InsP6 disappearance did not differ between dietary treatments (6% for Diet RSM vs. 4% for Diet SBM). A higher amount of ruminally degraded InsP6 was observed upon feeding RSM (4.5 g/d for Diet RSM and 3.4 g/d for Diet SBM). Due to the low rumen passage rate in this study, it was suggested that P from InsP6 being available to ruminants is almost entirely from InsP6 degradation in the rumen. As InsP6 is located in a protein-rich structure in seeds and InsP6 degradation has been recently reported to vary in a pattern similar to CP degradation for RSM, the second study (Manuscript 2) was carried out to investigate the variation of in situ ruminal InsP6 degradation of SBM and its relation to CP degradation. In this study, nine commercial solvent-extracted SBM from Europe and South America were incubated in three rumen-fistulated lactating Jersey cows with the same procedure performed in the first study. Rumen effective degradation of CP and InsP6 were calculated for a rumen passage rate of 0.06 h-1 (CPED6 and InsP6ED6). Chemical protein fractions of SBM variants were determined according to Cornell Net Carbohydrate and Protein System (CNCPS). The SBM variants exhibited a considerable variation in CP and InsP6 degradation. Significant correlations were found between InsP6ED6 and CPED6 and between InsP6ED6 and all CNCPS protein fractions, which confirmed the close relationship between CP and InsP6 degradation for SBM. The results suggested that using a general value of InsP6 degradation for diet formulation may not be precise enough, and InsP6ED may be predicted based on CPED or CNCPS protein fractions by using linear regression equations. The third study (Chapter 4.3) aimed to achieve a better understanding of how in vitro InsP6 degradation of RSM and SBM is influenced by different amounts of InsP6 in feed. The same batches of RSM and SBM as used in Manuscript 1 were incubated in a modified rumen simulation technique (RUSITEC) system with different amounts for 3, 6, 12, 24, and 48 h. Degradation of InsP6 from bag residues was calculated and expressed as amount and in percentage using the same equation as applied for in situ calculations. In vitro degradation of InsP6 in response to InsP6 amount differed between RSM and SBM, which may be attributed to the different internal structure and nutrient composition of the oilseed meals. Only when expressing in amounts, the calculated InsP6ED was observed to increase linearly with increasing InsP6 amount in feed. Accordingly, it was recommended to compare InsP6 degradation based on InsP6 amount in the feed and to express degradation as amount instead of using relative value which might not reflect the real degradation kinetics. In conclusion, the results of this thesis showed that the extent of ruminal InsP6 degradation differs when the diet contains either RSM or SBM, while post-ruminal InsP6 degradation is negligibly low given a long rumen retention time. By using linear regression equations, ruminal InsP6 degradation may be predicted from CP degradation due to the close relationship therebetween. Effects of InsP6 amount on InsP6 degradation is dependent on InsP6 source. Based on the high similarity among ruminal InsP6 degradation determined by different methods in this thesis, ruminal InsP6 degradation of oilseed meals measured by in situ or in vitro study may be applicable for in vivo conditions.
