Browsing by Subject "In vitro"

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Comparison of plant cell wall degrading community in the rumen of N’Dama and N’Dama x Jersey crossbred cattle in relation to in vivo and in vitro cell wall degradation
(2004) Nouala-Fonkou, Simplice; Becker, Klaus
This thesis presents a unique combination of an in vivo feeding trial, the analysis of the microbial community structure in the rumen, and in vitro fermentation studies, in order to assess the impact of breeds and diets on animal performance in a West African production setting. Pure N?Dama and N?Dama x Jersey crossbred cattle were fed two basal diets, baby corn and groundnut hay, supplemented with graded levels of either conventional concentrate or moringa leaf meal, to compare animal responses in productivity. In this context, Moringa oleifera leaf meal constitutes a locally available, potential alternative to commercial concentrate for cattle production. The cell wall digesting community of N?Dama and its crosses was analysed using phylogenetically based hybridisation probes to account for the contribution of rumen microbes to differences in fermentation patterns and animal response. In vitro fermentation studies were carried out using the same diets and supplementation levels as fed in vivo, to test the accuracy of the in vitro gas production technique in predicting the optimum level of supplementation. The in vivo feeding experiment focussed on the comparison of breed performance with diets relevant for local production conditions. Six N?Dama and six N?Dama x Jersey (crossbred) animals were used in a cross over design. They were fed consecutively three combinations of roughage and supplement, baby corn stover and concentrate (BCS:Co), groundnut hay and concentrate (GNH:Co) and groundnut hay and moringa meal (GNH:Mo), each at 5 levels of supplementation (0, 10, 20, 30 and 40%). Results from this study showed that there was a clear difference in animal response to different feeding regimes between the two breeds. When averaged over all diets organic matter intake (OMI) was higher in crossbred compared to N?Dama (94 and 87.6 g/kg 0.75 d-1, respectively). When analyzed for the diets and averaged over the breeds OMI was higher when animals were fed the baby corn based diet compared to groundnut based diets (95 against 88 g/kg 0.75 d-1). Only when the diet consisted of BCS:Co, and at low levels of supplementation, N?Dama ingested more than crossbred, but the difference was not significant. With GNH:Co crossbred ingested significantly more at levels of supplementation less or equal to 20%. With GNH:Mo crossbred ingested more, whatever the level of supplementation. The optimum level of supplementation in vivo, estimated with the single slope broken line model, was 10% and 20% for both breeds when they were fed BCS:Co and GNH:Co respectively, but 30% for N?Dama and 10% for the crossbreds when animals were fed GNH:Mo. Organic matter digestibility (OMD) was higher in N?Dama (64.6% against 60.7% in crossbreds) when animals were fed BCS:Co and supplementation had no effect on OMD of BCS:Co whatever the breed. When animals were fed groundnut hay as basal diet, OMD was also significantly higher in N?Dama at low levels of supplementation, but the differences became insignificant beyond 10% and 20% of concentrate or moringa, respectively. With GNH:Co OMD showed a quadratic response (p<0.001) with increasing level of supplementation when it was fed to crossbreds and was not affected when it was fed to N?Dama. Increasing levels of moringa meal supplementation increased OMD in both breeds up to a peak at 20 and 30% for N?Dama and crossbred, respectively. Average daily weight gain (ADG) was not affected by the breed, however it was higher on BCS:Co compared to other diets. On BCS:Co ADG increased with the level of supplementation, reaching a peak at 30%, whereas supplementation had no effect on ADG when animals were fed groundnut hay based diets. As N?Dama could take in and digest more of the low quality BCS:Co diet, they were less efficient in feed conversion under this feeding regime (FCE: 14 vs. 9 for the crossbreds). On GNH based diets, however, N?Dama surpassed the crossbreds in feed conversion efficiency with ratios of 11 vs. 13 for GNH:Co and 9 vs. 27 on GNH:Mo. Rumen microbes play the key role for the