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Healthy animals produce healthy food

Antibiotic use in the sheep, goat, and livestock industry

Antibiotics are powerful medicines that are used to fight bacterial infections. Early civilizations used antibiotics in some form or another (e.g. mold), but didn't know how they worked. The earliest discovered and still most widely-used antibiotic is Penicillin.

Sir Alexander Fleming is given credit for "accidently" discovering Penicillin in 1928 [1]. He shared a Nobel Prize in 1945 with the men who developed the technology to mass produce it. Penicillin saved the lives of many Allied soldiers during the Second World War and many lives since.

For more than 40 years, antibiotics approved by the Food and Drug Administration (FDA) have been used to treat sick animals, prevent illness, and maintain the health of animals. Several layers of protection have been put into place to make sure antibiotic use in livestock does not cause harm to humans.

Therapeutic uses of antibiotics by
the sheep and goat industry

Therapeutic use of a drug means that it is being used to treat (sometimes prevent) a disease. Penicillin (many brand names) is probably the most widely used antibiotic in the sheep and goat industry. It is FDA-approved to treat sheep for bacterial pneumonia caused by P. multocida [2]. Slaughter withdrawal is 9 days. Use in goats requires veterinary approval.  Long-acting penicillin is not FDA-approved for sheep or goats and requires veterinary approval.

Naxcel® (Ceftiofur Sodium) is FDA-approved to treat sheep and goats for respiratory disease (pneumonia); however, its use is restricted to veterinarians [2]. There is no slaughter withdrawal [2]. Micotil® (tilmicosin phophate) is another prescription drug that is FDA-approved to treat sheep for pneumonia [2]. Slaughter withdrawal is 28 days [2].

Biosol® (neomycin sulfate) is an over-the-counter drug that is FDA-approved to treat e. coli scours in sheep and goats [2]. Slaughter withdrawal is 2 days for sheep and 3 days for goats [2].
Terramycin® is FDA-approved as an opthalmic ointment for sheep [2].

Though commonly administered to sheep and goats, LA-200® (oxytetracycline), Nuflor® (Florfenicol), Excenel® (ceftiofur hydrochloride), Scour-halt® (spectinomycin), Cefa-Dri® (cephapirin benzathine), and Cefa-Lak® (cephapirin sodium) are not FDA-approved for use in any class of sheep or goats [2]. Use of these drugs constitutes extra-label drug use.

Due to the lack of approved drugs, it is often necessary to treat sheep and especially goats with extra-label drugs.

Sub-therapeutic uses of antibiotics
by the sheep and goat industry

Sub-therapeutic use of a drug is when the drug is administered at a level lower than required to treat disease. The purpose of sub-therapeutic use is to prevent disease. An added benefit has been increased performance by livestock.

Aureomycin® (tetracycline) is FDA-approved for use in growing lambs to increase rate-of-gain and improve feed efficiency [2]. It is commonly included in lamb feed lot rations. There is no slaughter withdrawal [2]. Auromycin® is also approved for breeding sheep to prevent the incidence of abortion caused by Campylobacter fetus infection (vibriosis) [2].

Terramycin® (oxytetracycline) is FDA-approved for use in sheep to increase rate-of-gain and improve feed efficiency by treating bacterial enteritis caused by e.coli and bacterial pneumonia caused by P. multocida. There is a five day slaughter withdrawal [2].

Ionophores are narrowly classified as antibiotics. They have a wide margin of safety. No slaughter withdrawal is required. They are not used in human medicine.


Bovatec® (lasalocid sodium) is an ionophore that is FDA-approved as a coccidiostat for sheep in confinment [2]. Rumensin® (monensin) is FDA-approved as a coccidiostat for goats in confinement [2]. Neither are approved for sheep or goats whose milk will be consumed by people.

It is important to note that ionophores can be toxic to equines. Horses and other equines should never have access to feeds containing ionophores. Because of this, many feed mills that process horse feeds will not process feeds containing ionophores, as they want to prevent accidental contamination.

USDA's new naturally-raised marketing claim allows the use of ionophores, though their use must be disclosed on the product label [3].  Deccox® (Decoquinate) is FDA-approved as a coccidiostat for use in young, non-lactating sheep and goats [2]. It is incorporated into some lamb and kid milk replacers. Deccox® is a quinolone. Unlike ionophores, quinolones are used in human medicine.

Corid (amprolium) can be used as both a preventative and treatment for coccidiosis in sheep and goats [4]. Neither use is approved by FDA. Veterinary advice must be sought we administering Corid to sheep or goats.

