1. Dietary glycine equivalents (Gly
equi
) for glycine and serine represent the first-limiting non-essential amino acid in poultry diets. Targeted adjustment of essential amino acids and Gly
equi
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 Gly
equi
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 Gly
equi
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 Gly
equi
requirement of poultry varies depending on other dietary constituents. In broiler chickens up to 21 days of age, the dietary Gly
equi
requirement is estimated to be between 11 and 20 g/kg. This estimate is influenced by the concentrations of Cys and the endogenous Gly
equi
precursors, threonine and choline. Urinary nitrogen excretion seems to be a major determinant of the response to dietary Gly
equi
, because it is needed for uric acid formation.
4. The variable requirement for dietary Gly
equi
means that its static recommendation in poultry diets would lead to high safety margins in Gly
equi
supply or the risk of Gly
equi
deficiency. Variable recommendations for dietary Gly
equi
concentrations would help to supply birds based on their specific requirements and could reduce nitrogen emissions originating from poultry farming.
Abstract
This study aimed to distinguish between the single and interactive effects of phosphorus (P), calcium (Ca), and phytase on products of phytate degradation, including the disappearance of ...myo-inositol (MI), P, Ca, and amino acids (AA) in different segments of the digestive tract in broiler chickens. Additionally, all dephosphorylation steps from myo-inositol 1,2,3,4,5,6-hexakis (dihydrogen phosphate) (InsP6) to MI were investigated in the digesta of the terminal ileum. Unsexed Ross 308 broiler chickens were allocated to 56 pens with 19 birds per pen, and assigned to one of 8 dietary treatments. The dietary treatments included diets without (P−, 4.1 g/kg DM) or with (P+, 6.9 g/kg DM) monosodium phosphate supplementation, without (Ca−, 6.2 g/kg DM) or with (Ca+, 10.3 g/kg DM) additional fine limestone supplementation, and without or with 1,500 FTU phytase/kg feed in a factorial design. Adding Ca or P had no effect on InsP6 disappearance in the crop when phytase was added. InsP6 disappearance up to the terminal ileum (P−Ca− 56%) was decreased in P+Ca− (40%), and even more so in P+Ca+ (21%), when no phytase was added. Adding phytase removed all effects of P and Ca (77 to 87%); however, P+Ca+ increased the concentrations of lower InsP esters and reduced free MI in the ileum, even in the presence of phytase. These results indicate that mineral supplements, especially P and Ca combined, reduce the efficacy of endogenous microbial or epithelial phosphatases. Supplementation with phytase increased, while supplementation with Ca decreased 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 released MI. While AA disappearance was not affected by P or Ca, or an interaction among P, Ca, and phytase, it increased with the addition of phytase by 2 to 6%. This demonstrates the potential of the phytase used to increase AA digestibility, likely independent of P and Ca supply.
This study investigated the effects of phytase and monocalcium phosphate supplementation on the dephosphorylation of phytic acid myo-inositol 1,2,3,4,5,6-hexakis (dihydrogen phosphate); InsP6 in ...cecectomized laying hens using total excreta collection. Four corn-soybean meal-rapeseed meal-based diets were mixed with or without 6 g of monocalcium phosphate/kg, with or without supplementation of 1,500 FTU phytase/kg, and had the same calcium concentration at 39 g/kg of feed. Each diet was tested in 5 replicates using a row-column design with 10 cecectomized laying hens in 2 periods. The hens received 120 g/d of feed while being housed individually in metabolism units, and total excreta were collected for a period of 4 d. The monocalcium phosphate × phytase interaction was not significant for InsP6 degradation (P = 0.054). Phytase increased InsP6 disappearance from 13% to 83% (P < 0.001), whereas monocalcium phosphate had no effect. Concentrations of most of the lower inositol phosphate isomers in excreta were higher when monocalcium phosphate was added to the diets. The concentration of Ins(1,2,5,6)P4 in excreta was the highest among the studied partially dephosphorylated inositol phosphates with phytase supplementation and was higher than in diets without phytase supplementation (P < 0.001). Supplementation with phytase increased myo-inositol concentration in excreta (P = 0.002), whereas monocalcium phosphate had no effect. Phosphorus utilization ranged from 4% to 18% and was not significantly affected by the treatments. These results suggest that phytase supplementation markedly increased InsP6 degradation in laying hens. The cecectomized laying hen assay may be suitable for studying the effects of phytase supplementation on phytate dephosphorylation under dietary conditions when performance and phosphorus excretion are unlikely to be affected.
This study investigated the variation in amino acid (AA) digestibility and MEn of 18 samples of solvent-extracted soybean meal (SBM; 6 European, 7 Brazilian, 2 Argentinian, 2 North American, 1 ...Indian) in cecectomized laying hens. The experimental diets contained either 300 g/kg of cornstarch or one of the SBM samples. Pelleted diets were fed to 10 hens in two 5 × 10 row-column designs so that 5 replicates were obtained from each diet during 5 periods. A regression approach and the difference method were used to determine AA digestibility and MEn, respectively. The variation in the digestibility of SBM differed among AA with ranges in digestibility of 6 to 12%-units for most AA. Among the first-limiting AA, the digestibility was 87 to 93%, 63 to 86%, 85 to 92%, 79 to 89%, and 84 to 95% for Met, Cys, Lys, Thr, and Val, respectively. The range of MEn for the SBM samples was 7.5 to 10.5 MJ/kg DM. Indicators of SBM quality (including trypsin inhibitor activity, KOH solubility, urease activity, and in vitro N solubility) and analyzed SBM constituents were significantly correlated (P ≤ 0.05) with AA digestibility or MEn only in a few cases. No differences were observed in AA digestibility and MEn between countries of origins, except low digestibility of some AA and MEn for the 2 Argentinian SBM samples. These results suggest that the precision of feed formulation benefits from considering the variations in AA digestibility and MEn. Often used indicators for SBM quality and analyzed constituents were not suitable to explain variations in AA digestibility and MEn, suggesting that AA digestibility and MEn are determined by other factors.
