Estimation of amino acid digestibility and its usefulness in swine feed formulation

• Main Author: Bellaver, Claudio
• Format: Dissertation
• Language: English
• Published: ProQuest Dissertations & Theses 01-01-1989
• Subjects: Animal sciences; Livestock
• ISBN: 9798206786316

The practical utility of digestible amino acid values in swine feed formulation has been a subject of debate among nonruminant nutritionists. Unfortunately, little has been done experimentally to compare values obtained for similar feedstuffs by different methodologies or to validate the usefulness of these values in the formulation of diets. Thus, the first objective of this thesis was to develop a data base of amino acid and protein digestibilities using several common feedstuffs and four methodologies. These values were then compared by correlation analysis and finally, the values were used in the formulation of diets for feeding studies to test the hypothesis that diets of equal "digestible" amino acid content will support equal growth in pigs. Four methods for predicting amino acid utilization were used. Two in vivo procedures, swine ileal sampling and precision-fed, cecectomized rooster excreta collection, were used to obtain digestibility values. A chick bioassay procedure was employed to estimate bioavailability of lysine in the test feed ingredients. And, an in vitro enzyme incubation method was used to estimate potential protein hydrolysis. The feedstuffs used in each assay were: corn, wheat bran (WHB), two soybean meals (SBM), cottonseed meal (CSM), poultry by-product meal (PBP) and two meat and bone meals (MBM). In order to test the hypothesis that diets formulated to be equal in digestibility for key amino acids will support equal growth performance of pigs, two growth experiments were conducted. The control diet in each experiment was prepared with corn and soybean meal. Diets were formulated with alternative ingredients to contain the same levels of lysine, threonine, tryptophan and methionine plus cystine, as the control diet. Because feed intake was depressed when the diets formulated with alternative ingredients were fed, a pair-feeding experiment was conducted. When fed at equal amounts, the growth difference between pigs fed the control diet or the diet formulated with alternative ingredients was reduced. This thesis provides evidence that correlation does exist between various methods used for estimating amino acid digestibility or availability. Alternative ingredients, however, may not provide similar rate and efficiency of gain when formulated to provide equal digestible amino acid content as a corn soybean meal-based diet. (Abstract shortened with permission of author.)