The effect of dietary lysine and methionine concentrations on the growth characteristics and breast meat yields of Australian broiler chickens

Two experiments were conducted with an Australian broiler strain to determine the optimum dietary lysine and methionine concentrations for growth and breast meat yield. In the first experiment, supplementing lysine to 14.1 and 13.0 g/kg in combination with methionine supplemented to 6.2 and 5.3 g/kg in starter and finisher diets respectively, resulted in significant improvements in breast meat yield with no effect on growth rate. Increasing the crude protein concentration by increasing the concentrations of all indispensable amino acids to balance the additional lysine and methionine supplements improved weight gain but gave no further improvement in breast meat yield. In the second experiment, dietary concentrations of 13.1 and 12.5 g lysine/kg and 6.5 and 5.1 g methionine/kg in starter and finisher diets respectively, were found to support optimum liveweight gain when supplemented individually. A further study was conducted to confirm that the ranges in age and bodyweight at which breast meat yield was measured had no significant effect on breast meat yield. The optimum dietary concentrations of lysine and methionine observed in these studies are higher than those recommended by the Standing Committee on Agriculture (1987) for broilers in Australia.