Abstract:
In South African Bonsmara cattle, feed conversion ratio (FCR) is mostly used as a measure of feed efficiency in selection programs but has the disadvantage of being a ratio trait and unfavourably correlated to weight and mature size. Residual feed intake (RFI) overcomes both these disadvantages. The purpose of this study was to evaluate RFI as a potential trait in a selection programme by determining its correlations with growth related traits as well as other efficiency traits. Data of 5981 Bonsmara bulls that participated in centralised growth tests was analysed. In this study, RFI was calculated within contemporary groups of more than ten animals. The h2 for RFI, FCR and KR were 0.27±0.02, 0.23±0.02 and 0.18±0.02 respectively. The genetic correlation between RFI and FCR, and RFI and KR were 0.65±0.04 and 0.12±0.07 respectively. Correlations approaching zero were estimated between RFI and shoulder height (SH), body length (BL), scrotal circumference (SC), average daily gain (ADG), weaning weight (WW) and metabolic mid-weight (MMW), and a strong correlation of 0.79±0.03 with daily feed intake (DFI). This study shows sufficient genetic variation for RFI to be considered by the Bonsmara breed as a measure of feed efficiency and confirms its independence from growth and size traits.
