Growth performance of male and female broilers fed three crude protein diet´s from 1 to 14 days of age

The crude Protein level in diets for broilers are extremely important because of their effects on body protein conversion. An experiment was conducted to evaluate the effects of crude protein on the performance of male and female broiler chicks. Seven hundred twenty day old Cobb500 chicks were arranged in a 3 x 2 factorial randomized design (three diets and the two sexes). The diets consisted in a reference diet, a high crude protein diet and a low crude protein diet with 22.4, 29.9; and 16.1% of Crude Protein respectively, all corn-soybean meal-based starter diet (Rostagno et al., 2011). At the of the experiment one bird of each plot was randomly selected (36 birds) and sacrificed for analysis of protein and body fat deposition. The variables studied was body gain, feed consumption (g) feed conversion ratio (g/g), body protein content (%) and body fat (%). Statistical analysis was performed by analysis of variance and the means were compared by Duncan test at 5% probability. There were no significant interactions between sex and crude protein content. The females, which have lower genetic potential for muscle accretion than males, did not show a significant response for the variables studied. Males showed significant response only in the body gain (p<0.001) and in the feed conversion ratio (p<0.001). For males chicks fed diets with higher levels of crude protein, such as high protein and reference diets, ended up improving body weight gain. Increase the protein level of the diets did not improve performance in relation to the reference diet, but this result could be seen in a longer trial period.