Biopotency of Methionine Sources for Young Turkeys

Abstract

L-Methionine (100%) and methionine hydroxy analogue-free aeid (88%) were evaluated for biopotency compared to DL-methionine (99%) in a starter diet for Large White turkeys during 7 to 28 days of age. The basal corn-soybean meal diet contained 28% protein, .87% total sulfur amino acids, and 2974 kcal metabolizable energy/kg by calculation and .865% sulfur amino acids by analysis. In Experiments 1 (males) and 2 (females), levels of methionine supplementation were 0, .04, .10, .16, .28, .44, and 1.00%. In Experiment 3 (male and female poults), supplemental methionine levels were 0, .12, .22, .32, and .44%. Level of methionine significantly affected growth and feed efficiency in all experiments. A nonlinear regression model (exponential) was used to describe the body weight response to supplemental methionine (0 to .44%) for each source and to obtain biopotency estimates relative to DL-methionine (at 100). Based on the three studies the biopotency (± SE) of L-methionine was significantly superior to DL-methionine (131 ± 10%); the biopotency of the analogue was not significantly different from DL-methionine (96 ± 7%). Feed efficiency was similar for all sources in Experiments 1 and 3. In Experiment 2, differences in feed/gain were detected among the three sources, where the mean values were in the order: analogue>DL-methionine>L-methionine.