Linkage of in situ ruminal degradation of crude protein with ruminal degradation of amino acids and phytate from different soybean meals in dairy cows.

The objectives of this study were to determine the range in ruminal degradability of crude protein (CP) and intestinal digestibility of rumen undegradable protein in commercial soybean meal (SBM) and to investigate the range in in situ ruminal AA and phytate (InsP6) degradation and their relationship to CP degradation. An in situ study was conducted using 3 lactating Jersey cows with permanent rumen cannulas. Seventeen SBM variants from Europe, Brazil, Argentina, North America, and India were tested for ruminal CP and AA degradation, and in vitro intestinal digestibility of rumen undegradable protein. Nine variants were used to investigate the ruminal degradation of InsP6. The estimated rapidly degradable fraction (a) of CP showed an average value of 4.5% (range: 0.0%-9.0%), the slowly degradable fraction (b) averaged 95% (91%-100%), and the potential degradation was complete for all 17 SBM variants. The degradation of fraction b started after a mean lag phase of 1.7 h (1.1-2.0 h) at an average rate (c) of 10% per hour, but with a high range from 4.5% to 14% per hour. Differences in the degradation parameters induced a considerable range in CP effective degradation at a rumen passage rate of 6% per hour (CPED6) from 38% to 67%; hence, the concentration of rumen undegradable protein varied widely from 33% to 62%. The range in AA degradation between the SBM variants was high, with Ser showing the widest range, from 28% to 96%, and similar for the other AA. The regression equations showed close relationships between CP and AA degradation after 16 h of in situ incubation. However, the slopes of the linear regressions were significantly different between AA, suggesting that degradation among individual AA differs upon a change in CP degradation. The concentrations of InsP6 and myo-inositol pentakisphosphate in bag residues in the in situ study decreased constantly with longer ruminal incubation times. The ruminal degradation parameters of InsP6 ranged from 11% to 37% for fraction a, 63% to 89% for fraction b, and from 7.7% to 21% per hour for degradation rate c, with average values of 21%, 79%, and 16% per hour, respectively. The calculated InsP6 effective degradation at a rumen passage rate of 6% per hour (InsP6ED6) varied from 61% to 84% among the SBM variants. Significant correlations were detected between InsP6ED6 and CPED6 and between InsP6ED6 and chemical protein fractions A, B1, B2, B3, and C. Linear regression equations were developed to predict ruminal InsP6 degradation using CPED6 and chemical protein fractions B3 and C chosen by a stepwise selection procedure. We concluded that a high range in CP, AA, and InsP6 degradation exists among commercial SBM, suggesting that general degradability values may not be precise enough for diet formulation for dairy cows. Degradation of CP in SBM may be used to predict rumen degradation of AA and InsP6 using linear regression equations. Degradation of CP and InsP6 could also be predicted from the chemical protein fractions.

Investigation on adaptations of broiler chickens to high dietary free amino acid levels in nitrogen utilisation and plasma amino acid concentrations.

1. A reduction in crude protein (CP) in feed for broiler chickens necessitates elevated free amino acid (AA) levels to meet the requirement of each AA. This study investigated adaptations following a change to diets with increasing free AA concentrations and possible reasons for the limitation caused by the inclusion of more free AA.2. Male Ross 308 broiler hatchlings received a starter diet (164 g CP/kg containing 80 g/kg soy protein isolate (SPI)) until d 7. From d 7-22, birds received a diet almost identical to the starter diet or two other diets, where 50% or 100% of digestible AA in SPI were substituted with a free AA mixture. Birds were allocated to metabolism units located in the same barn to determine performance (n = 7 units) and blood traits (n = 14 birds). Total excreta collection was performed on d 7-8, 8-9, 9-10, 11-12, 14-15 and 21-22. Blood samples were collected on d 7, 8, 9, 11, 14 and 21.3. Average daily weight gain (ADG) and average daily feed intake (ADFI) was unaffected at 50% AA substitution but decreased at 100% AA substitution on d 7-22 (p ≤ 0.001). The 100% substitution led to a decline in ADG and ADFI consistently on all days (p ≤ 0.037) except on d 11-12. A 50% AA substitution resulted in lower ADFI on d 7-8 and 14-15 (p ≤ 0.032). Nitrogen utilisation efficiency (NUE) was on a level of ~ 0.74 and was only affected by treatment up to d 11-12 (p ≤ 0.008). Concentrations of 10, 9, 8, 10 and 4 plasma free AA were affected on d 8, 9, 11, 14 and 21, respectively (p ≤ 0.037).4. Following a change to diets containing high levels of free AA, NUE and free AA concentrations in the circulation became more balanced within 3 to 7 d. The results suggested that peptide-bound and free AA did not cause different NUE, particularly 3 and 7 d after the diet change.

