The requirement for sulfur amino acid by laying hens as influenced by the protein concentration

Two experiments were conducted with White Leghorn laying hens to determine the influence of the dietary CP concentration on the requirement for TSAA. Supplements of 0, .05, .1, or .15% of DL-methionine (Experiment 1) and 0, .025, .05, .075, .1, or .125% of DL-methionine (Experiment 2) were each added to corn-soybean meal diet with 13, 16, or 19% CP. Experiment 1 was conducted for 4 wk (four groups of 10 hens, 32 wk of age per treatment). Experiment 2 was conducted for 5 wk (three groups of 9 hens, 59 wk of age per treatment). Methionine supplementation significantly improved egg production in Experiment 2, and in Experiment 1, the increase in egg production approached significance (P = .077). Egg production was highly significantly improved by increasing the protein level in both experiments. Egg weight was increased by methionine supplementation at all protein levels. For Experiments 1 and 2, respectively, the estimated requirement for TSAA in order to achieve maximum egg mass (grams of egg per day) was .61 and .54% for 13% CP, .61 and .65% for 16% CP, and .68 and .73% for 19% CP. The methionine requirement for maximum egg mass in Experiment 2 was .29%, .36 and .41% for 13, 16, and 19% CP, respectively, but was not improved in Experiment 1 by increasing the concentration of protein. Feed per gram of egg, but not feed per dozen eggs, was improved by methionine supplementation at all CP levels. Body weight gain generally increased along with the CP levels and with methionine supplementation, but the methionine requirement for maximum body weight did not appear to increase along with the increase in protein concentration. The results of the present study show that the concentration of dietary protein should be considered when determining the requirement of laying hens for TSAA.