Feed conversion ratio

In animal husbandry, feed conversion ratio (FCR) or feed conversion rate is a ratio or rate measuring of the efficiency with which the bodies of convert animal feed into the desired output. For dairy cows, for example, the output is milk, whereas in animals raised for meat (such as beef cows, pigs, chickens, and fish) the output is the flesh, that is, the body mass gained by the animal, represented either in the final mass of the animal or the mass of the dressed output. FCR is the mass of the input divided by the output (thus mass of feed per mass of milk or meat). In some sectors, feed efficiency, which is the output divided by the input (i.e. the inverse of FCR), is used. These concepts are also closely related to efficiency of conversion of ingested foods (ECI).

Feed conversion ratio (FCR) is the ratio of inputs to outputs; it is the inverse of "feed efficiency" which is the ratio of outputs to inputs. FCR is widely used in hog and poultry production, while FE is used more commonly with cattle. Being a ratio the FCR is dimensionless, that is, it is not affected by the units of measurement used to determine the FCR.

FCR a function of the animal's genetics and age, the quality and ingredients of the feed, and the conditions in which the animal is kept, and storage and use of the feed by the farmworkers.

As a rule of thumb, the daily FCR is low for young animals (when relative growth is large) and increases for older animals (when relative growth tends to level out). However FCR is a poor basis to use for selecting animals to improve genetics, as that results in larger animals that costs more to feed; instead Residual Feed Intake (RFI) is used which is independent of size. RFI uses for output the difference between actual intake and predicted intake based on an animal’s body weight, weight gain, and composition.

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