Bone characteristics, pre-caecal phytate degradation, mineral digestibility and tissue expression were marginally affected by zinc level and source in phytase-supplemented diets in 21-day-old broiler chickens.

1. This study determined the effect of dietary Zn concentration and source in phytase-supplemented diets on bone mineralisation, gastrointestinal phytate breakdown, mRNA-level gene expression (in jejunum, liver and Pectoralis major muscle) and growth performance in broiler chickens.2. Male Cobb 500 broilers were housed in floor pens (d 0-d 21) to test seven treatments with six replicate pens (12 birds per pen). Diets were arranged in a 2 × 3 + 1-factorial arrangement. The experimental factors were Zn source (Zn-oxide (ZnO) or Zn-glycinate (ZnGly) and Zn supplementation level (10, 30 or 50 mg/kg of diet). A maize-soybean meal-based diet without supplementation and formulated to contain 28 mg Zn/kg (analysed to be 35 mg Zn/kg), served as a control.3. Zinc source and level did not influence (p > 0.05) bone ash concentration and quantity or mineral concentrations in bone ash. Tibia thickness was greater in the treatment ZnO10 than in the treatments ZnO30 and ZnGly50 (Zn level × Zn source: p = 0.036), but width and breaking strength were not affected.4. Pre-caecal P digestibility and concentrations of phytate breakdown products in the ileum, except for InsP5, were not affected by Zn source or level. Only the expression of EIF4EBP1 (eukaryotic translation initiation factor 4E-binding protein 1) and FBXO32 (F-box only protein 32) in Pectoralis major muscle was affected by source, where expression was increased in ZnO compared to ZnGly diets (p < 0.05).5. In conclusion, Zn level and source did not affect gastrointestinal phytate degradation and bone mineralisation in phytase-supplemented diets. The intrinsic Zn concentration appeared to be sufficient for maximum bone Zn deposition under the conditions of the present study but requires validation in longer-term trials.

Effects of feed particle size, calcium concentration and phytase supplementation on InsP6 degradation in broiler chickens fed pelleted diets.

1. The objective of the trial was to study the single and interactive effects of feed particle size in pelleted feed, dietary calcium (Ca) concentration and microbial phytase supplementation in broiler chickens. The studied traits were myo-inositol (1,2,3,4,5,6) hexakis (dihydrogen phosphate) (InsP6) degradation, pre-caecal digestibility of phosphorus (P), Ca and amino acids (AA) and retention of P, Ca and nitrogen (N).2. Male Ross 308 broiler chickens were housed in metabolism units in groups of 10 and allocated to one of eight diets with seven pen replicates per diet. The 2 × 2 × 2-factorial arrangement included coarse and fine feed particle size (309 or 222 µm), low and high Ca concentration (4.9 and 7.2 g/kg) and without or with phytase supplementation (1,000 FTU/kg).3. Pre-caecal InsP6 disappearance was higher with coarse than fine feed particle size when no phytase was added (54 vs. 48%) but not when phytase was added (74%; p = 0.046). High dietary Ca feeds decreased pre-caecal InsP6 disappearance (67 to 59%) and P digestibility (65 to 55%; p < 0.001). Gizzard pH was lower with coarse than fine feed particle size and higher with high Ca than low Ca (p < 0.001). Pre-caecal digestibility of most AA was approximately 3.5%-points lower with high Ca without phytase compared to the other treatments (p ≤ 0.047). Coarse feed particle size caused higher pre-caecal AA digestibility than fine particle size (~2%-points; p ≤ 0.031). InsP6 disappearance in the crop increased at high Ca concentration when phytase was added (22 vs. 37%; p = 0.011).4. Coarser feed particle size in pellets increased gastrointestinal InsP6 degradation and nutrient digestibility, likely owing to effects on the gizzard functions. Additional Ca supply exerted antinutritive effects that was not compensated for by using coarser feed particles.

Phytate degradation and phosphorus utilisation by broiler chickens fed diets containing wheat with increased phytase activity.

