The present research was defined to evaluate the residual feed intake (RFI) of white and brown groups of aged layers, between 85 to 90 weeks of age. A completely randomized design was used, with two treatments and 15 replicates, of one hen per replicate, for individual control. The treatment consisted of two genetic groups, brown and white (W-80), from Hy Line. Performance, egg quality, biometry visceral, body composition, energy partition, RFI, and residual metabolizable energy intake (RMEI) were evaluated. The results showed that egg weight was the main factor responsible for the difference between genotypes, affecting the production of the egg mass, yolk weight, and eggshell weight, as well as measures related to utilization efficiency (p < 0.05). The size of the uterus + vagina was larger for white layers (p < 0.05). The values obtained for RFI and RMEI were lower (p < 0.01) for white layers. While brown layers did not present hens with low RFI, 64.3% of the hens were classified as high RFI. The differences shown in this research between white and brown layers are smaller than in the past and show a tendency towards similarity; however, the economic impacts of the current differences are significant and must be considered.
Silva et al. (Sat,) studied this question.