Technical Keynote Session 3
Feed Efficiency Research
The University of Idaho and the Red Angus Association of America (RAAA) have recently launched a research project that aims to understand the biological mechanisms that drive variation in feed efficiency with a focus on product quality. Rod Hill, department of animal and veterinary science at the University of Idaho, spoke about feed efficiency and this project May 2 at the 2009 Beef Improvement Federation (BIF) symposium in Sacramento, Calif.
The beef industry has traditionally used gross feed efficiency, calculated by dividing feed consumed by pounds gained, to evaluate efficiency, Hill said. However, this method is highly correlated with growth rate and favors genetically larger cattle.
Rod Hill, University of Idaho.
Hill said that residual feed intake (RFI) has emerged as a new measure of efficiency that is independent of growth and maturity patterns. It compares actual feed intake to expected feed intake based on growth and body weight. High-RFI animals eat more than expected based on their growth and body weight, whereas as low-RFI animals eat less but produce the same weight gain, he explained. RFI is moderately heritable, around 0.3-0.5.
“RFI is a valuable measure of efficiency because it can identify animals that consume less feed but weigh the same at harvest,” Hill said. However, he said that little is definitively known so far about RFI’s correlation with other economically relevant traits of production, reproduction and end product.
The University of Idaho research project aims to learn more about RFI’s correlation with the RAAA’s expected progeny difference (EPD) for maintenance energy (ME). ME is a derived trait that provides a measure of maintenance and factors in cow weight at weaning corrected to a body condition score (BCS) of 5 and milk EPD. Hill said the project is looking at this relationship because maintenance accounts for more than 40% of the variation in RFI from animal to animal.
The research project compares bulls with low ME and high ME, following their steer progeny through harvest to evaluate end-product quality. Results so far confirm that there is no relationship between RFI and average daily gain (ADG), though it is positively correlated with dry-matter intake (DMI). Hill said that there is a potentially unfavorable relation between RFI and marbling since animals with low RFI tend to be leaner. He cautioned against single-trait selection for RFI since it could result in a less ideal end product, though more research is needed on the potential relationship.
“We have no formal conclusions yet about the relationship between ME and RFI since our data was obtained from a small population,” Hill concluded.
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The 41st BIF Research Symposium and Annual Meeting was hosted by the California Beef Cattle Improvement Association and the California Cattlemen's Association. For more information, visit www.bifconference.com or www.calcattlemen.org/bif2009.html.