1. The objective of this study was to investigate wheat genotypes bred for increased intrinsic phytase activity for InsP6 disappearance and the formation of lower inositol phosphates in such wheat-fed broiler chickens. The influence of monocalcium phosphate (MCP) supplementation on these characteristics and the utilisation of P and Ca were also determined. A three-step in vitro assay and a broiler trial were performed.2. In the 63 wheat genotypes tested in vitro, phytase activity varied from 1900 FTU/kg to 5200 FTU/kg, and InsP6 disappearance increased with higher phytase activity of wheat in a linear manner. The addition of MCP significantly reduced in vitro InsP6 disappearance by one-third, independent of the inclusion level of wheat in the feed. When exogenous phytase was added to wheat, in vitro InsP6 disappearance increased independently of the phytase activity of the wheat used.3. In the broiler trial, four wheat genotypes with phytase activities between 2400 and 3700 FTU/kg were included at 400 g/kg in diets with and without MCP. The diets were not pelleted. Separately, wheat 1, without MCP, was tested with the addition of exogenous phytase. Unsexed Ross 308 broiler chickens were allocated to 72 metabolic units of 10 birds each and assigned one of the nine diets. Mineral utilisation was measured based on excreta collection from 20 to 23 d of age. Digesta from the crop and terminal ileum were collected on d 24.4. In the crop and ileum, InsP6 disappearance was not affected by the wheat genotypes, but the addition of MCP significantly decreased InsP6 disappearance. Precaecal P disappearance was significantly reduced by the addition of MCP, with wheat genotypes also exerting an effect. Wheat genotypes and the addition of exogenous phytase significantly affected P utilisation. Exogenous phytase had no effect on InsP6 disappearance in the crop but did up to the terminal ileum, the precaecal InsP6 and P disappearance increased with the addition of exogenous phytase.5. Although the intrinsic wheat phytase activity exerted distinct effects on in vitro InsP6 disappearance, no such effect was found in the broiler trial. The addition of MCP significantly inhibited InsP6 degradation in vitro and in vivo.

Mapping genes for phosphorus utilization and correlated traits using a 4k SNP linkage map in Japanese quail (Coturnix japonica).

A large F2 cross with 920 Japanese quail was used to map QTL for phosphorus utilization, calcium utilization, feed per gain and body weight gain. In addition, four bone ash traits were included, because it is known that they are genetically correlated with the focal trait of phosphorus utilization. Trait recording was done at the juvenile stage of the birds. The individuals were genotyped genome-wide for about 4k SNPs and a linkage map constructed, which agreed well with the reference genome. QTL linkage mapping was performed using multimarker regression analysis in a line cross model. Single marker association mapping was done within the mapped QTL regions. The results revealed several genome-wide significant QTL. For the focal trait phosphorus utilization, a QTL on chromosome CJA3 could be detected by linkage mapping, which was substantiated by the results of the SNP association mapping. Four candidate genes were identified for this QTL, which should be investigated in future functional studies. Some overlap of QTL regions for different traits was detected, which is in agreement with the corresponding genetic correlations. It seems that all traits investigated are polygenic in nature with some significant QTL and probably many other small-effect QTL that were not detectable in this study.

The relevance of glycine and serine in poultry nutrition: a review.

1. Dietary glycine equivalents (Glyequi) for glycine and serine represent the first-limiting non-essential amino acid in poultry diets. Targeted adjustment of essential amino acids and Glyequi in diets can considerably decrease crude protein (CP) in poultry diets below the limit of CP reduction when only essential amino acids are adjusted. 2. The level to which CP can be reduced in diets adequate in Glyequi depends on the objective; which includes reducing dietary CP without affecting performance and increasing nitrogen utilisation efficiency. Dietary CP can be reduced to ~15-16% in diets for up to 21 d old broiler chicken without affecting growth performance compared to responses to diets with currently common CP concentrations by considering Glyequi in the diet formulation. Dietary CP can be further reduced to maximise nitrogen utilisation efficiency; however, this leads to reduced growth performance. 3. The dietary Glyequi requirement of poultry varies depending on other dietary constituents. In broiler chickens up to 21 days of age, the dietary Glyequi requirement is estimated to be between 11 and 20 g/kg. This estimate is influenced by the concentrations of Cys and the endogenous Glyequi precursors, threonine and choline. Urinary nitrogen excretion seems to be a major determinant of the response to dietary Glyequi, because it is needed for uric acid formation. 4. The variable requirement for dietary Glyequi means that its static recommendation in poultry diets would lead to high safety margins in Glyequi supply or the risk of Glyequi deficiency. Variable recommendations for dietary Glyequi concentrations would help to supply birds based on their specific requirements and could reduce nitrogen emissions originating from poultry farming.

Variability of amino acid digestibility of lupin and pea grains in caecectomised laying hens.

