Body growth description of male from three broilers strains in hot climates

The body growth description is a useful tool for poultry industry's sectors, and factors like the genotypes and environment may affect this growth. The purpose of this study was to describe the body and major body parts growth of male from Cobb 500, Ross 308 and Hubbard Flex. Were used 1,080 chicks, being the treatments (3 strains) distributed in an experimental design completely randomized with 6 replicates of 60 birds each, at a stocking density of 30 birds/m?. The average temperature and relative humidity at the experimental period were 28.1 ? 0.7 ? C and 73.6 ? 13.7%, respectively. The birds were weighed weekly and the birds sampled of each pen for slaughter were fasted for 24 h, reweighed, killed, eviscerated, and dissected to obtain the cuts. There were fitted Gompertz equation for each strain to the fasted body weight (FBW), breast weight (BW), thigh weight (TW) and drumstick weight (DW). To verify the strain effect on the Gompertz curves parameters, weight at maturity (Wm), rate of maturing (B) and the time of the maximum growth rate (t*), tests have been conducted to verify the equality of parameters and identity of non-linear models (Regazzi, 2003). The tests models were: no parametric restriction, Wm in common, B in common, t* in common, Wm e t* in common, Wm e B in common and all 3 parameters in common. For the FBW, the parameter B was common between the strains (0.035 g/d/g), showed the Hubbard the highest Wm (5607. 8 g) and t* (43 d), following the Ross (Wn = 5458.3 g and t* = 42.8 d) and Cobb (Wn = 4975.1 g and t* = 41.7 d). For the BW, the most appropriate model was that all parameters were similar (Wm = 1427 g, B = 0,037 g/d/g and t* = 43.9 d), requiring the adjustment of one equation for the 3 strains. For the TW the Wm was common between the strains (Wm = 629.2 g), being the earliest Hubbard strain (43 d vs. 45 and 47 d, Ross e Cobb, respectively) due to its higher B (0.038 g/d/g) over the Ross (0.035 g/d/g) and Cobb (0.033 g/d/g). In the same way, for the DW, the Wm was common (Wm = 939.4 g), showed again the Hubbard higher B (0.030g/d/g) than Ross and Cobb (0.028 g/d/g). The results showed that the strains have particularities in their growth, for this reason the choice of strain might be directed according the production goals.