digestibility of a given feed and thus also for feed intake and finally animal performance. Obviously, the community composition and activity is highly dependent on the diet. With the present set-up, however, with identical external conditions and three different, well defined diets fed to both, N?Dama and crossbred cattle, a comparison of the microbial community structure between breeds could be attempted. The in vivo and in vitro data taken in the other parts of the study allow a sensible interpretation of potential changes in microbial composition. Rumen fluid was collected from three fistulated N?Dama and three crossbred animals adapted to the experimental diets at medium supplementation level. The cell wall degrading community was analyzed using the phylogenetically based 16S rRNA hybridisation probes. The results showed that on BCS:Co diet the Fibrobacter and R. flavefaciens RNA concentrations were higher in rumen fluid of N?Dama compared to crossbred. These concentrations were also significantly affected by the diet, such that they were higher on baby corn stover compared to groundnut hay based diets. The results of the microbial community analysis suggested that the differences between breeds observed in digestibility could be partially explained by the composition of the cell wall degrading community. Parallel to the in vivo experiment, in vitro fermentation studies were undertaken to evaluate the predictability of the in vivo response to supplementation by the in vitro data. Rumen fluid from 3 N?Dama and 3 crossbred donor animals was used for 24 hour in vitro fermentations. The donor animals were fed consecutively the same three diets used in vivo (BCS:Co, GNH:Co and GNH:Mo) at 20% level of supplementation. Each of these inocula was incubated with in vitro substrates consisting of all the combinations tested in vivo (i.e. 3 diets, 5 levels of supplementation) plus supplement alone. This design should allow to analyze for both, the impact of donor breed as well as that of the donor diet and to conclude which factors may be varied while maintaining predictability. The breed of the donor animals did not significantly affect 24 hour gas production, but short chain fatty acid concentration was higher with rumen fluid from crossbreds when donors were fed BCS:Co and GNH:Mo. Moringa meal as supplement to donor animals changed the fermentation pattern of all the substrates, such that gas production and SCFA increased substantially in groundnut hay based substrates, whereas gas production of BCS:Co substrates decreased and SCFA did not substantially change. In vitro digestibility was higher with rumen fluid from N?Dama whatever the diet of donor animals and the substrate incubated. GNH:Mo as donor diet also increased IVTD of all the substrates. Even though there was no clear response in vivo, this indicates a general stimulation of microbial activity in the rumen and renders moringa leaf meal a promising supplement. Averaged over all data there was a positive correlation (r2=0.53 p<0.001) between IVTD and in vivo OMD. This correlation was much stronger when calculated for a specific diet (e.g. r2=0.90 p<0.001 for BCS:Co, averaged over the breeds). Analyzing the data for the individual breeds affected correlations only to a minor degree. Thus, when testing a supplementation strategy in vitro, it should be important that donor animals are fed the same components (roughage and supplement) that will be combined at different levels in vitro, whilst the breed of donor animals may be of second importance. This work provides conclusive evidence that in vitro incubations may be used to design supplementation strategies, thus reducing the need for in vivo experiments. Moringa leaf meal is a promising local resource to substitute for conventional concentrate. Differences in productivity between breeds could be correlated to (and may be partially manifested through) a divergent community structure of rumen microbes. That, in turn, indicates that animals of different breeds might have a ?genetic background? that favours the establishment of a certain community, even if the animals are kept under identical conditions. This relationship should be investigated by more advanced molecular techniques.
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.
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.