1. The objective of this study was to investigate the variations in amino acid (AA) digestibility of lupin and pea grains in caecectomised laying hens. The relationship between AA digestibility and chemical constituents of the grains was determined. 2. Twelve variants of lupins and peas were each added to a basal diet at a concentration of 300 g/kg, at the expense of maize starch. The lupin and pea variants were separately investigated in two subsequent trials. Each trial consisted of two 7 × 7 Latin squares, each comprising the basal diet and six diets with lupins or peas. 3. Fourteen caecectomised laying hens (LSL-classic) were individually housed in metabolism cages and 120 g/d of experimental diets were provided for eight days. During the last four days, excreta were collected quantitatively and feed intake was recorded. A regression approach was used to determine the AA digestibility of the lupin and pea variants. 4. Amino acid digestibility of the lupins and peas was high, although significant differences in AA digestibility among the lupins and peas were detected. The digestibility of lysine was in the range of 0.87-0.91 and 0.87-0.93 for lupins and peas, respectively. The digestibility of methionine in lupins and peas varied between 0.80-0.88 and 0.72-0.90. Variations in AA digestibility in peas were more pronounced than in lupins. 5. Significant correlations between chemical constituents of lupins, such as alkaloids, and AA digestibility were detected in some cases, without a consistent pattern. In peas, tannin concentration and the insoluble protein fraction were negatively correlated with digestibility of some AAs, but only when one colour flower variant was considered. Trypsin inhibitor activity in peas was negatively correlated with AA digestibility, particularly for the white flower variants.

Effect of the ionophore monensin and tannin extracts supplemented to grass silage on populations of ruminal cellulolytics and methanogens in vitro.

This study examined whether the methane-decreasing effect of monensin (∼21%) and different hydrolysable tannins (24%-65%) during in vitro fermentation of grass silage was accompanied by changes in abundances of cellulolytics and methanogens. Samples of liquid (LAM) and solid (SAM) associated microbes were obtained from two rumen simulation technique experiments in which grass silage was either tested in combination with monensin (0, 2 or 4 mg d-1) or with different tannin extracts from chestnut, valonea, sumac and grape seed (0 or 1.5 g d-1). Total prokaryotes were quantified by 4',6-diamidino-2-phenylindol (DAPI) staining of paraformaldehyde-ethanol-fixed cells and relative abundances of ruminal cellulolytic and methanogenic species were assessed by real time quantitative PCR. Results revealed no change in absolute numbers of prokaryotic cells with monensin treatment, neither in LAM nor in SAM. By contrast, supplementation of chestnut and grape seed tannins decreased total prokaryotic counts compared to control. However, relative abundances of total methanogens did not differ between tannin treatments. Thus, the decreased methane production by 65% and 24% observed for chestnut and grape seed tannins, respectively, may have been caused by a lower total number of methanogens, but methane production seemed to be also dependent on changes in the microbial community composition. While the relative abundance of F. succinogenes decreased with monensin addition, chestnut and valonea tannins inhibited R. albus. Moreover, a decline in relative abundances of Methanobrevibacter sp., especially M. ruminantium, and Methanosphaera stadtmanae was shown with supplementation of monensin or chestnut tannins. Proportions of Methanomicrobium mobile were decreased by monensin in LAM while chestnut and valonea had an increasing effect on this methanogenic species. Our results demonstrate a different impact of monensin and tannins on ruminal cellulolytics and gave indication that methane decrease by monensin and chestnut tannins was associated with decreased abundances of M. ruminantium and M. stadtmanae.

Effect of particle size distribution of maize and soybean meal on the precaecal amino acid digestibility in broiler chickens.

1. Herein, it was investigated whether different particle size distributions of feed ingredients achieved by grinding through a 2- or 3-mm grid would have an effect on precaecal (pc) amino acid (AA) digestibility. Maize and soybean meal were used as the test ingredients. 2. Maize and soybean meal was ground with grid sizes of 2 or 3 mm. Nine diets were prepared. The basal diet contained 500 g/kg of maize starch. The other experimental diets contained maize or soybean meal samples at concentrations of 250 and 500, and 150 and 300 g/kg, respectively, instead of maize starch. Each diet was tested using 6 replicate groups of 10 birds each. The regression approach was applied to calculate the pc AA digestibility of the test ingredients. 3. The reduction of the grid size from 3 to 2 mm reduced the average particle size of both maize and soybean meal, mainly by reducing the proportion of coarse particles. Reducing the grid size significantly (P < 0.050) increased the pc digestibility of all AA in the soybean meal. In maize, reducing the grid size decreased the pc digestibility of all AA numerically, but not significantly (P > 0.050). The mean numerical differences in pc AA digestibility between the grid sizes were 0.045 and 0.055 in maize and soybean meal, respectively. 4. Future studies investigating the pc AA digestibility should specify the particle size distribution and should investigate the test ingredients ground similarly for practical applications.

In situ and in vitro evaluation of crude protein degradation and utilisable crude protein content of barley, rye and triticale grains for ruminants.

