Buffalo heifers selected for lower residual feed intake have lower feed intake, better dietary nitrogen utilisation...

This study was conducted to evaluate the utilisation of the residual feed intake (RFI) as a feed efficiency selection tool and its relationship with methane emissions. Eighteen Murrah buffalo (Bubalus bubalis) heifers were fed ad libitum with total mixed ration (TMR) for 120 days. Based on linear regression models involving dry matter intake (DMI), average daily gain (ADG) and mid-test metabolic body size (MBW^0.75 ), heifers were assigned into low and high RFI groups. The RFI varied from -0.09 to +0.12 kg DM/day with average RFI of -0.05 and 0.05 kg DM/day in low and high RFI heifers respectively. Low RFI heifers ate 11.6% less DM each day, yet average daily gain (ADG) and feed utilisation were comparable among low and high RFI groups. Low RFI heifers required significantly (p < .05) less metabolizable energy for maintenance (MEm) compared to high RFI heifers. Apparent nutrient digestibility showed non-significant difference (p > .05) among low and high RFI groups. Although the nitrogen balance was similar among heifers of low and high RFI groups, nitrogen metabolism was significantly higher (p > .05) in high RFI heifers. Comparison of data from heifers exhibiting the low (n = 9) and high (n = 9) RFI showed that the low RFI heifers have lower enteric methane production and methane losses than high RFI heifers. In conclusion, results of this study revealed that selection of more efficient buffalo heifers has multiple benefits, such as decreased feed intake and less emission of methane.