An experiment was carried out to study the protein, fat and energy deposition profiles of male and female slow-growing broilers (ISA J-257) fed with organic diets. Feed mixtures with reduced dietary energy level and essential amino acids (EAAs) were tested. Birds were slaughtered at 0, 14, 28, 42 and 56 d of age. The whole body weight (WBW) was analyzed in each period to calculate the protein, fat and energy deposition. Gompertz growth curves were fitted to the data.
The diets did not affect the studied variables. After 28 d, males had higher WBW growth rates, and at 56 d higher energy and protein deposition rates than females, except for fat. According to the Gompertz curves, males reached higher maximum rates of WBW growth, energy, protein and fat deposition than females. But females reached earlier the maximum rates of WBW growth (11 d), of energy deposition (12 d) and of protein deposition (15 d) than males. Females reached the maximum rate of fat deposition 1 d later. The organic production of slow-growing male and female broilers requires gender different feed programs and different final body weights from 30 d of age to the slaughter age