Rations for dairy cows are comprised of high proportions of cereal grains. Thus, despite their low crude protein (CP) content, grains can contribute considerably to the CP intake of dairy cows. This study was conducted to describe and compare ruminal CP degradation of a broad range of barley, rye and triticale genotypes in situ and in vitro and different methods to estimate the utilisable CP at the duodenum (uCP). Twenty samples each of rye, barley and triticale were incubated in situ and in vitro. Exponential regression analyses were used to estimate in situ degradation parameters. Further, the effective degradability (ED), ruminal undegraded CP (UDP) and uCP for ruminal passage rates of 5% and 8% per hr were estimated. The uCP was estimated in vitro and based on two different approaches using in situ UDP data and estimates of microbial synthesised protein (based on fermented organic matter [fOM] or equations of the Gesellschaft für Ernährungsphysiologie). The degradation rate declined from rye (43% per hr) to triticale (27% per hr) to barley (20% per hr), and it exhibited remarkable variation between the genotypes of a single species. The maximal degradable CP fraction also differed between the species, but was overall very high (94%-99%). The lowest washout fraction (26%) and the highest variation in ED (77%-86% and 69%-80% for a passage rate of 5% and 8% per hr, respectively) were found in barley. The in situ uCP content (estimated using fOM) was lower for barley than for rye and triticale at ruminal passage rates of 5% and 8% per hr (barley: 157 g/kg DM at both passage rates; rye and triticale: 168 (at 5% per hr) and 169 (at 8% per hr) g/kg DM). In vitro estimations of uCP did not differ between the grain species and uCP estimated according to GfE was higher for triticale than for barley and rye, which did not differ. The low variation within a single grain species and the weak correlations between ruminal CP degradation and nutrient concentrations suggested that differentiation of ED and uCP between the genotypes of a single grain species is not necessary.

Effect of dietary mineral phosphorus and phytate on in situ ruminal phytate disappearance from different concentrates in dairy cows.

The first objective of this study was to determine the influence of dietary composition on the in situ disappearance of phytate (InsP6) from wheat, corn, soybean meal, and rapeseed meal [solvent-extracted, without (RSM) or with (hRSM) heat treatment] in the rumen of dairy cows. The second objective was to assess the primary degradation products of InsP6 in the rumen. Three diets differing in phosphorus and InsP6 concentration (basal diet = 0.38% P in dry matter; high-P diet = 0.56% P; high-InsP6 diet = 0.39% P) were fed to 3 ruminally fistulated lactating Jersey cows in a 3 × 3 Latin square. Ground concentrates (sieve size = 2 mm) were incubated in polyester bags in the rumen for 2, 4, 8, 16, and 24 h. The bag residues were analyzed for P, InsP6, isomers of lower inositol phosphates (InsP5, InsP4, InsP3), and crude protein. The InsP6 disappeared more rapidly from cereal grains than from oilseed meals; however, after 24 h of incubation ≥95% InsP6 had disappeared from all concentrates except hRSM (57%; diet average). Feeding the high-InsP6 diet increased InsP6 disappearance for oilseed meals, but not for corn and wheat. The predominant InsP5 isomer in all bag residues was Ins(1,2,4,5,6)P5 followed by Ins(1,2,3,4,5)P5 and Ins(1,2,3,4,6)P5. A further InsP5 isomer [Ins(1,3,4,5,6)P5] was detected in both rapeseed meal bag residues. Feeding the high-InsP6 diet led to lower concentrations of Ins(1,2,4,5,6)P5 and Ins(1,2,3,4,5)P5, whereas an interaction between diet, concentrate, and time occurred for Ins(1,2,3,4,6)P5 and Ins(1,3,4,5,6)P5. The results confirm the high potential of rumen microorganisms to hydrolyze InsP6; however, increasing the amount of InsP6 in the diet can further enhance InsP6 hydrolysis, which may be relevant when concentrates with slowly degradable InsP6, such as RSM or heat-treated concentrates, are fed to dairy cows. Based on the concentrations of InsP5 isomers, 3 and 6 phytases appear to play a major role in the rumen. Conversely, intrinsic plant phytase activity appears to be less relevant as the percentage of its primary hydrolysis product, Ins(1,2,3,4,5)P5, changed only slightly upon using wheat known for high intrinsic phytase activity instead of the other concentrates. Additional information regarding the factors influencing the extent of ruminal InsP6 disappearance will require further studies to determine the phytase activity of rumen microorganisms and the characteristics of their respective phytases.

In situ starch and crude protein degradation in the rumen and in vitro gas production kinetics of wheat genotypes.