Investigations on ruminal degradation of nutrients and feeding values of single feeds and compound feeds for cattle
(2020) Grubjesic, Goran; Rodehutscord, Markus
The environmental impact of intensive animal farming has been steadily increasing. Cattle can contribute to environmental pollution due to relatively low nitrogen (N) and phosphorus (P) utilisation, leading to their excess excretion. High-yielding dairy cows are commonly fed concentrate compound feed, in mash or pelleted form, to satisfy high protein and energy requirements. Main source of energy in concentrate compound feeds is starch (ST). For the accurate formulation of compound feeds, comprehensive insight into nutritive values of single feeds as well as their potential interactions (associative effects) when mixed is needed. Typically, the nutritive values of single feeds are considered to be additive, assuming that no associative effects exist. However, data supporting such assumption for concentrate feed are scarce. The present thesis had two aims: evaluation of additivity of ruminal degradation of nutrients and feeding values of single concentrate feeds in compound feeds, and evaluation of effects of pelleting on ruminal degradation of nutrients and feeding values of compound feeds. Twelve single feeds were used to formulate eight compound feeds in different combinations, targeting crude protein (CP) concentrations from 16 to 30% in dry matter (DM). Compound feeds were prepared both, in mash and pellet form in a commercial feed mill using standard industrial conditions. Ruminal degradation of single and compound feeds was evaluated using in situ and different in vitro techniques. The in situ incubations were conducted by incubating samples of all single and compound feeds in polyester bags for 2, 4, 6, 8, 16, 24, 48, and 72 hours in three ruminally fistulated dairy cows. Bag residues were analysed and the ruminal effective degradability (EDIN_SITU) of CP and ST, was calculated for passage rates of 5 and 8%/h. Phosphorus is located in plants as phytate (InsP6), and for some feed samples the EDIN_SITU of InsP6 was also determined. The in vitro gas production (GP), digestibility of organic matter (dOM), metabolisable energy (ME), and utilisable CP at the duodenum (uCP) were evaluated using Hohenheim Gas Test and extended HGT. Intestinal digestibility (IDRUP) of ruminally undegraded protein (RUP) was determined using a three-step enzymatic method through incubation with pepsin and pancreatin. Chemical fractionation of CP was performed according to the Cornell Net Carbohydrate and Protein System (CNCPS) The CP fractions can be also used to predict EDIN_SITU. Assessment of additivity was performed by comparing the observed values of compound feeds with values for compound feeds calculated from single feeds. It was concluded that additivity of single feeds in mash compound feeds was given for EDCPIN_SITU, EDSTIN_SITU (Manuscript 1), uCP, CP fractions, GP, and dOM (Manuscript 2). Here, associative effects among single feeds were considered to be small and should not affect formulation of concentrate compound feeds. The GP and proximate nutrients are necessary to estimate ME using appropriate equations, often specific for feed or feed type. The additivity of ME was given only when same ME equation for single and compound feeds was used. Additivity was not given for IDRUP (Manuscript 2). Pelleting had overall small effects on feeding values of compound feeds determined in situ and in vitro (Manuscripts 1 and 2). Presumably, the relatively low intensity of heating (up to 80–90°C) during the pelleting process was not sufficient to significantly affect nutritive value of compound feeds, with the exception of decreased IDRUP. Overall, it was concluded that additivity of ruminal degradation of nutrients and feeding values of single feeds in mash and pelleted compound feeds can be assumed for practical feed formulation. While some associative effects were detected, they might be related to methodological causes in most of the cases.
Investigations on the effects of forage source and feed particle size on ruminal fermentation and microbial protein synthesis in vitro
(2012) Hildebrand, Bastian; Rodehutscord, Markus
The synthesis of microbial protein in the rumen has a major impact on protein- and amino acid supply in ruminants. The amount and amino acid composition of the protein that enters the small intestine primarily depends on diet formulation. In the present studies the effects of maize silage (MS) and grass silage (GS) on ruminal fermentation and microbial protein synthesis were investigated, considering methodical aspects of in vitro studies, particularly grinding of feed samples. In the first experimental series five mixed diets with different proportions of MS and GS (100:0, 79:21, 52:48, 24:76 and 0:100) and a constant proportion of soybean meal (11%) were used. The content of crude protein (CP) and fibre fractions increased, whereas the content of organic matter (OM) and starch decreased with increasing proportion of GS in the diet. It was hypothesised that a combination of MS and GS can benefit microbial growth and thus fermentation of nutrient fractions to a higher extent than using only one forage source separately. It was also to be investigated how changes in diet composition affect the amino acid profile of microbial protein. A well standardised semi-continuous rumen simulation technique (RUSITEC) was used, which is a commonly accepted experimental model in investigations on ruminal fermentation. Changes in fermentation characteristics, as a result of changing the MS-to-GS ratio, were tested for linear and quadratic effects in order to identify possible associative effects. Prior to the in vitro incubation, feedstuffs were dried and ground. It was aimed to investigate in which way fermentation in the RUSITEC system is influenced by mean feed particle size. Therefore two milling screen sizes (MSS; 1 vs. 4 mm) were used in all diets and results on fermentation characteristic were tested for possible interactions of forage source and