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

1. 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). 2. 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. 3. 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. 4. 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.