Requirement of the laying hen for sulfur amino acids.

Two experiments with individually caged laying hens were conducted to determine the requirement for TSAA. In Experiment 1, the corn-soybean basal diet contained .48% TSAA to which increasing dose levels of DL-methionine were added providing at the highest supplemental level .645% TSAA. The experimental diets were fed for 12 wk, covering the early stage of laying from 25 to 37 wk of age. In Experiment 2, a corn-soybean basal diet containing of .51% TSAA was used along with DL-methionine supplements to determine TSAA requirement during the entire laying cycle of 52 wk (25 to 77 wk of age). The highest supplemental level of DL-methionine in this experiment provided .76% TSAA. The TSAA requirement was found to be higher for maximum efficiency of feed utilization than for obtaining maximum egg production. Based on feed conversion efficiency and at an egg mass yield of 55 g per hen-day, the requirement for TSAA was estimated to be about 740 mg per hen-day, of which about 440 mg was methionine, throughout a laying period of 52 wk. It was calculated that the estimated TSAA requirement was equivalent to approximately 660 mg true digestible SAA per hen-day.

Sulphur amino acid requirement of laying hens and the effects of excess dietary methionine on laying performance.

Individually-caged laying hens were fed on maize-soya bean meal diets containing 11.50 or 12.35 MJ ME/kg with sulphur amino acid (SAA) contents varying from 5.0 to 7.0 g/kg in period 1 (0 to 20 weeks); from 5.0 to 8.0 g/kg in period 2 (21 to 36 weeks) and from 5.0 to 10.0 g/kg in period 3 (37 to 52 weeks). A SAA requirement of about 750 mg/hen d, of which about 425 mg was methionine, was found to be adequate for birds producing on average 51 g egg mass per hen d over 52 weeks. The SAA requirement was found to be higher for maximum efficiency of food utilisation than for maximum egg yield. A diet containing 140 g protein/kg adequately supplemented with methionine and lysine, could sustain laying performance almost identical to that achieved on a diet containing 167 g protein/kg. In diets with 140 g protein/kg the addition of 0.5 to 3.5 g DL-methionine/kg diet in excess of the requirement did not affect egg production adversely, but food conversion efficiency was decreased.