MSS. One incubation period lasted for 13 days (6 days adaption period, 7 days sampling period), and each treatment was tested in at least three replicates. Ruminal digesta, obtained from rumen-fistulated wether sheep, was used as the inoculum for starting the incubation. Diets were fed once daily to the RUSITEC system, and nylon feed bags remained for 48 h inside the fermentation vessel. A buffer solution, containing 15NH4Cl, was infused continuously into the vessel and the respective effluent was analysed for short chain fatty acids (SCFA) and NH3-N. Solid- and liquid- associated microbial fractions were isolated from the feed residues, the liquid inside the vessel and the effluent by differential centrifugation. The flow of microbial CP was quantified on the basis of N and 15N balances. The feed residues were analysed for crude nutrients and detergent fibre fractions and the respective degradation rates were calculated. OS and CP in the feed residues were corrected for the contribution of solid-associated microbes. The degradation of OM and fibre fractions, as well as amounts of NH3-N increased linearly with stepwise replacement of MS by GS. Degradation of CP was unaffected by diet composition, as well as total SCFA production. The degradation of OM and CP was higher in coarse milled (4 mm-MSS) than in fine milled (1 mm-MSS) treatments, accompanied by higher amounts of NH3-N and total SCFA. An improvement of growth conditions for some microbial groups, e.g. anaerobe fungi, was discussed. The amount of microbial CP increased linearly by the stepwise replacement of MS by GS, and was higher at 4 mm-MSS than at 1 mm-MSS. The amount of available N was assumed to advance microbial growth in the RUSITEC system. Efficiency of microbial CP synthesis was improved from 29 to 43 mg microbial N per g degraded OM by increasing the proportion of GS in the diet, but was unaffected by MSS. The N content and the profiles of amino acids of the three microbial fractions, as well as the ratio of solid- to liquid-associated microbes were affected by diet composition and MSS. Interactions of forage source and MSS were rare. However, the results indicated interactions between dietary factors and origin of microbial isolate on characteristics of microbial protein synthesis. In order to provide additional information on the nutritional value, the mixed diets were evaluated by two further methods. The total tract digestibility of crude nutrients was determined in wether sheep. The content of metabolisable energy was similar between diets and averaged 11.5 MJ per kg dry matter. The in vitro gas production was measured within 93 h by using a modified Hohenheim gas production test, providing information on kinetics and extent of ruminal fermentation. Cumulative gas production decreased with increasing proportion of GS in the diet. A negative effect of coarse milling on fermentation in the Hohenheim gas production test was confirmed. Across all diets gas production was delayed at 4 mm-MSS compared to 1 mm-MSS. The results from both approaches supported the findings of the RUSITEC study that a stepwise replacement of MS by GS led to a linear response in degradation of nutrients. As indicated by the gas production data, positive associative effects might only occur in the first hours after starting an incubation. When mixed diets are used effects cannot be clearly related to individual diet ingredients. Moreover, in the mixed diets interactions between soybean meal inclusion and forage source or feed particle size cannot be excluded. Therefore pure silages were incubated separately in the RUSITEC system in the second experimental series and three milling screens of different size were used (1, 4 and 9 mm). In accordance with the first experimental series, degradation of OM, fibre fractions and non-structural carbohydrates, production of NH3-N, as well as microbial CP flow and efficiency of microbial CP synthesis were higher in GS than in MS. A higher degradation of CP was found for MS than for GS, indicating interactions between forage source and soybean meal inclusion. An increase in MSS from 1 mm to 9 mm led to an improvement in the degradation of OM, CP and non-structural carbohydrates, particularly of starch in MS, as well as in the microbial CP flow for both silages. But the efficiency of microbial CP synthesis and microbial amino acid profile were less affected by MSS. In the second experimental series additionally the effect of available N on fermentation of MS was investigated. The supplementation of urea-N improved the degradation of non-structural carbohydrates, especially starch, but not that of fibre fractions in MS. The efficiency of microbial CP synthesis was increased from 26 to 35 mg microbial N per g degraded OM by urea-N supplementation to MS. The way of urea administration, either supplied together with the feed once daily or infused continuously by buffer solution, had only marginal effects on fermentation characteristics. It was concluded that microbial growth is improved by degradation of OM from GS compared to MS and by an increasing availability of N in the RUSITEC system. Meaningful associative effects of mixtures of MS and GS on ruminal fermentation characteristics are not likely to occur. However, transferability of results to other batches of MS and GS is limited, as high variations in chemical composition are known for both types of silage. Fermentation of MS- and GS-based diets in the RUSITEC system benefits more by coarse milling at MSS up to 9 mm than by fine milling at 1 mm-MSS. Consequently, variations in MSS and feed particle size distribution have to be taken into account when evaluating feeds by rumen simulation systems. The changes in composition and contribution of microbial fractions give indications to a shift in the microbial community as a result of variation of silage type and feed particle size, but further research on this aspect is needed. Moreover, the present results stated that the origin of the microbial samples is very important for measurements on microbial protein synthesis.
