Ileal amino acid digestibility in poultry
Abstract
A series of poultry studies was conducted to confirm the possible variation in ileal AA digestibility between species as well as estimation methods used. In the first study, the apparent ileal AA digestibility of 6 feedstuffs including corn, wheat, DDGS, CM, SBM, and MBM were determined for White Pekin ducks in a 5-d experiment. There were considerable differences among feedstuffs in the digestibility of their AA for ducks, which indicated that digestible AA rather than total AA contents in the feedstuffs are more relevant measurements to describe bioavailable AA contents for poultry. The second study was conducted to determine response in digestibility of DM and the AA composition of ileal endogenous flow of 26-d-old broilers to NFD formulated with different ratios of corn starch to dextrose. The results showed that the ratio of corn starch to dextrose in a NFD may affect estimates of ileal endogenous flows of N and AA. Thirdly, broiler chickens and White Pekin ducks were used in a 5-d trial to test additivity of the AID and SID of AA in corn and SBM. The results indicated that AID of some AA for corn and SBM were not additive in the mixed diet but SID values were additive irrespective of the ingredients and species used. The next study was conducted to compare ileal AA digestibility of SBM and CM for broilers and ducks using the regression method based on apparent or standardized ileal AA digestibility. The results of this study showed that ducks have higher basal endogenous AA losses compared with broiler chickens as well as higher ileal AA digestibility estimates derived from the SID-based regression approach indicating that broiler ileal AA digestibility values should not be used in formulating duck diets. Lastly, two studies were conducted to investigate efficacy of exogenous enzymes including phytase and β-mannanase on nutrient digestibility. The results from these studies showed that phytase supplementation improved protein efficiency ratio of broilers fed diets containing CM as the sole protein source but did not affect the ileal digestibility of AA in CM determined by the regression method. The results also indicated that supplementing β-mannanase may improve gain and energy utilization of broilers whereas it may not affect ileal AA digestibility. In conclusion, the overall results from these studies showed that there are considerable variations in digestibility of AA between feedstuffs, species, and estimation methods and that SID corrected for basal endogenous AA losses determined by a standard NFD method should be considered as a reliable measurement. In addition, the results indicated that ileal AA digestibility determined with broilers should not be used for formulation of duck diets.
Degree
Ph.D.
Advisors
Adeola, Purdue University.
Subject Area
Animal sciences
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