Genetic variation in starch digestion in feedlot cattle and its association with residual feed intake

Abstract

Steer progeny of lines selected for either low residual feed intake (high efficiency) or high residual feed intake (low efficiency) were grown out in a feedlot and measurements of feed intake, liveweight gain and faecal parameters were combined to investigate associations with starch digestion. There were significant differences between sire progeny groups in faecal pH and faecal dry matter content indicating genetic differences in starch digestion. This variation occurred even after differences in dry matter intake were accounted for. Furthermore, there was a significant association between these faecal parameters and mid-parent Estimated Breeding Values for residual feed intake, rib (12/13th) fat depth and rump fat depth (Australian P8 site). This confirmed an association between parameters believed to describe starch digestion and genetic variation in important production traits. Low faecal pH and faecal dry matter content were associated with higher residual feed intake (i.e. lower efficiency).