Progress toward incorporating residual feed intake into the New Zealand national breeding objective for dairy cattle: Genetic parameters in half-sib 6-9 month old Friesian bulls and heifers

Abstract

To investigate the potential to select for feed conversion efficiency in dairy cattle, we measured daily feed intake and body liveweight on 73 bull and 246 half sib heifer calves in a feeding trial using ad libitum Lucerne cube feed at the Westpac Taranaki Agricultural Research Station in Hawera, New Zealand. We measured feed consumption using automated systems, weighed all animals thrice weekly, and estimated residual feed intake (RFI) as the residual from a regression of daily dry matter intake (DMI) on average daily gain (ADG) and metabolic body weight (MBW^0.75). Using ASReml, we estimated the sex-specific additive genetic variances and heritabilities using univariate animal models as 0.05 and 0.13 ± 0.14 for the heifers, and 0.09 and 0.18 ± 0.57 for the young bulls. We also used a bivariate animal model that treated the RFI of the two sexes as different traits to estimate the genetic correlation between young bulls and heifers as 0.93 ± 1.46. Despite the high standard errors around the genetic parameter estimates due to small sample size, our results provide a preliminary indication that RFI is largely controlled by the same genes in both sexes and that genetic variation in RFI in Friesian dairy cattle is sufficient to support a response to selection in female relatives of elite young bulls.