Growth curve and body composition of broiler breeder hens

Broiler breeder hens do not express their maximum genetic potential due to feed restriction. This is necessary because broiler breeder hens have faster growth and higher feed intake in comparison to commercial laying hens and these characteristics are negatively correlated to reproductive performance. Thus, the aim of this study was to describe the growth curves and body composition of broiler breeder hens submitted to a controlled feeding program. For this trial, 300 day-old broiler breeder chicks (Cobb 500) were randomly distributed in 10 floor pens (30 birds/pen).The experiment lasted 28 weeks. All birds were submitted to the same feeding program from 0 to 28 weeks of feeding program (daily restriction) afterwards. All birds were weighed and five birds were randomly sampled and slaughtered using CO₂ (after 36 h of fasting) at 1, 4 and 11 weeks of age, and weekly from 18 to 28 weeks of age. Sampled carcasses were weighed before and after defeathering for carcass analysis. The protein and lipid composition of these samples were used to estimate the growth parameter of these chemical components. Growth parameters were estimated using the Gompertz function:, where W_(t) is weight at time t, t is the age of bird (day); W_m is the weight at maturity (g), b is the rate of maturity (day^-1), t^* is the age at maturity (days) and e is the Euler's number. The W_m presented the following results: 4.8854 kg for body weight, 0.704 kg for protein weight and 0.860 kg for lipid weight. The maturity of body weight was achieved at 82.3 days whereas protein weight reached maturity at 77.7 days, when the maximum muscle synthesis occurs. Due to feed restriction, the lipid weight achieved the maturity only at 149.4 days. The estimated b values were 0.016, 0.014 and 0.009 for body, protein and lipid weight, respectively. The b for protein weight was greater than b value of body and lipid weights. Therefore, it is concluded that feed restriction promotes maximum production of the broiler breeder, because breeders fed in excess to its requirements causes an increase in lipid deposition and decrease the reproduction performance.