Improving feed efficiency is essential to increase the sustainability of livestock production: it should reduce the use of feed resources and environmental impacts. Ruminants are key players because they transform resources that are not edible for humans, such as grass, into edible resources for human consumption, such as milk or meat. Improving the use of agricultural land and feed by animals is important because the availability of arable land is decreasing and because feed represents the largest share of production costs.

Improving feed efficiency can be achieved by selecting the most efficient animals. This selection requires an estimation of the variability in feed efficiency to estimate the genetic progress, which is potentially achievable. Estimating feed efficiency requires measures of individual feed intake and what is expected of the animal for that feed. For example, a dairy cow usually uses feed to maintain her vital functions, to produce milk, but also to rebuild body reserves which are an essential source of energy after calving. To determine feed efficiency, a cow is always compared to other cows sharing the same environment.