Langfristige Beurteilung der Energieversorgung von Milchkühen bei unterschiedlichem Kraftfuttereinsatz
(2020) Gerster, Elisabeth Katharina; Rodehutscord, Markus
The first objective of the present study was to compile the current knowledge concerning the effect of the amount of CON on dry matter (DM) intake and milk yield of dairy cows, by regression analysis. For this purpose, a dataset was compiled containing 46 studies with feeding trials and graded inclusion levels of CON. When offering the roughage ad libitum, a quadratic relation was found between CON intake and roughage intake. Taking into account the substitution of roughage, the observed increase of milk yield was less than expected. The second objective was to verify the response of Simmental dairy cows to a long-term reduction of the CON input, in terms of dry matter intake, milk yield, and energy supply. During a feeding trial conducted over a two-year period at the experimental station LAZBW in Aulendorf (cooperative research project „optiKuh“) each 24 Simmental dairy cow was fed either 250 (group 250) or 150 (group 150) g CON per kg energy-corrected milk yield (ECM) throughout lactation. Grass and maize silage as well as straw and hay were combined in the total mixed rations to ensure an energy concentration of 6.6 MJ NEL per kg DM of the roughage in both groups throughout lactation. The CON contained a mixture produced on-site (winter wheat, winter barley, faba bean) and rapeseed meal. At 165 days in milk, each cow in both groups was switched individually to a ration containing less CON. Data were gathered also during the dry period. Feed was offered for ad libitum consumption. Statistical analyses were done separately for the lactation and dry period. As fixed effects the calendar week, the group, the parity, and the interaction group*parity entered the model, respectively. Additionally, the days in milk were included as a covariate during lactation. During lactation the mean daily DM intake did not differ significantly between group 250 (21.6 kg DM) and group 150 (21.0 kg DM). The calculated substitution of roughage amounted to 0.75 kg DM per kg CON DM during the mentioned trial period. As lactation progressed, more roughage was substituted. The group 250 had a higher milk yield during the first half of lactation, but a lower milk yield during the second half. The mean milk yield was equal in both groups (28.7 kg ECM per day). The examined blood characteristics (8, 28, 100 days p. p., at drying off, 14 days a. p.) and the milk fatty acids analysis by gas chromatography (5, 28, 100, 200 days p. p.) reflected the different progressions of the energy balance of the two groups. On average the group 250 reached a positive energy balance already at 37 days in milk. Probably owing to a better glucose supply after calving, the serum insulin concentration increased faster and supported the replenishing of body reserves at the expense of milk yield. On the contrary, the group 150 achieved a positive energy balance only after 72 days in milk on average. Indicating the mobilization of body reserves, the blood of group 150 showed a significantly higher D-ß-hydroxybutyrate concentration, and the milk fat a significantly higher concentration of long-chain fatty acids 28 days p.p.. However, the values were within the physiological range. The reduction of CON did not increase the likelihood of illness. During the dry period, despite equal feeding of both groups in this period, the group 150 had an increased DM intake of 0.9 kg DM per day (p=0,026). Thus, they restored body energy reserves. Over time both groups succeeded in balancing the energy deficit of the beginning of lactation. The proposal of SUSENBETH (2018) for the calculation of the energy requirement of dairy cows improved the plausibility of the calculated energy balances compared with the factors according to GfE (2001). The third objective was to develop a model for the estimation of energy balance in the first third of lactation based on characteristics of production with focus on concentration of milk fatty acids. For this purpose, the milk fatty acids analyses 5, 28 and 100 days p. p. of the feeding trial were used (n=200). The model was derived from the regularized linear regression method „elastic net“. The variables milk yield on sampling day, milk fat content, concentrations of the milk fatty acid C12:0 and the milk fatty acid C18:0, as well as the relations n-6/n-3, C15/C17 and oleic acid/C15 were selected. An estimation error of 13.1 MJ NEL per day was determined by leave-one-out cross-validation. Potentially, the model seems to be applicable for the detection of a severe negative energy balance at the beginning of lactation. But first a validation with an independent dataset is required.