Choline and methionine supplementation of layer diets varying in protein content.

Two experiments were conducted with White Leghorn laying hens to evaluate choline and methionine addition to diets containing various crude protein (CP) levels. Corn-soybean meal diets containing 25 g/kg meat and bone meal were used in all experiments. Either choline or methionine supplementation at 1.0 g/kg improved egg production and feed:egg ratio of hens fed 140 g/kg CP from 23 to 35 weeks of age in Experiment 1. The magnitude of response from methionine was significantly greater than that from choline. Egg production and feed: egg ratios were not affected by these supplements in diets containing 160 g/kg CP. Added methionine also improved egg yield and egg weight at both levels of CP, whereas choline had no effect. In Experiment 2, .5 g/kg choline or methionine increased egg weight of hens fed 140 g/kg CP from 33 to 45 weeks of age, but these supplements had no effect in diets containing 160 g/kg CP. In phase 2 of this experiment, either choline or methionine at 1.0 g/kg improved egg production and egg yield of hens fed either 150 or 130 g/kg CP from 45 to 57 weeks of age. The responses from methionine were greater than those from choline. Methionine also improved egg weight at the lower protein level, whereas choline had no effect. The results of this study indicate that laying hens respond to either dietary choline or methionine supplementation; the response to methionine was greater, however, than the response to choline.(ABSTRACT TRUNCATED AT 250 WORDS)