Residual feed intake (RFI) is a measure of feed efficiency that is independent of growth traits.  Different RFI has been tied to differences in nutrient digestibility, production of volatile fatty acids and methane in the rumen, feeding behavior, and differences in the microbial population in the digestive tract. Research from Texas showed that steers and heifers with low RFI had 19% lower feed consumption with the same average daily gain. Feed digestibility (along with digestibility of protein and fiber) was increased by 4% and ruminal methane production was reduced by 14% in low RFI (or more efficient) cattle.

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.

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. Research by [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. Another study by 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 days later than high RFI cows, with the progeny of low RFI cows calving 5 to 6 days later than high RFI cows.

While the 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.

Improving the feed efficiency of a beef cattle herd can mean big savings for producers. One way to achieve this goal is to select breeding bulls that are naturally feed-efficient, since 80 to 90 per cent of the genetic improvement in a herd comes through the sires.

On average, it costs $50 less over 112 days to feed an efficient bull compared to an inefficient one. An efficient bull will pass on superior genetics for feed efficiency to his progeny, which will be realized as feed savings for calves in the feedlot and for replacement heifers entering the cowherd. Feed is a major expense for cattle producers, second only to fixed costs. With 75 per cent of the total feed cost used for maintenance in breeding cows, improving feed efficiency can have a big economic effect. Improving feed efficiency can have a big economic effect A 5 per cent improvement in feed efficiency could have an economic effect four times greater than a 5 per cent improvement in average daily gain. Improving feed efficiency will have an effect on the unit costs of  production and the value of breeding stock, embryos,  semen and feeder animals.

An economic analysis conducted in Canada, showed the economic potential, accrued after 15 to 25 years of selection for RFI, was estimated at $109 million annually for Alberta’s feeder cattle industry and at least as much for cow-calf producers. Improving RFI is also expected to reduce methane and manure emissions from cattle by 15 to 20 per cent, which, in turn, may result in new agriculture investment due to greenhouse gas credits.



Sources:

Relationships between feed efficiency, scrotal circumference and semen quality traits in yearling bulls – Hafla, A. Lancaster, G. Carstens, D. Forrest, J. Fox, T. Forbes, Mike Davis (OSU), R. Randel, and J. Holloway, Journal of Animal Science. 2012.90:3937–3944

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.

Residual Feed Intake (Net Feed Efficiency) in Beef Cattle, Prepared by  Alberta Agriculture and Forestry.