Abstract
Research was conducted to determine the extent to which the dietary protein may be reduced with adequate methionine and lysine supplementation. Five hundred broiler chicks were kept on commercial starter diet for a pre-experimental period of twently-eight days. On day-29 post hatching, one hundred and sixty mixed chicks were randomly allotted to four experimental treatments with four replicates per treatment. Chicks were fed four different isocaloric diets formulated to contain 20, 18, 16 and 14% crude protein with appropriate supplementation so as to maintain 1.0% lysine, 0.72% methionine+cystine and adequate methionine in each case. Data on body weight gain, feed consumption, feed efficiency and feed cost per kg body weight gain were recorded. On day 46, three birds per replicate were randomly selected and slaughtered to collected abdominal fat and dressing weight of each bird. The mean body weight gain per chick at the end of experimental period was 1062, 1064, 1074 and 914 g for treatment A, B, C and D, respectively. Results indicated that lowering the crude protein level of the diet-up to 16% with adequate methionine and lysine supplementation had no deleterious effect on body weight gain. There was significant drop in weight gain when the level of crude protein was further reduced to 14%. The mean feed consumption per chick during the experimental period was 2785, 2801, 2836 and 2818 g for treatment A, B, C and D, respectively. The mean feed-gain ratio was 2.62, 2.63, 2.64 and 3.08 for treatment A, B, C and D, respectively. There were no significant differences in the feed efficiency among treatment A, B and C. However, feed efficiency was significantly poor in treatment D (14% crude protein diet). The mean abdominal fat weight per bird was 28.8, 28, 28.1 and 32.2 g for treatment A, B, C and D, respectively. Mean abdominal fat expressed as percent of dressed weight was 2.33, 3.00, 3.02 and 3.58% for treatment A, B, C and D. respectively. The mean dressing percentage at the end of experimental period was 58.0, 57.7, 57.9 and 57.8 percent for treatment A, B, C and D, respectively. The mean cost per kg body weight gain was Rs. 26.46, 26.32, 25.56 and 30.08 for treatment A, B, C and D, respectively. The feed cost per kg body weight gain was the lowest for treatment C having 16% crude protein. These results indicated that the NRC (1984) recommendation of 20% protein for finisher period may be reduced with the required level of methionine and lysine supplementation.
