Challenges in Measuring Feed Efficiency

The term feed efficiency is vague, and is defined differently by people. Historically, feed efficiency has been defined as the feed:gain (F:G) ratio or the inverse (G:F). Indexes have been developed to rank animals for feed efficiency. These indexes include residual feed intake (RFI) and residual gain (RG). The use of these measures of feed efficiency in genetic selection may be genetically correlated with other traits that are beneficial or antagonistic to beef production. Regardless of how feed efficiency is defined, an accurate measure of feed intake and growth are required for their calculation. Another potential approach toward genetic selection is to incorporate both feed intake and growth into a genetic selection index that weights the traits to match a production system. Most measures of feed efficiency have been made on growing animals. Limited information is available on the preferred time in the growth curve to measure intake and growth, nor is there a good assessment of how repeatable these measures are across ages and diet. There is also limited information regarding selecting for growth efficiency and its impact on the production efficiency of the cow. The expense of collecting individual feed intake data has made it a candidate for developing genetic markers to estimate intake. The regulation of feed intake and rate of growth are both polygenic traits making it difficult to determine the mechanism associated with variation in these traits across populations. Nongenetic factors such as diverse bacterial populations along the gastrointestinal tract may also contribute to differences in feed efficiency. USDA is an equal opportunity provider and employer.