Sexual dimorphism in the growth pattern of broilers under different dietary and housing conditions
Two hundred and seventy day old broiler chicks were randomly distributed among three dietary treatments (iso-nitrogenous high and low energy straight-run diets and a conventional broiler diet) and two housing conditions (the cage and deep litter) to study the comparative growth patterns between the male and female broilers. Each treatment was replicated thrice at 15 birds per replicate. The chicks were raised for 8 weeks. There were significant interactions (P < 0.05) between age, diet, housing location and sex. The male broilers had significantly (P < 0.05) higher body weight gains than the females especially at the finisher phase. While the females performed better on high energy diet at both phases, the males responded to low energy diet at the starter phase and high energy at the finisher, hence a narrower male: female divergence ratic at the finisher phase. Generally, location had no significant effect (P > 0.05) on body weight gains ( 215.0g vs 214.3bird/wk - cage vs floor). However, males gained slightly more weight in the cage while females gained slightly more on deep, litter. Both recorded higher gains on the floor at the starter phase and in the cage at the finisher period. Coefficient of variation was respectively lower for the male broilers, birds in the cage, birds at the finisher phase and lowest for birds on conventional diet. Feed consumption was significantly higher (P<0.05) for low energy diet (68.9 vs 65.1g/bird/day) as well as by birds in the cage (69.4 vs 64.5g/bird/day) with correspondingly lower utilization rate.
Key Words: Sexual dimorphism, broilers, growth patterns, diets, housing.