The objective of this study was to determine the variation of in situ ruminal degradation characteristics of dry matter (DM), crude protein (CP) and starch (ST), and to determine the effective degradation (ED) of wheat genotypes. Further, multivariate associations of these in situ values with their corresponding in vitro gas production (GP) kinetics and laboratory measurements were evaluated using correlation and multiple linear regression analyses. Grains of 20 genotypes of wheat were characterized by proximate constituents, amino acid (AA) composition and physical characteristics. Ruminal degradation kinetics were determined by in situ degradation of DM, CP and ST, and subsequent evaluation of in vitro GP relative to time courses. In situ and GP measurements were fitted to an exponential equation, and ED was calculated using passage rates in the rumen of 5%/h (ED5) and 8%/h (ED8). To predict ED8 of CP (EDCP8) and ST (EDST8), correlations were evaluated and stepwise multiple linear regression analyses were applied. Estimated degradation parameters varied considerably between wheat genotypes irrespective of the nutrient tested. Variance in a, b and c was not reflected in the variation of the ED, due to high degradation rates (c). The assumed passage rate also impacted estimation of the ED minimally. Estimated GP parameters varied only slightly among wheat genotypes. Nevertheless, regression models explained up to 80 and 99% of the variance in EDCP8 and EDST8, respectively, and associations between EDST8 and EDCP8 and chemical and physical characteristics of grains were detected. As ST is the primary nutrient in wheat grains and can comprise substantial portions of dairy rations, the total amount of ST as well as its ED in the rumen should be taken into account when wheat is incorporated into dairy rations. Conversely, variance in wheat grain CP degradation was very low and can largely be neglected in practical ration formulation for ruminants.

Ruminal phytate degradation of maize grain and rapeseed meal in vitro and as affected by phytate content in donor animal diets and inorganic phosphorus in the buffer.

The ruminal disappearance of phytate phosphorus (InsP6 -P) from maize grain and rapeseed meal (RSM) was determined in two in vitro studies. In experiment 1, two diets differing in phosphorus (P) and InsP6 -P concentration were fed to the donor animals of rumen fluid (diet HP: 0.49% P in dry matter, diet LP: 0.29% P). Maize grain and RSM were incubated in a rumen fluid/saliva mixture for 3, 6, 12 and 24 h. In experiment 2, a diet similar to diet HP was fed, and the rumen fluid was mixed with artificial saliva containing 120 mg inorganic P/l (Pi) or no inorganic P (P0). Maize grain and RSM were incubated with either buffer for 3, 6, 12 and 24 h. Total P (tP) and InsP6 concentration were analysed in the fermenter fluids and feed residues. The disappearance of InsP6 -P from maize was completed after 12 h of incubation in both experiments. From RSM, 93% (diet LP) and 99% (diet HP) of the InsP6 -P in experiment 1 and 80% (Pi) and 89% (P0) in experiment 2 had disappeared after 24 h of incubation. InsP6 -P disappearance was higher when diet HP was fed (maize: 3 and 6 h; RSM: 6 and 24 h of incubation) and when rumen fluid was mixed with buffer P0 (maize: 6 h; RSM: 12 and 24 h of incubation). InsP6 -P concentration in the fermenter fluids was higher for maize, but no accumulation of InsP6 -P occurred, indicating a prompt degradation of soluble InsP6 . These results confirmed the capability of rumen micro-organisms to efficiently degrade InsP6 . However, differences between the feedstuffs and diet composition as well as the presence of inorganic P in the in vitro system influenced the degradation process. Further studies are required to understand how these factors affect InsP6 degradation and their respective relevance in vivo.

Inferring relationships between Phosphorus utilization, feed per gain, and bodyweight gain in an F2 cross of Japanese quail using recursive models.

Phosphorus utilization (PU) has received considerable attention in poultry nutrition. However, reliable estimates of genetic parameters for PU and related traits have largely not been reported until now; however, these are needed to assess whether selection for an improved PU would result in selection response. A large Japanese quail F2 cross was generated and 888 F2 individuals were phenotyped for PU, bodyweight gain (BWG), and feed per gain (F:G). Because it can reasonably be assumed that the interrelationships between these traits are complex, structural equation models were used. The structural coefficient λij describes the rate of change of trait I with respect to trait j for a model with a recursive effect of trait j on trait i Three recursive structural coefficients (λF:G,PU,λBWG,PU,λBWG,F:G) were selected a priori based on biological knowledge. The model was fitted using ASReml software. Standard errors of estimated variance components and genetic parameters were approximated using the delta method. The heritability of PU, F:G, and BWG were 0.136, 0.118, and 0.092. The structural coefficient[Formula: see text]indicates that an increase in PU leads to reduced and thus improved F:G. The estimate[Formula: see text]indicates that improved F:G leads to an increase in BWG. The overall effect of PU on BWG was[Formula: see text]i.e. an increase in PU of 1% leads to an increase of BWG of 0.374 g in the data collection period, which spanned five days. The phenotypic and genetic correlations were negative between PU and F:G as well as between BWG and F:G and were positive between PU and BWG. These correlations are driven by direct genetic effects (pleiotropic genes or genes being in linkage disequilibrium) as well as by indirect genetic effects (genes affecting trait j affected indirectly trait i). The application of structural equation models contributed to our understanding of the complex biological relationship between PU, F:G, and BWG in quails. PU shows a heritability that is sufficient to achieve a selection response when breeding for this very-hard-to-measure trait.

