Feed conversion ratio

In animal husbandry, feed conversion ratio (FCR), feed conversion rate, or feed conversion efficiency (FCE), is a measure of an animal's efficiency in converting feed mass into increases of the desired output. For dairy cows, for example, the output is milk,^[1] whereas animals raised for meat – such as beef cows,^[2] pigs,^[3] chickens,^[4] and fish^[5] – the output is the mass gained by the animal. Specifically FCR is the mass of the food eaten divided by the output, all over a specified period.

"Efficiency" is customarily expressed as the ratio of useful output to input.^[6] Thus, although FCR is commonly expressed as the ratio of feed mass input to body mass output, one sometimes sees "feed conversion efficiency" (FCE) figures, i.e. kg body mass gain per kg feed intake (or, in the case of dairy animals, kg milk solids per kg feed intake).

Being a ratio, FCR is dimensionless, i.e. there are no measurement units associated with FCR.

Factors affecting FCR

FCR a function of the animal's genetics and age, the quality of the feed, and the conditions in which the animal is kept.^[2] 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).

Although FCR is commonly calculated using feed dry mass, it is sometimes calculated on an as-fed wet mass basis,^[7] (or in the case of grains and oilseeds, sometimes on a wet mass basis at standard moisture content), with feed moisture resulting in higher ratios. In cold weather, metabolizable energy requirements for warmth^[8] may result in less net energy of gain obtained from feed. Thus, when communicating FCR data for a species, it can be desirable to specify feed moisture content and provide information regarding breed, age, feed composition, and environmental conditions under which the ratio applies, to facilitate data interpretation.

Cold-blooded organisms expend fewer calories per unit mass. Fish are a common example of cold-blooded livestock.

Conversion ratios for livestock

Animals that have a low FCR are considered efficient users of feed. However, comparisons of FCR among different species may be of little significance unless the feeds involved are of similar quality and suitability.

Cattle

For cattle, a FCR range from less than 5 to more than 20 kg feed dry matter per kg gain may be encountered.^[9]

Pigs

The U.S. pork industry claims to have an FCR of 3.0-3.2.^[10][11]

Sheep

Some data for sheep illustrate variations in FCR. A FCR (kg feed dry matter intake per kg live mass gain) for lambs is often in the range of about 4 to 5 on high-concentrate rations,^[12][13][14] 5 to 6 on some forages of good quality,^[15] and more than 6 on feeds of lesser quality.^[16] On a diet of straw, which has a low metabolizable energy concentration, FCR of lambs may be as high as 40.^[17] Other things being equal, FCR tends to be higher for older lambs (e.g. 8 months) than younger lambs (e.g. 4 months).^[14]

Poultry

Poultry has a feed conversion ratio of 2 to 1.^[18] Chicken Farmers of Ontario base their Cost of Production on a FCR of 1.72^[19] Tegel Poultry of New Zealand have reported FCR as low as 1.38 on a consistent basis.^[20]

Crickets

Crickets have a low feed conversion ratio of only 1.7.^[21]

Fish

Farm raised Atlantic salmon have a very good FCR, about 1.2, according to farmed salmon industry representatives. When taking into account the true mass of material needed to make fish feed, however, the conversion ratio increases dramatically to 3:1 according to some sources.^[22]

Tilapia, typically, 1.6 to 1.8.^[18]

Rabbits

FCR 2.5 to 3.0 on high grain diet and 3.5 to 4.0 on natural forage diet, without animal-feed grain.^[23]

References

See also

• Efficiency of conversion
• Entomophagy