Two experiments were conducted to evaluate the performance of broilers and analyze the comparative economical effects of two concepts of protein given to two lines of broilers (Hybro G and Hybro PG) reared during cold weather, average of 16 C and RH of 72%. The broilers were fed to diets formulated based on the concept of crude protein (PB) with addition of aminoacids or on the ideal protein (PI), from 1 to 42 days of age for both sexes. The experimental design in both experiments was entirely randomized in a factorial 2 x 2 (2 protein concept vs 2 lines). The males did not show evidence and the interaction between protein vs lines for all variables studied, however, males receiving crude protein had higher fed consumption, but, had a lower weight gain and worse fed conversion compared to ideal protein, For females there was an interaction for fed conversion, where broilers of the line PG receiving PI were more efficient than those of the concept PB. For the same category, analyzing the isolated effects, there was no significant difference for feed consumption, but females of PI were heavier than those of PB. The economical analysis of the results showed that the formulation of the PI concept for both sexes is worth.
broilers; genetic lines; crude protein; ideal protein