Feed conversion rate

A measure of the ratio at which feed eaten by livestock becomes body mass. For example, a feed conversion ratio of 2 means that eating 200g of feed produces 100g of body mass. (FCR = feed intake / weight gain)

The figure varies greatly depending on how FCR is calculated. Livestock industry organizations publish relatively low figures, while environmental and animal rights organizations publish relatively high ones.

Variables involved in the calculation

Many variables enter an FCR calculation.

For example, even within the same species, younger animals tend to grow faster, so FCR varies with the number of weeks since birth (age in weeks).

It also varies depending on whether “body mass” means the weight of the living animal (live weight FCR) or the weight of its “edible parts” (edible weight FCR). Moreover, the criteria for “edible parts” vary across cultures, creating further differences: whether people eat organs, blood, some bones, and so on. Even after defining “edible parts,” the figure varies depending on whether weight is measured at the slaughterhouse (hanging weight) or as the final packaged product delivered to consumers (take-home weight).

Other variables include feed quality and moisture content, the animal’s activity level, and the number of offspring. (Source: Feed-to-meat conversion inefficiency ratio)

Feed conversion ratios for cows, pigs, and chickens

According to the relevant 2016 paper “Energy and protein feed-to-food conversion efficiencies in the US and potential food security gains from dietary changes,” feed conversion ratios for cows, pigs, and chickens are as follows (for the US).

Cows are the least efficient, followed by pigs. Chickens are relatively efficient. Of course, the most efficient method is for humans to eat vegetables directly. Veganism is not only ethical but also the most energy-efficient diet.