Abstract
Background: In Colombia, poultry production is one of the main sources of animal protein for human nutrition. The established model for feeding broilers consists of three phases, defined as pre-starter (from day 1 to 10), starter (11-21 days), and grower (from day 22 to slaughter). It is necessary that feeding programs allow the expression of genetic potential, which respond to the nutritional challenges of birds. Objective: To determine the effect of variations in the duration of the starter and grower phases on the growth performance parameters of feed intake, feed conversion, mortality, skin pigmentation, and carcass yield in broiler chickens of the Ross 308 AP genetic line. Methods: A total of 1,500 male broilers of the Ross 308 AP line were randomly assigned to five feeding plans in which variations were introduced in the feeding phase duration, feed presentation and anticoccidial program. The variables evaluated were growth performance (body weight, feed intake, and feed conversion), carcass (weight and yield), breast weight and yield, and skin pigmentation. Statistical evaluations were applied on d 28 and 40 of age. Results: On d 28 of age, statistical differences (p<0.05) were observed for body weight and feed conversion, but not for feed intake. The best weights and conversions were obtained with treatments 4 and 5. Statistical differences (p<0.05) were recorded on d 40 of age only for body weight, with values from treatments 4 and 5 being higher than that from treatment 1. In the carcass evaluation, there was only a difference (p<0.05) in carcass weight between treatments T1 and T4, with no difference between carcass and breast performances. Statistical analyses on d 28 and 40 of carcass pigmentation of chickens fed different treatments showed that there was only an effect on variables “a” (redness) and “b” (yellowness) on d 28. Conclusion: The body weight and feed conversion of the Ross 308 AP genetic line broiler chickens improved from d 22 to 28 (when extending the starter phase one week, as occurred in this study) when feed was provided in pellet with an ionophore anticoccidial. Skin pigmentation was not affected by restricting pigment intake for a week.