# Feed conversion ratio

In animal husbandry, feed conversion ratio (FCR) or feed conversion rate 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, whereas animals raised for meat – such as beef cows,[1] pigs, chickens, and fish – the output is the mass gained by the animal, the final mass of the animal, or the mass of the dressed output. Specifically FCR is the mass of the input divided by the output. In some sectors feed efficiency, which is the output divided by the input (the inverse of FCR), is used.

## Background

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.[2] FCR is widely used in hog and poultry production, while FE is used more commonly with cattle.[2] Being a ratio the FCR is dimensionless, that is, it is not affected by the units of measurement used to determine the FCR.[3]

FCR a function of the animal's genetics[4] and age,[5] the quality and ingredients of the feed,[5] and the conditions in which the animal is kept,[1][6] and storage and use of the feed by the farmworkers.[7]

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.[8] RFI uses for output the difference between actual intake and predicted intake based on an animal’s body weight, weight gain, and composition.[8][9]

The outputs portion may be calculated based on weight gained, on the whole animal at sale, or on the dressed product; with milk it may be normalized for fat and protein content.[10]

As for the inputs portion, although FCR is commonly calculated using feed dry mass, it is sometimes calculated on an as-fed wet mass basis, (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.[11]

## 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.

### Beef cattle

As of 2013 in the US, a FCR calculated on live weight gain of live-weight gain of 4.5–7.5 was in the normal range with an FCR above 6 being typical.[8] As of 2013 FCRs had not changed much compared to other fields in the prior 30 years, especially compared to poultry which had improved feed efficiency by about 250% since the late 1800s.[8]

### Dairy cattle

The dairy industry traditionally didn't use FCR but in response to increasing concentration in the dairy industry and other livestock operations, the EPA updated its regulations in 2003 controlling manure and other waste releases produced by livestock operators.[12]:11-11 In response the USDA began issuing guidance to dairy farmers about how to control inputs to better minimize manure output and to minimize harmful contents, as well as optimizing milk output.[13] [14]

In the US, the price of milk is based on the protein and fat content, so the FCR is often calculated to take that into account.[15] Using an FCR calculated just on the weight of protein and fat, as of 2011 an FCR of 13 was poor, and an FCR of 8 was very good.[15]

Another method for dealing with pricing based on protein and fat, is using energy-corrected milk (ECM), which adds a factor to normalize assuming certain amounts of fat and protein in a final milk product; that formula is (0.327 X milk pounds) + (12.95 X fat pounds) + (7.2 X protein pounds).[11]

In the dairy industry, feed efficiency (ECM/intake) is often used instead of FCR (intake/ECM); an FE less than 1.3 is considered problematic.[13][11]

FE based simply on the weight of milk is also used; an FE between 1.30 and 1.70 is normal.[10]

### Pigs

As of 2011, pigs used commercially in the UK and Europe had an FCR, calculated using weight gain, of about 1 as piglets and ending about 3 at time of slaughter.[5] As of 2012 in Australia and using dressed weight for the output, a FCR calculated using weight of dressed meant of 4.5 was fair, 4.0 was considered "good", and 3.8, "very good". [16] In the US as of 2012, commercial pigs had FCR calculated using weight gain, of 3.46 for while they weighed between 240 and 250 pounds, 3.65 between 250 and 260 pounds, 3.87 between 260 and 270 lbs, and 4.09 between 280 and 270 lbs. [17]

Because FCR calculated on the basis of weight gained gets worse after pigs mature, as it takes more and more feed to drive growth, countries that have a culture of slaughtering pigs at very high weights, like Japan and Korea, have poor FCR ratios.[5]

### 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,[18][19][20] 5 to 6 on some forages of good quality,[21] and more than 6 on feeds of lesser quality.[22] On a diet of straw, which has a low metabolizable energy concentration, FCR of lambs may be as high as 40.[23] Other things being equal, FCR tends to be higher for older lambs (e.g. 8 months) than younger lambs (e.g. 4 months).[20]

### Poultry

As of 2011 in the US, broiler chickens has an FCR of 1.6 based on body weight gain, and mature in 39 days.[24] At around the same time the FCR based on weight gain for broilers in Brazil was 1.8.[24]

For hens used in egg production in the US, as of 2011 the FCR was about 2, with each hen laying about 330 eggs per year.[24]

From the early 1960s to 2011 in the US broiler growth rates doubled and their FCRs halved, mostly due to improvements in genetics and rapid dissemination of the improved chickens.[24] The improvement in genetics for growing meat created challenges for farmers who breed the chickens that are raised by the broiler industry, as the genetics that cause fast growth decreased reproductive abilities.[25]

### Crickets

Crickets have a low feed conversion ratio of only 1.7.[26]

### Fish

The FIFO ratio (or Fish In - Fish Out ratio) is the feed conversion ratio applied to aquaculture, where the first number is the mass of harvested fish used to feed farmed fish, and the second number is the mass of the resulting farmed fish.[27][28] A ratio of 3:1 would mean that for every kg of fish farmed, 3 kg fish (generally of another, cheaper to produce or capture fish species) is used to farm it.