Effect of glycine supplementation in low protein diets with amino acids from soy protein isolate or free amino acids on broiler growth and nitrogen utilisation.

Here, it was investigated whether substitution of amino acids (AA) from soy protein isolate with free AA in low crude protein diets influences the growth performance and N utilisation in broilers, and whether interactions with dietary glycine equivalent (Glyequi) concentration exist. Birds were distributed in two 2 × 2 factorial arrangements of 48 floor pens containing 10 birds each, plus 48 metabolism cages containing two birds each. Experimental feed was provided for ad libitum consumption from d 7 to 22. Diets contained either a soy protein isolate at 79 g/kg or a mix of free AA, which supplied the same amount of 18 proteinogenic AA. A mix of free glycine and l-serine was used to obtain low and high (12.0 and 20.5 g/kg dry matter) levels of dietary Glyequi. Substitution of soy protein isolate with free AA reduced the average daily gain and feed efficiency, mainly due to reduced feed intake. Efficiency of N accretion was not influenced by the AA source or Glyequi concentration on d 21, possibly due to the lower AA digestibility of soy protein isolate and higher urinary excretion of nitrogenous substances in the treatments with the AA mix. The average daily weight gain of the treatments with high Glyequi concentration was higher for both AA sources. This increase was due to higher average daily feed intake by broilers in the treatments with soy protein isolate and due to the increased feed efficiency in the treatments with the AA mix. Broilers exhibited different growth responses to dietary Glyequi between the AA sources; however, these responses could not be attributed to the different utilisation of Glyequi for uric acid synthesis.

Effect of donor animal species and their feeding on the composition of the microbial community establishing in a rumen simulation.

AIMS: To investigate the effect of donor animal species and their feeding on the composition of the active fraction of rumen microbiota established during in vitro experiments with different forages. METHODS AND RESULTS: Rumen simulation experiments were conducted with maize silage (MS) and grass silage (GS) as substrates. Four experimental runs were performed with ruminal contents of sheep and cows fed either with hay and concentrate or with MS or GS, respectively. Liquid- and solid-associated microbes (LAM and SAM) were fixed for fluorescence in situ hybridization after 14 days of incubation. The LAM were characterized by higher proportions of Lachnospiraceae, Bacteroidetes, Deltaproteobacteria and Methanobacteriaceae at hay-concentrate-based feeding of the donor animals whereas counts of Gammaproteobacteria were lower. Similar results were found for SAM. Hay-concentrate-based feeding caused a higher ratio of Bacteria:Archaea in SAM. Incubations with GS seemed to enhance Bacteroidetes, Deltaproteobacteria and Archaea whereas numbers of Gammaproteobacteria were enhanced in MS experiments. The effect of the donor animal species was limited to the number of Archaea establishing in vitro being higher for sheep than for cows. CONCLUSIONS: The feeding of donor animals, more than the animal species itself, affects the composition of the ruminal microbial community that establishes in vitro. SIGNIFICANCE AND IMPACT OF THE STUDY: Data suggest the need of a standardized approach for studying the rumen microbiota in a rumen simulation. Moreover, this study provides fundamental data on the composition of the ruminal microbial community when different diets are fed to donor animals.

Meta-analysis of the influence of dietary glycine and serine, with consideration of methionine and cysteine, on growth and feed conversion of broilers.

