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 de termine the optimum dietary lysine and methionine concentrations for g rowth and breast meat yield. In the first experiment, supplementing ly sine 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, resul ted 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 ad ditional lysine and methionine supplements improved weight gain but ga ve no further improvement in breast meat yield. In the second experime nt, 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 fou nd to support optimum liveweight gain when supplemented individually. A further study was conducted to confirm that the ranges in age and bo dyweight at which breast meat yield was measured had no significant ef fect on breast meat yield. The optimum dietary concentrations of lysin e and methionine observed in these studies are higher than those recom mended by the Standing Committee on Agriculture (1987) for broilers in Australia.