As of 2015 farm raised Atlantic salmon had a commodified feed supply with four main suppliers, and an FCR of around 1[29] Tilapia is about 1.5,[30] and as of 2013 farmed catfish had a FCR of about 1.[8]

### Rabbits

In India, rabbits raised for meat had an FCR of 2.5 to 3.0 on high grain diet and 3.5 to 4.0 on natural forage diet, without animal-feed grain.[31]

## References

1. Dan Shike, University of Illinois Beef Cattle Feed Efficiency
2. DJ Cottle and WS Pitchford. Production Efficiency. Chapter 18 in Beef Cattle Production and Trade, Ed Lewis Kahn. Csiro Publishing, 2014 ISBN 9780643109896 Pp 439-440
3. Stickney, Robert R. (2009) Aquaculture: An Introductory Text, page 248, CABI, ISBN 9781845935894.
4. Arthur P.F. et al. 2014 Lessons Learnt from 25 Years of Feed Efficiency Research in Australia. Proceedings, 10th World Congress of Genetics Applied to Livestock Production. Abstract here
5. Mike Varley for Pig Progress. Taking control of feed conversion ratio Apr 1, 2009, Last update:Jan 26, 2011
6. National Research Council (Subcommittee on Environmental Stress). 1981. Effect of environment on nutrient requirements of domestic animals. National Academy Press, Washington. 168 pp.
7. Dennis DiPietre for Pig 333. April 21, 2014 Feed Conversion Ratio: critically important but often misused
8. Dan W. Shike, Ph.D., University of Illinois at Urbana-Champaign Driftless Region Beef Conference 2013 Beef Cattle Feed Efficiency
9. Travis D. Maddock, Darren D. Henry, and G. Cliff Lamb. Animal Sciences Department, UF/IFAS Extension. AN217: The Economic Impact of Feed Efficiency in Beef Cattle Original publication date May 2009. Revised October 2015.
10. Robert C. Fry, Atlantic Dairy Management Services. Measuring Feed Efficiency Why & How on the Back of a Napkin
11. Virginia Ishler for Progressive Dairyman. June 30 2014 Calculating feed efficiency
12. Cornell University, University of Wisconsin-Madison, USDA-Agricultural Research Service, Dairy Forage Research Center April 30, 2004 Whole-Farm Nutrient Management on Dairy Farms to Improve Profitability and Reduce Environmental Impacts
13. Michael F. Hutjens August 21, 2012 Feed Efficiency and Its Impact on Feed Intake
14. USDA Natural Resources Conservation Service Conservation Practice Standard: Feed Management: (Animal Units (AUs) Affected): Code 592. September 2011
15. Tony Hall for Eastern Dairy Business September 2011 Define And Improve Your Herd’s Feed Conversion Ratio
16. Department of Agriculture and Fisheries, Queensland Government. Managing a piggery >> Production and performance >> Performance standards Last updated 28 September 2012
17. David R. Stender, Iowa State University Extension. IPIC 25h. Swine Feed Efficiency: Influence of Market Weight 2012
18. Knott, S. A., B. J. Leury, L. J. Cummins, F. D. Brien and F. R. Dunshea. 2003. Relationship between body composition, net feed intake and gross feed conversion efficiency in composite sire line sheep. In: Souffrant, W. B. and C. C. Metges (eds.). Progress in research on energy and protein metabolism. EAAP publ. no. 109. Wageningen
19. Brand, T. S., S. W. P. Cloete and F. Franck. 1991. Wheat-straw as roughage component in finishing diets of growing lambs. S. Afr. J. Anim. Sci 21: 184-188.
20. National Research Council. 2007. Nutrient requirements of small ruminants. National Academies Press. 362 pp.
21. Fahmy, M. H., J. M. Boucher, L. M. Pose, R. Grégoire, G. Butler and J. E. Comeau. 1992. Feed efficiency, carcass characteristics, and sensory quality of lambs, with or without prolific ancestry, fed diets with different protein supplements. J. Anim. Sci. 70: 1365-1374
22. Malik, R. C., M. A. Razzaque, S. Abbas, N. Al-Khozam and S. Sahni. 1996. Feedlot growth and efficiency of three-way cross lambs as affected by genotype, age and diet. Proc. Aust. Soc. Anim. Prod. 21: 251-254.
23. Cronjé. P. B. and E. Weites. 1990. Live mass, carcass and wool growth responses to supplementation of a roughage diet with sources of protein and energy in South African Mutton Merino lambs. S. Afr. J. Anim. Sci. 20: 141-168
24. Peter Best for WATTagnet.com November 24, 2011 Poultry performance improves over past decades
25. Mississippi State University Extension Service Broiler Breeder Management Is No Easy Task, 2013
26. Collavo, A. et al. House cricket small-scale farming. In Ecological implications of minilivestock: potential of insects, rodents, frogs and snails, Ed M.G. Paoletti. CRC Press 2005. ISBN 9781578083398 pp. 519–544.
27. FIFO explanation document
28. FIFO explained
29. Dennis P. DeLong, Thomas M. Losordo and James E. Rakocy Southern Regional Aquaculture Center SRAC Publication No. 282: Tank Culture of Tilapia June 2009
30. Tamilnadu Veterinary Animal Sciences University Extension Service. TNAU Animal Husbandry ::Rabbit No date on website; site accessed June 16, 2016