Variability in residual feed intake and nutrient utilization in Murrah buffalo heifers

A feeding trial with 18 Murrah buffalo heifers (238 ± 63 kg; 1.7 ± 0.4 years old) was conducted for 57 days, and feed intake and body weight were recorded followed by 7 days of urine and feces collection. Heifers were grouped into low (RFI-I) and high (RFI-II) feed efficiency groups by regressing DMI (g head^-1 day^-1) on BWG (g head^-1 day^-1) and mid-test MBW (kg). RFI-II heifers had slightly higher DMI (g head^-1 day^-1 and expressed per unit of BW, %BW, MBW, mid-test BW, and mid-test MBW) and all associated nutrient intakes, BWG, feed efficiency traits (FCR, CPCR), digestibility of nutrients, and retentions of crude protein and fat over RFI-I heifers. The corresponding intake values (kg head^-1 day^-1) for RFI-I versus RFI-II were the following: DMI (6.73 ± 0.56 vs 6.51 ± 0.50), CPI (0.99 ± 0.008 vs 0.97 ± 0.07), DOMI (5.06 ± 0.47 vs 5.11 ± 0.42), and TDNI (4.95 ± 0.47 vs 5.00 ± 0.42). BWG (669 ± 52 vs 776 ± 47 g head^-1 day^-1), feed efficiency traits (FCR: 10.32 ± 1.16 vs 8.77 ± 1.04 and CPCR: 1.52 ± 0.17 vs 1.30 ± 0.16), N balance (38 ± 9 vs 45 ± 8 g N head^-1 day^-1), and protein and fat retentions (239 ± 57 vs 282 ± 51 g CP head^-1 day^-1 and 430 ± 6 vs 494 ± 59 g fat head^-1 day^-1) of RFI-I were less than RFI-II heifers, respectively. Based on the predicted RFI values, RFI-II buffalo heifers could be selected for feed efficiency.