Residual Feed Intake: Challenges and Opportunities

Ongoing research in genetics and feed intake has Canadian researchers looking at residual feed intake (RFI) and feed conversion ratios of cattle. RFI, or net feed efficiency, is the difference between the actual feed intake and that predicted by regression accounting for the requirements of production and body weight maintenance.

Denny Crews of the Agri-Food Canada Research Center has been running small feeding trials on 285 Charolais-sired crossbred steers using a feedbunk system that measures feed efficiency in individual steers by scanning an electronic identification (EID) tag. They feed the steers a ration consisting of 75% barley silage.

At the end of the study, Crews said they separated out the data for the most efficient and least efficient steers. He found a 4-pound (lb.) difference in feed intake per day, but the steers’ weights at the end of the study were very close to the same. “The more efficient half of the steers gained the same amount of weight, produced carcasses with the same yield and quality grade and spent the same amount of time on feed,” he said. “But the more efficient steers consumed 390 pounds less feed than the less efficient half.”

Crews said that most researchers agree that RFI is mildly heritable (0.25-0.40). Preliminary research reports show there is a highly positive genetic correlation with mature cow efficiency, and so far they have found no antagonism with reproductive merit.

He says that currently they have only conducted RFI tests on steers, but they have plans to feed cows to look at the relationship with reproductive weight. They are also working on releasing the results from a test of about 160 bulls from five different breeds.

Crews presented the research findings in the Live Animal, Carcass and End Point Committee breakout May 30, 2003, at the 35th Annual Beef Improvement Federation (BIF) Meeting in Lexington, Ky.

— by Stephanie Veldman