Residual Feed Intake (RFI) . . . A Selection Tool?

 By Hafla and A. Lancaster et.al

Residual feed intake (RFI) is a measure of feed efficiency that is independent of growth traits.  Seed stock producers are adopting technology to measure daily intake to assess feed efficiency of growing bulls and heifers.  Across all studies, bulls with low RFI phenotypes consumed 20% less dry matter DM and had 10% less backfat but had similar average daily gain, scrotal circumference and semen quality traits compared with high-RFI bulls.  Inclusion of RFI in selection indexes will enable selection for feed efficiency with minimal effects on growth and other performance traits.

Impacts of heifer postweaning residual feed intake classification on reproductive and performance measurements of first-, second-, and third-parity Angus beef females
– Parsons, J. Dafoe, S. Wyffels, M. Van Emon, T. DelCurto, and D. Boss
Transl Anim Sci. 2021 Apr; 5(2): txab061.

Traditionally, feed efficiency of beef cattle has been expressed as the ratio of feed intake to body weight gained (feed to gain or gain to feed); however, selection for high growth rates inevitably increases the maintenance requirements, feed requirements, and intake of cattle, with subsequent higher environmental and feed costs.  Selecting replacements with low Residual Feed Intake should produce energy-efficient cows and progeny.  This study evaluated heifer postweaning residual feed intake (RFI) classification on reproductive and performance measurements of first-, second-, and third-parity Angus beef females.

While RFI may present an opportunity to reduce feed costs, mixed results exist regarding the effect of RFI classification on reproductive performance. Damiran et al. (2018) reported a tendency for low RFI heifers to exhibit lower pregnancy rates than high RFI heifers, with fewer low RFI heifers calving in the first cycle compared to high RFI heifers. Arthur et al. (2005) and Blair et al. (2013) reported no differences between high and low RFI lines for pregnancy rate. In contrast, Randel and Welsh (2013), in a review, stated selection for low RFI results in selection of leaner heifers that reach puberty later and concluded that selection for low RFI may impair reproductive efficiency. This is supported by Arthur et al. (2005), who reported that low RFI cows calved 8 d later than high RFI cows, with the progeny of low RFI cows calving 5 to 6 d later than high RFI cows.

While our study did not observe substantial difference in beef cattle performance through the weaning of the third calf, this does not preclude potential benefits of RFI selection for cattle that eat less forage and/or utilize rangeland areas more efficiently. In fact, the real benefit of selecting for low RFI cattle may relate to intake per unit of production rather than overall production traits per se.