Abstract
The recent breeding programs for livestock and poultry projects have aimed at maximizing productivity and minimizing gross costs. It is well known that feed represents the main variable component affecting the productive process. The animal's requirements can be divided into needs for maintenance and productive requests. Consequently, recent breeding programs have aimed at reducing production costs through genetic improvements in residual feed intake (RFI). A bird that consumes less feed than expected for production and preservation requirements has a negative residual feed intake (-RFI). This case is desirable for decreasing feed costs in animal and poultry projects. Chickens with low predicted feed intake (PFI) (R-) need less feed to reach a similar body weight and production performance. On the other hand, birds that eat more feed than expected have a positive RFI. Accordingly, the latter birds (+RFI) must be avoided by breeders via effective selection programs. (C) 2021 Published by Elsevier Ltd.