Sulfa drugs (sulfamethoxine and sulfamethazine) are also used to treat coccidiosis in sheep and goats [4]. They are not FDA-approved for sheep and goats. Their use constitutes extra-label drug use [5].


Extra label drug use (ELDU)

Extra-label drug use (ELDU) describes the veterinary use of a drug in a manner for which it was not approved. This could mean using the drug for a non-approved species,

giving a higher dose of the drug, or administering a drug in a manner than differs from the label. Extra-label drug use is permitted by veterinarians only. A veterinarian-client-patient relationship is a prerequisite for all extra-label drug use.


Extra-label drug use is essential for minor species, such as sheep and goats, as few drugs are approved for their use and some lack sufficient efficacy to treat specific disease conditions. The alternative to extra-label drug use is to do nothing at all, which compromises the welfare of animals.

But just because a drug is sold over-the-counter (OTC) doesn't mean producers have the right to administer it to their animals without veterinary consent. The misuse of OTC drugs has helped to fuel the antibiotic-ban debate.

Antibiotic use under attack

For many years, the use of antibiotics in animal agricultural has been under intense scrutiny by special interest groups. The Preservation of Antibiotics for Medical Treatment Act of 2009 (S. 619/H.R. 1549) sought to eliminate the "sub-therapeutic" use of antibiotic drugs in livestock [6].

The intent of the bill is to decrease the development of antibiotic-resistant bacteria in humans. Introduced by the late Senator Edward Kennedy, the bill had the support of the president. Advocates for the bill were hoping to include the measure in the legislation to reform health care.

In addition to seeking to ban the use of "sub-therapeutic" antibiotics, in written testimony to the House Rules Committee, Dr. Joshua Sharfstein, principal deputy commissioner of food and drugs, said "farmers should no longer be able to use antibiotics in animals without the supervision of a veterinarian." [6]

Along with most agricultural groups, the American Veterinary Medical Association (AVMA) opposes the bill because it believes it would increase animal disease without assurance of improving human health [7].

While there is some evidence to show that antibiotic use by animal agriculture contributes to the development of antibiotic resistant bacteria, the contribution is considered miniscule compared to the over and misuse of antibiotics in human medicine.

In fact, banning the sub-therapeutic use of antibiotics in animal agriculture may do every little to slow the development of resistant bacteria, but could have many other unintended consequences, such as higher food costs, more pathogens in the food supply, a decline in animal welfare, increased therapeutic use of antibiotics by animal agriculture, and less commitment by the pharmaceutical industry to develop new antibiotics [7]

Feed grade antibiotics are completely banned in Denmark. While there are differing opinions as to the effects of the ban, some sources claim that the ban has increased the therapeutic use of antibiotics, while having no effect on the development of antibiotic-resistant bacteria [8].

It is the opinion of this author that efforts to ban sub-therapeutic antibiotic use and restrict therapeutic antibiotic use in agricultural animals seem to be based more on potential risk and fear than valid data or risk analysis.

Alternatives to antibiotics
There are potential alternatives to antibiotics. Probiotic and prebiotic are the terms given to direct-fed microbial (DFM) products. Direct-fed microbials are products that claim to contain live microorganisms such as bacteria and/or yeast that are thought to aid digestion and digestive tract health.


Enzymes are protein molecules that catalyze specific chemical reactions. Several enzymes have by studied for use as additives in animal feeds.

Our understanding of how and when probiotics, prebiotics, and enzymes improve animal health and performance is in its infancy. Time is needed to conduct the research. Products must also proven to be safe relative to animal, humans, and the environment.

The market is currently littered with products containing DFM and enzyme additives. However, many products contain only trace amounts of the active ingredients and have little or no published data to support an improvement in animal health or importance.

References and further reading

[1] Wikipedia
[2] Animal Drugs @ FDA
[3] Naturally Raised Marketing Claim Standard (January 21, 2009, Federal Register Notice.
[4] Coccidosis in Lambs. Dr. Joe Rook. Michigan State University
[5] Animal Medicinal Drug Use Clarification Act of 1994 (AMDUCA).
[6] Preservation of Antibiotics for Medical Treatment Act of 2009.
[7] The American Veterinary Medical Association Response to the Final Report of the Pew Commission on Industrial Farm Animal Production.
[8] Lessons from the Danish Ban on Feed-Grade Antibiotics. Center for Agricultural and Rural Development. Iowa State University (2003).

This article was written in 2002 by Susan Schoenian.

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