Residual feed intake as a feed efficiency selection tool and its relationship with feed intake, performance and nutrient utilization in Murrah buffalo calves

Residual feed intake (RFI) is the difference between the actual and expected feed intake of an animal based on its body weight and growth rate over a specific period. The objective of this study was to determine the RFI of buffalo calves using residuals from appropriate linear regression models involving dry matter intake (DMI), average daily gain (ADG) and mid-test metabolic body weight. Eighteen male Murrah buffalo calves of 5-7 months were selected and fed individually. A feeding trial using ad libitum feeding of total mixed ration (TMR, concentrate/roughage = 40:60) was conducted for 52 days in which the daily DMI, weekly body weight (BW) and growth rate of the calves were monitored. RFI of calves ranged from -0.20 to +0.23 kg/day. Mean DMI (in grams per kilogram of BW0.75) during the feeding trial period was significantly (P < 0.05) lower in low RFI group (79.66 g/kg BW0.75) compared to high RFI (87.74 g/kg BW0.75). Average initial BW, final BW and mid-test BW0.75 did not differ (P > 0.05) between low and high RFI groups. Over the course of a trial period, low RFI group animals consumed 10 % less feed compared to high RFI group of animals, yet performed in a comparable manner in terms of growth rate. Metabolizable energy for maintenance (MEm) was found to be significantly (P < 0.05) lower in low RFI group (13.54 MJ/100 kg BW) as compared to that of high RFI group (15.56 MJ/100 kg BW). The present study indicates that RFI is a promising selection tool for the selection of buffaloes for increased feed efficiency.