Residual feed intake (RFI) is a method of measuring feed efficiency that has not yet been adopted in the beef industry. RFI is calculated as the actual feed consumed minus the feed that the animal was expected to consume based on its mid-test weight and average daily gain (ADG). It is known to be phenotypically independent of weight and growth rate, thus making it a better measurement tool than feed conversion ratio (FCR), the most widely used feed efficiency measurement. The objective of this study was to compare results obtained using RFI with those of FCR to determine the best measure of feed efficiency.
RFI was calculated using three different approaches; dry matter intake adjusted for production (RFIp), dry matter intake adjusted for production and backfat thickness (RFIBF), and dry matter intake estimated with NRC net energy equations (RFINRC). Low RFIp and RFIBF bulls consumed less feed than high RFI bulls, whereas no differences existed for weight traits or average daily gain. Both RFINRC and FCR were highly correlated with weight traits and average daily gain. RFIBF proved to be the best measure of feed efficiency, as it did not have an effect on weights, gains, or backfat thickness.