Interactions of the branched-chain amino acids. 1. Influence of dietary isoleucine and leucine on the valine requirement of male Cobb MV × 500 broilers for a 29- to 42-day finisher period

Abstract

Branched-chain amino acid requirements have traditionally been determined using dose-response titrations without accounting for the influence of branched-chain amino acid antagonism. As recent data has indicated that inherent levels of the non-tested amino acid may influence response curves in diets mimicking industry, these methods may result in over or under estimation of requirement values. Therefore, an experiment was conducted to determine if dietary levels of isoleucine and leucine influence 29 to 42 day valine needs through the implementation of a 5 × 2 × 2 factorial design. Twenty diets were fed to 7 replicate pens of 12 broilers. Body weight gain, feed intake, and FCR were determined for the 29 to 42 day period, and carcass traits were assessed on day 44. Valine × isoleucine and valine × leucine interactions were observed for BW gain and total breast yield ( P < 0.10). Body weight gain requirements ranged from 73 to 81 Val/Lys, whereas responses for total breast yield were generally negative. A 3 way interaction was observed for FCR in which requirements varied from 75 to 82 Val/Lys. These interactions indicate that formulation strategies based on previous data concerning valine or isoleucine may not produce the desired response in Cobb MV × 500 broilers and that the branched-chain amino acids should be considered as a whole and not individually.