|CORZO, A - Mississippi State University|
Submitted to: Poultry Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/10/2012
Publication Date: 3/15/2012
Citation: Kim, E.J., Corzo, A. 2012. Interactive effects of age, sex, and strain on apparent ileal amino acid digestibility of soybean meal and an animal by-product blend in broilers. Poultry Science. 91:908-917.
Interpretive Summary: Formulation of diets on a digestible amino acid basis allows for precision formulation of broiler diets, which can, in turn, decrease feed costs and allow for better predictions on performance. The protein requirement for broilers is actually a requirement for amino acids, which should be set at appropriate levels to account for growth and muscle accretion. The objectives of this study were to determine what factors can affect the digestibility of amino acids in broilers. The effects and interactions of age, sex, and strain on the amino acid digestibility of soybean meal and an animal by-product meal were evaluated. Broilers at 3 and 6 wks, from two different broiler strains and separated by sex, were fed experimental diets that were formulated to only contain each feed ingredient as its sole source of protein. Upon completion of the experiments, birds were euthanized and intestinal contents were collected and analyzed for amino acids. For soybean meal, the effects of age, sex, and strain did not significantly affect amino acid digestibility. However, these three factors interacted together to affect amino acid digestibility. For the animal by-product blend, the effect of age and strain affected amino acid digestibility of broilers, but none of the three factors interacted to affect digestibility. Factors such as age, sex, and strain, should be taken into account when formulating diets on a digestible amino acid basis because it will allow producers to minimize feed costs by not overfeeding protein and amino acids.
Technical Abstract: The objectives of this study were to determine if age, sex, and strain of broilers affects the apparent ileal amino acid digestibility (AID) of soybean meal (SBM) and an animal by-product blend (ABB). Chicks from two broiler strains, a commercially available and another in the test phase, were obtained from a common hatchery, feather-sexed, and placed into floor pens. The birds received common diets while on floor pens. Birds were transferred to metabolism crates for two ileal digestibility trials conducted at 3 and 6 wk of age. Two semi-purified diets were formulated with each of the feed ingredients providing all the amino acids (AA) in the diets. Diets were formulated to contain 20% CP with chromic oxide added to the diet at 0.30% as the indigestible marker. The experimental diets were fed for a 72 hr period after an overnight fast to 8 replicate cages of 5 birds per cage. Upon completion of the experimental periods, i.e., d 22 and 43 birds were euthanized and ileal digesta samples were collected and pooled by pen, frozen, lyophilized, and analyzed for AA and chromium concentrations. For SBM, no main effects were observed for age, sex, or strain; however, significant (P=0.05) three-way interactions were observed for several dispensable and indispensable AA. Analyses of these interactions indicate the AID of SBM may be different for males of the test strain, particularly at 42 d of age. For the ABB, only main effects were significant for each AA, with the exception of Ile and Tyr. Main effect of strain was observed for most of the AA, showing that the commercially available strain had higher AID than the test strain. Also, significant main effect of age indicated that the AID for ABB was higher at 42 d than 21 d. Evaluation of these two ingredients showed thatw age, sex, and strain may impact digestibility of feedstuffs and should all be considered, collectively for some cases, in future investigations as important sources of variation.