Efficient feed utilization

Gary Sliworsky
Ag. Rep.

Beef cattle producers will soon have a new simpler breeding tool to select for efficient feed utilization, one of the biggest costs in beef production. Scientists at the Agriculture and Agri-Food Canada (AAFC) Research Centre in Lethbridge, in collaboration with a network of Alberta scientists and major breeding associations, are currently developing expected progeny differences (EPD) for this complex trait.

“Feed efficiency is of great economic importance to the beef industry and a breeding tool for this trait has long been sought after,” says Dr. Denny Crews, a beef quantitative geneticist with AAFC and leader of the Lethbridge research team. “We are using a measurement of feed efficiency based on intake, growth rate and size, and EPD on a pilot group of bulls from industry is expected to be available as early as 2003.”

EPD are ratings for economically important traits in beef production that represent the estimated genetic merit of an animal as a parent. Typical examples are EPD for birth weight, weaning weight, yearling weight and milk production. EPD have become broadly accepted tools in the beef industry and are now considered the standard for genetic improvement. More recently, EPD technology has received increased interest from scientists in the emerging livestock molecular genetics areas, says Crews. In fact, the new feed efficiency index has potential to tie the two sciences closer together.

“Contrary to conventional feed efficiency measurements, the new EPD measures efficiency independent of growth rate and size of cattle,” says Crews. “We can identify cattle that are genetically efficient, independent of how big they are.”

In livestock production management, feed efficiency has traditionally been calculated using the ratio of feed intake to growth, or “feed conversion ratio”. However, ratio traits do not lend themselves well to EPD methodology, and this older measure tends to favor animals with increased mature size.

“In essence, by selecting for feed conversion ratio, producers end up selecting for increased size, and that is a less sustainable strategy,” says Crews. The new EPD will offer an alternative to improve efficiency of feed utilization without any major indirect effect on mature size or maintenance requirements.

Feed efficiency is an example of a complex trait EPD that involves both quantitative and molecular genetics research at the science level.

Molecular genetics research does not generally deal with highly heritable or simple traits, where little improvement would be possible over that achieved with quantitative approaches, explains Crews. Feed efficiency, however, is affected by several components and is difficult and expensive to measure. Therefore, the addition of molecular information could likely add significantly to the usefulness of this EPD.

“Using efficient and inefficient animals identified with our measurement, our molecular genetics collaborators can determine which genes are controlling the expression of this trait,” says Crews. “The molecular information could be incorporated into the EPD to increase its accuracy.”