Selection for growth rate in pigs on restricted feeding. Genetic parameters and correlated responses in residual feed intake.

Abstract

Residual Feed Intake (RFI) represents the deviation of the actual ad libitum food consumption of each animal from that predicted on the basis of its growth rate alone or combined growth rate and backfat. After four years of selection of a line for high and one for low post weaning growth rate on restricted feeding, the high line exhibited a significant reduction in residual feed intake relative to the low line. This indicated a lower energy requirement for maintenance in the high than the low line, possibly due to reduced physical activity of the animals. Estimates of genetic parameters showed that RFI was moderately heritable. Genetic correlations of RFI with backfat and food conversion ratio were moderately to highly positive, suggesting that selection for low RFI would improve carcass lean content and efficiency of food utilisation.