Growth, feed conversion, and carcass composition in females of four broiler crosses fed starter diets with different energy levels and energy to protein ratios
Sizemore, F.G. | Siegel, H.S.
Body weight, feed conversion, and carcass composition were studied in females of four commercial broiler crosses that differed in weight at 7 wk of age. The birds were fed starter diets for the first 3 wk containing different energy levels but the same protein level (Experiment 1) or varying energy or protein to equilibrate energy:protein ratios (Experiment 2). Experiment 1 was conducted in floor pens; Experiment 2 in batteries. All birds received a common grower diet from 4 to 7 wk of age. No significant cross by starter diet interactions were found for body weight, feed conversion, carcass weight, or protein percentages. In the floor experiment, 3- and 7-wk body weights were lower in birds receiving the highest energy starter than in those receiving lower energy starters; in the battery experiment, body weights were unaffected by energy of the starter. Feed conversion was lower in the birds receiving the high-energy starter in both experiments. Carcass weights essentially paralleled live weights in both experiments; however, percentage of protein in carcasses of 7-wk-old broilers was unaffected by starter diets. Feeding a high-energy starter for the first 3 wk posthatch resulted in higher carcass fat percentages at 7 wk of age but lower absolute and relative abdominal fat pad weights. The significant cross by starter diet interactions indicated that the fastest growing broilers responded to the high-energy starter diet by a significant reduction in abdominal fat without an overall reduction in carcass fat.
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