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.
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.
Abstract
The objective of this study was to investigate the effects of supplementation with free myo-inositol (MI) or graded levels of phytase on inositol phosphate (InsP) degradation, concentrations ...of MI in the digestive tract and blood, bone mineralization, and prececal digestibility of amino acids (AA). Ross 308 broiler hatchlings were allocated to 40 pens with 11 birds each and assigned to one of 5 treatments. The birds were fed a starter diet until d 11 and a grower diet from d 11 to d 22. All diets were based on wheat, soybean meal, and corn. Birds were fed a control diet, calculated to contain adequate levels of all nutrients without (C) or with MI supplementation (C+MI), or one of 3 experimental diets that differed in phytase level (modified E. coli-derived 6-phytase; Phy500, Phy1500, or Phy3000 FTU/kg), with P and Ca levels adapted to the recommendations of the phytase supplier for a phytase level of 500 FTU/kg. The gain:feed ratio (G:F) was increased by MI or phytase in the starter+grower phase by 0.02 g/g. Prececal P and Ca digestibility, P and Ca concentration in blood serum, and tibia ash weight did not differ among treatments (P > 0.05). MI supplementation led to the highest MI concentration in the crop, ileum, and blood plasma across treatments. Phytase supplementation increased MI concentrations in the crop and ileum digesta in a dose-dependent manner and in plasma without any dose effect (P > 0.05). Prececal digestibility of some AA was increased by phytase. These outcomes indicate that MI might have been a relevant cause for the increase in G:F. 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. Simultaneously, MI seems to have no diminishing effects on InsP degradation.
The same experimental protocol was used in 4 institutions to evaluate the impact of non-phytate phosphorus (nPP) concentration in the starter diet on regression method-derived ileal P digestibility ...of soybean meal (SBM) during the subsequent grower phase. A total of 1,536 Ross 308 male broiler chickens on d 0 post hatching were allotted to 2 pre-experimental starter diets that contained 3.5 or 4.5 g nPP/kg (96 replicate cages per diet, 8 birds per cage) for 18 d. Subsequently, 576 birds from each starter diet were selected and allocated to 3 experimental semi-purified grower diets containing 400, 510, or 620 g SBM/kg (32 replicate cages per diet, 6 birds per cage) for 3 d until collection of ileal digesta. Statistical analysis was conducted as a randomized complete block design with the starter period as whole plot and the grower period as split-plot. The only significant 2-way interaction was between grower diet and experimental institution (P < 0.05) on BW gain and gain to feed ratio. The main effect of institution and grower diet impacted (P < 0.05) feed intake, the digestibility of DM, P, and calcium, and disappearance of inositol hexakisphosphate (InsP6) in the grower diets. Birds fed the 3.5 g nPP/kg starter diet had lower (P < 0.05) BW gain and feed intake during the grower period, but presented higher (P < 0.05) digestibility of P and disappearance of InsP6 compared with the birds that were fed the 4.5 g nPP/kg starter diet. Regression method-derived ileal P digestibility of SBM was determined to be 46 or 42% for the respective 3.5 or 4.5 g nPP/kg pre-experimental starter diet and was not affected by the nPP concentration or by the institution. In conclusion, the experimental protocol used in the current study resulted in similar estimates across multiple institutions and is thus endorsed for future application in studies that aim to expand the database of digestible P content in plant source feed ingredients.
The objective of this study was to determine the effects of protease origin and dosage on the prececal (pc) amino acid (AA) digestibility and the influence on composition of the microbial community ...in the small intestine. In addition, the effects of phytase supplementation were investigated. A total of 8 dietary treatments were included. The basal diet contained mainly corn and soybean meal. Three protease products were added to the basal diet, each at the level recommended by the supplier and at an 8-fold level. Phytase was supplemented in another dietary treatment. Each dietary treatment was allocated to 8 replicates of 15 birds each. The experimental diets were offered from day 15 to 21 for ad libitum consumption. The effect of protease supplementation on the pc AA digestibility depended on the protease product type and the amount supplemented. The pc AA digestibility was significantly increased by 1 protease product when supplemented at high level and when phytase was supplemented. In all the other treatments, protease supplementation had no significant influence or it decreased pc AA digestibility, when compared with the treatment with no enzymes added. In general, Firmicutes was the most abundant phylum among the ileal microbiota across all the treatments. Significant effects on microbiota composition were observed at the genus level for some but not all protease treatments and phytase supplementation. The genera Streptococcus, Lactobacillus, and uncultured Clostridiaceae were responsible for these differences. Furthermore, microbial networks established for each diet showed either high or low number of intergeneric interactions, but without a consistent enzyme effect. We conclude that enzyme supplementation effects were evident in the terminal small intestine microbiota composition, and to a lesser extent, in pc AA digestibility. However, the changes in microbiota composition and pc AA digestibility could not be correlated, indicating absence of a causal relationship.
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