Ruminal degradation characteristics of barley, rye, and triticale grains assayed in situ and in vitro, and by near-infrared spectroscopy
(2017) Krieg, Jochen; Rodehutscord, Markus
The milk yield of dairy cows and related energy and protein requirements have steadily increased in the last few decades. Since feed intake has not increased to the same extent as nutritional requirements, the concentration of nutrients in mixed rations had to be increased. An increase in energy concentration is often achieved by the inclusion of high levels of cereal grains. In the EU—apart from wheat—barley, rye, and triticale are widely cultivated cereal grains. Starch (ST), followed by crude protein (CP), is the main constituent of cereal grains. The rate and extent of ruminal CP and ST degradation can influence the performance and health of dairy cows, but data that can enable the comparison of ruminal degradation within and between barley, rye, and triticale grains are scarce. Commonly used techniques to explore ruminal degradation of feed are in situ and in vitro incubations. Both techniques require ruminal-fistulated animals, but alternative methods are being demanded by the community, in order to reduce the number of animal trials. An approach with the potential to estimate the nutritional value of various feeds is near-infrared spectroscopy (NIRS). The present thesis has two major parts. In the first part, ruminal degradation parameters and the effective degradability (ED) of DM, CP, and ST from barley, rye, and triticale grains are investigated using standardised in situ and in vitro incubation techniques. A total of 20 genotypes per grain species were used. In the second part, NIRS calibrations were developed with the aim of estimating the CP and ST concentrations of cereal grains and their incubation residues. Subsequently, data from in situ experiments were used to establish the calibrations for estimating the ruminal in situ degradation of cereal grains from their spectral data. In situ degradation studies have been conducted by ruminal incubation, utilising three lactating cows. Ruminal degradation parameters and ED (ruminal passage rate = 8%//h) were calculated. For in vitro incubations, the samples were incubated in a rumen fluid-buffer mixture (‘Hohenheim Gas Test’). The gas production was recorded for estimating gas production kinetics. In vitro gas production—in combination with crude nutrient concentrations—was used to estimate the metabolisable energy concentration (ME) and digestibility of organic matter (dOM). The degradation rates differed between and within the grain species for DM, CP, and ST. The variation within grain species was not reflected in the ED of CP and ST, due to the relatively fast and almost complete degradation of the grains. The ED of CP was 77% (69–80%) for barley, 85% (83–86%) for rye, and 82% (79–84%) for triticale. The corresponding ED of ST was 86% (82–88%), 95% (92–96%), and 94% (90–95%). Accordingly, the estimated ME (barley: 13.5 MJ/kg DM, rye: 13.9 MJ/kg DM, triticale: 13.5 MJ/ kg DM) showed only relatively minor variation within one grain species. The dOM was overall at a high level (barley: 91.3%, rye: 95.3%, triticale: 95.8%). The relatively small variation within one grain species could not be explained by the chemical and physical characteristics of the samples. Hence, it was concluded that it is feasible to use mean values for every species in feed formulation and ration planning. In the second part of this thesis, it was shown that it is possible to replace chemical CP and ST analyses of samples from in situ studies by NIRS without affecting the calculated ruminal degradation characteristics. NIRS could be used to estimate the ED of CP and ST from cereal grains. The sample set to establish the calibrations included barley, durum, maize, rye, triticale, and wheat grains. Calibrations for the CP and ST concentration were extended to pea samples. The calibrations with the best validation performance for CP and ST concentration were obtained by using the wavelength segment of 1250 to 2450 nm and the first derivative of the spectra (CP: R2 = 0.99; SEP = 0.46% DM. ST: R2 = 0.99; SEP = 2.10% DM). The results of in situ studies did not differ, irrespective of whether chemical or NIRS analysis was used. Like the CP and ST concentration, the ED was estimated with a high accuracy (ED8 CP: R2 = 0.95; SEP = 2.43%. ED8 ST: R2 = 0.97; SEP = 2.45%). However, calibrations need to be extended before they can be recommended for routine use. The present thesis demonstrates that the ED of CP and ST of barley, rye, and triticale grains differ between the species, but variation within one grain species is relatively small and not related to the chemical and physical characteristics of the grain. Hence, under the prevailing cultivation conditions, the mean values for each grain species in feed evaluation are deemed adequate. It was demonstrated that NIRS has the potential to facilitate the evaluation of the nutritive value of cereal grains for ruminants.
Untersuchungen zur Abundanz der Reblaus (Dactylosphaera vitifolii Shimer) und zur Nodositätenbildung in Abhängigkeit von Umweltfaktoren
(2000) Kopf, Andreas; Blaich, Rolf
The aim of the examinations was to investigate the abundance of Phylloxera (Dactylosphaera vitifolii Shimer), the occurrence of different biotypes of Phylloxera, the reaction of rootstocks to the infestation by Phylloxera and the influence of abiotic environmental conditions on the interaction between insect and plant. To investigate this interaction galls on rootlets (nodosities) and leaf galls were examined. The abundance of Phylloxera and the issue of the holocyclical reproduction in the wine region palatinate were evaluated in a field monitoring. In a special field trial the occurrence of different stages of Phylloxera and their damages on the rootstock were registered. With a dual aseptical in vitro system Phylloxera of different origins were examined on their aggressiveness to different varieties of rootstocks. In pot trials the influence of the type of soil and the effect of N-fertilization on the development of nodosities were investigated. The results of the examination show that Phylloxera can be found in nearly every part of the palatinate and that the improper cultivation of grafted rootstocks promotes the spreading of Phylloxera. Through shoots of rootstocks ? as they can be found in vineyards run wild - a holocyclical development of Phylloxera is made possible under appropriate climatical circumstances. Fitness, population dynamics of Phylloxera and the number of nodosities caused by the insects are correlating with their adaptation to a host rootstock. Pot studies have demonstrated that Phylloxera populations develop better in clay soil than sandy soil. High densities of Phylloxera in combination with a lack of N-supply increase a growth depression on grafted roots. It could also be proved that N-fertilization reduces the Phylloxera populations and the development of nodosities up to 98 %.