The existing literature is inconsistent with respect to optimal dietary concentrations of glycine (Gly) and serine (Ser) in broiler feed. Therefore, we conducted a meta-analysis to investigate the response of broilers to dietary levels of Gly using a full quadratic model based on mixed model methodology. Response was measured as ADG (g/d), ADFI (g/d), and G:F (g/g). In addition, the influence of other dietary constituents was evaluated. This meta-analysis was based on a data set comprising a total of 9,626 broilers in 10 peer-reviewed papers that investigated the response of broilers to different dietary concentrations of Gly, achieved by addition of free Gly. The fitted quadratic model, with either Gly+Ser or the calculated glycine equivalent (Glyequi) of both amino acids as the independent variable, revealed that all model terms were significant (P ≤ 0.05), and hence proved a curvilinear relationship between these independent variables and response traits. The R(2) value and root MS error confirmed a strong relationship between observed and predicted traits. A comparison of the influence of Gly+Ser and Glyequi on response traits revealed that both approaches produced similar results. Because Glyequi should meet the physiological values of a diet better than Gly+Ser, models with 2 independent variables were conducted using Glyequi. The second independent variables were methionine (Met):TSAA ratio and the concentrations of cysteine (Cys) and CP. In models with one or 2 independent variables, the impact of dietary Gly on ADFI was low. By contrast, G:F was markedly influenced by dietary Gly; this effect intensified at lower Met:TSAA ratios and higher Cys and CP levels. ADG was also a function of Glyequi and the second independent variables. For ADG, an optimal Met:TSAA ratio of 0.655 and Cys concentration of 0.302% was calculated. Following the nonlinear nature of relationship, generally applicable replacement values could not be calculated. However, it was concluded that consideration of dietary Cys can diminish the requirement for Glyequi, and therefore, enable a reduction in the CP of broiler diets without limiting growth performance.

A quantitative study of the interactive effects of glycine and serine with threonine and choline on growth performance in broilers.

Differences in the optimal dietary concentrations of Gly (glycine) and Ser (serine) in broiler diets may be due to levels of endogenous Gly precursors that differ in literature. Therefore, we measured the extent of the interactive effects between equivalents of Gly and Ser (Glyequi) and the endogenous Gly precursors choline and Thr (threonine) on growth performance. A fractional central composite design included concentrations of 15-25 g/kg DM, 0.6-2.0 g/kg DM, and 6.4-10.4 g/kg DM for Glyequi, choline, and Thr, respectively, in 5 levels each. The various concentrations were achieved by adding Gly, choline chloride, and l-Thr to a basal mix. Except for 20 replicates of the central diet, all treatments were tested with 5 replicates, each with 10 birds. Food was provided for ad libitum consumption throughout the experiment. The data were evaluated using artificial neural networks. Digestibility was studied for selected diets using separate birds. Since average daily feed intake (ADFI) varied between replicates, the intake of prececal digestible Glyequi, choline, and prececal digestible Thr were more adequate independent variables than the dietary concentration of each amino acid. From d 1 to d 7, no treatment effects on G:F and average daily gain (ADG) were detected; subsequent results refer to the period from d 7 to d 21. Increasing prececal digestible Thr intake considerably decreased the need for prececal digestible Glyequi to achieve certain levels of G:F and ADG. The extent of this effect cannot be explained only by the endogenous metabolism of Thr to Gly. Since essential amino acids were present above the recommended levels, Thr probably limited performance, and excessive intake of other essential amino acids prompted a Gly-dissipating process. Choline exerted a considerable effect on the required intake of prececal digestible Glyequi and prececal digestible Thr to achieve certain levels of G:F and ADG. The results of this study partly explain the previously reported variations in response to dietary Thr, Gly, and Ser.

A pilot study of the genetic variation of phosphorus utilization in young Japanese quail (Coturnix japonica).

This study estimated the genetic variance components of P utilization in Japanese quail. A parental generation was assembled from an unselected random-bred Japanese fattening quail line. Seven sires and 14 dams were randomly selected, and each sire was paired with 2 dams to produce full and half sibs. A total of 200 unsexed 1-d-old quail with known pedigree were wing-banded and raised during the first 4 d posthatch in groups in floor pens on wood shavings and fed a preexperimental diet that was adequate in all nutrients. Starting on d 5, quail were individually housed in metabolic compartments on P-free filter paper. This started a balance trial with 5 d of adaption and 5 d of total excreta collection. During this balance period, all quail were fed a low-P (3.9 g/kg of DM) corn-soybean meal-based diet with a Ca:P ratio of 1.6:1.0. Phosphorus and Ca utilization were determined individually using the difference in P or Ca intake and the total P or Ca excretion. The average P utilization was 72% and the average Ca utilization was 63%, each with very high variation. Heritabilities were estimated to be 0.09 (SE = 0.09) for P utilization and 0.09 (SE = 0.09) for Ca utilization. Heritabilities were close to the values reported in the literature for broilers and suggest that quail are suitable as a model animal. The SE of the heritability estimates were large. This implies that further studies with a larger sample size are needed to identify genetic and physiological mechanisms that influence P and Ca utilization in Japanese quail.