Why are growth promotants used in animal production?

Livestock producers may choose to use what are called “growth promotants” in animals. Growth promotants are used to help increase the efficiency of animal production by increasing weight gain and product output. All growth promotants in the United States have been approved by the Food and Drug Administration (FDA) and have been proven to be safe for human consumption (Gadberry, 2009). There are many different types of growth promotants that livestock producers can use. See the list below to learn more.


Implants are administered through a small pellet that is placed under the skin on the back of an animal’s ear, but some can be given through the animals’ feed (Gadberry, 2009). Implants have been given to beef cattle to increase feed efficiency and daily gains, the amount of weight gained by the animal each day. Feed efficiency is the ability of an animal to better use the nutrients in the feed for growth. Research has also shown that farmers receive ten dollars in profit for every one dollar spent on the implant which helps to increase farm profitability (Gadberry, 2009). The farmers receives this extra profit because of a decrease in feed needed to grow the animal and an increase in market weight of the animal.

How do implants work?

Animal growth is mainly regulated by a part of the brain called the pituitary gland and its secretions of growth hormone (Gadberry, 2009). Implants work by increasing (via the pituitary gland) the amount of growth hormone and insulin in the animal’s cells, which allows the animal to grow more muscle and deposit less fat from the food it eats. This causes a measurable increase in growth rate and improved feed efficiency. Implants don’t guarantee that animals will automatically grow; farmers must still provide the animal with good nutrition (Gadberry, 2009).


Ractopamine is a feed additive that helps to improve weight gain, improve feed efficiency, and increase leanness in pigs and cattle. Leanness means that the animal does not have a large amount of fat in its body. By improving feed efficiency, animals are better able to use food to grow and increase in weight. This means that it takes less time for the animal to reach market weight for slaughter (FDA, 2007). The brand names for ractopamine are Paylean for pigs and Optaflexx in cattle.        


Somatotropin (ST), also known as growth hormone, is a natural protein hormone that is produced by the pituitary gland, which is part of the brain. In dairy cows, bovine somatotropin (bST) is a major regulator of milk production (National Research Council, 1994), (Etherton et al., 1998).  Recombinant bovine somatotropin (rbST) is a man-made version of bST (Raymond et al, 2009). rbST is given to cows by a shot and helps to increase the amount of milk a cow produces. There is no difference between milk that is organic, labeled as rbST free or from cows that received rbST (Vicini et al., 2008). There is no FDA-approved test that can tell the difference between milk from cows given rbST and those not given rbST (Raymond, 2009).

rbST increases milk production by an average of approximately 15 percent in the United States dairy cow population. It also reduces the cost of production of a glass of milk, therefore potentially making milk more affordable for the consumer. The use of rbST to increase milk production in just 15 percent of the U.S. dairy cow population would reduce the carbon footprint of milk production by an amount equal to taking approximately 390,000 cars off the road or planting approximately 290 million trees annually. There is no significant impact on animal health when rbST is used to supplement dairy cattle (Raymond, 2009).


Ionophores (monesin, lasalocid, laidlomycin, salinomycin, narasin) are antimicrobial compounds that are commonly fed to ruminant animals to improve feed efficiency (Callaway et al., 2003). Antimicrobials target the bacteria that live in the animals’ stomachs and alter the bacteria so feed can be better digested. Rumensin is the brand name of monesin and increases milk production efficiency (more milk per pound of feed). Inophores are also used for beef cattle to help increase weight gain and decrease the time it takes to reach market weight.

Subtherapeutic use of antibiotics

Antibiotics are used at low doses in animal feeds as a "growth promotant" and are considered to improve the quality of the product with lower percentage of fat and higher protein content in the meat (Hughes et al., 2002). This is also called "subtherapeutic" use because instead of curing a specific disease, the antibiotics are used to improve overall growth and health.

Growth promotants help to decrease the amount of resources needed to produce food. This ultimately helps to decrease the environmental impact that livestock production has on the world.

Works Cited

Callaway, T. R., Edrington, T. S., Rychlick, J. L., Genovese, K. J., Poole, T. L., Jung, Y. S., Bischoff, K. M., & Anderson, R. C. (2003). Ionophores: Their use as ruminant growth promotants and impact on food safety. Current Issues in Intestinal Microbiology, 4, 43-51.

Etherton, T.D. & Bauman, D.E. Biology of somatotropin in growth and lactation of domestic animals. Physiol. Rev. 1998 Jul;78(3):745-61.

Food and Drug Administration. FDA, (2007). Freedom of information summary: Supplemental new animal drug application. Retrieved from Washington D.C. website: http://www.fda.gov/downloads/AnimalVeterinary/Products/ApprovedAnimalDrugProducts/FOIADrugSummaries/ucm118036.pdf

Gadberry, S. (2009). Growth implants for suckling and growing beef cattle. Arkansas Cooperative Extension, University of Arkanasas, Little Rock, Arkansas. Retrieved from http://www.uaex.edu/Other_Areas/publications/PDF/FSA-3019.pdf

Hughes, P., & Heritage, J. Food and Agriculture Organization, (2002). Antibiotic growth-promoters in food animals. Retrieved from Leeds, U.K. website: http://www.fao.org/DOCREP/ARTICLE/AGRIPPA/555_EN.HTM

National Research Council. Metabolic modifiers – effects on the nutrient requirements of food-producing animals. National Academy Press. Washington, D.C. 1994.

Raymond, R., Bales, C. W., Bauman, D. E., Clemmons, D., Kleinman, R., Lanna, D., Nickerson, S., & Sejrsen, K. (July , 2009). Recombinant bovine somatotropin (rBST): A safety assessment. Paper presented at Joint Annual Meeting, American Dairy Science Association, Canadian Society of Animal Science, and American Society of Animal Science, Montreal Canada. Retrieved from https://www.elanco.us/Content/pdfs/Recombinant_Bovine_Somatotropin_rbST_-_A_Safety_Assessment.pdf

Vicini, J et al. Survey of retail milk composition as affected by label claims regarding farm management practice. J. Am. Diet. Assoc. 2008 Jul;108(7):1198-203.