Variability of amino acid digestibility of cereal grains in laying hens
(2017) Zuber, Tobias; Rodehutscord, Markus
It was the objective of this doctoral thesis to generate a comprehensive data set of AA digestibility values of cereal grains in laying hens by using a strictly standardized assay procedure. Additionally, the suitability of two approaches to predict AA digestibility was examined. For this purpose, 80 genotypes of triticale, rye, corn, and wheat grains (n = 20 each) were grown as part of the “GrainUp” project. Apart from corn, the cereal species were grown under identical environmental conditions. The grain samples were comprehensively analyzed according to their physical properties, chemical composition, and gross energy concentration. The concentration of crude protein in the grain samples of triticale, rye, corn, and wheat was in the range of 113-138, 108-127, 78-112, and 125-162 g/kg dry matter, respectively. Additionally, the in vitro solubility of nitrogen (N) was determined in the grains after pretreatment with porcine pepsin and pancreatin. The animal trial comprised 16 Latin Squares (6x6), distributed among six subsequent runs. Thus, each run contained two to three Latin Squares. Cecectomized laying hens were individually housed in metabolism cages and fed either on a basal diet containing 500 g/kg cornstarch or one of the 80 cereal diets, with the cornstarch being replaced with a grain sample, for eight days. During the last four days, feed intake was recorded and excreta were collected quantitatively twice daily. After each collection period, the hens were group-housed in a floor pen for two days and offered a conventional layer diet. Amino acid digestibility of the grain samples was calculated using a linear regression approach. Relationships between AA digestibility and single analyzed fractions or the in vitro solubility of N of the cereal grains were examined by calculating Pearson product-moment correlation coefficients. Prediction equations to estimate AA digestibility were calculated by multiple regression analysis using a stepwise selection approach. Therefore, the variables were pooled according to their characteristics, and the prediction equations were calculated for the digestibility of each AA using each pool. The variables were offered in a linear or linear plus quadratic fashion and classified as significant predictors at P<0.10. The equations were assessed based on the adjusted R² and the root-mean-square error. The AA digestibility varied widely within and among the cereal species. The mean digestibility of lysine was 74% (digestibility range: 68-80%), 49% (35-59%), 79% (64-85%), and 80% (69-87%) for triticale, rye, corn, and wheat grains, respectively. A similar ranking was observed for methionine with a mean digestibility of 83% (digestibility range: 77-86%), 67% (57-75%), 91% (86-94%) and 84% (70-93%) for triticale, rye, corn, and wheat grains, respectively. Correlation analysis showed inconsistent results within and across the cereal species. Among the physical characteristics, significant correlations were detected for the thousand seed weight and the digestibility of a few AA in wheat, and for the test weight and the digestibility of a few AA in rye and corn. Significant correlations between NSP fractions and the digestibility of essential AA were detected only for rye grains. In this crop, the concentration of arabinoxylans and total NSP in the grains was negatively correlated with the digestibility of arginine, leucine, phenylalanine, and threonine. The concentration of crude protein in corn grains was positively correlated with the digestibility of essential AA, except isoleucine, tryptophan, and valine. In contrast, only a few significant positive correlations between crude protein concentration and essential AA digestibility were found for triticale and rye grains. No significant correlations were found for wheat grains in this regard. The in vitro solubility of N was negatively and positively correlated with the digestibility of a few AA in triticale and rye grains, respectively. The accuracy of the predictive equations was generally low (adjusted R² below 0.7 in most cases), and varied considerably between both pools of variables for the same AA and the same pool of variables for different AA. Thus, single or several physical or chemical characteristics could not explain the variation in AA digestibility in laying hens and the development of prediction equations sufficiently precise for the practical application was not possible.