Residual feed intake measured as replacement heifers is indicative of residual feed intake measured as mature cows

This study aimed to quantify the relationship between residual feed intake (RFI) measured in 500 heifers and subsequently as mid-gestation cows at the Roy Berg Kinsella Research Station (KIN; n = 227) and Lacombe Research and Development Centre (LRDC; n = 273). Heifers were initially tested for RFI adjusted for end of test rib fat (RFI fat ) at 8–12 months of age and then again as 3-year-old first-calf heifers at KIN and as 4–13-year-old cows at LRDC. Heifer RFI fat measured in drylot on a forage diet was associated ( R 2 > 0.53; P < 0.001) with RFI fat measured again as older cows. Each 1 kg DM day −1 change in heifer RFI fat equaled 0.48 ± 0.10 and 0.75 ± 0.19 kg DM day −1 change in cow RFI fat for KIN and LRDC, respectively. Linear effects were also reported for RFI fat component traits, where DMI ( P < 0.001), ADG ( P < 0.060), mid-test metabolic weight ( P < 0.001), and end of test rib fat ( P < 0.001) measured as heifers were related when measured again as older cows. In addition, the linear effects of heifer RFI fat on cow RFI fat were constant across cow age groups from 4–10 years of age. These results show that selection for RFI in heifers will result in cows that are also more feed efficient.