Prevent misuse of deworming drugs in goat herds with sound parasite control plans

Goats accounted for higher rates of violative drug residues than any other class of livestock in 2010. Goats are more likely to have violations from anthelmintic (deworming) treatment than any other animal health medicines.

The United States National Residue Program for meat, poultry, and egg products is a chemical testing program implemented by the USDA Food Safety Inspection Service. In 2010, the most recent published report, goats accounted for violations at higher rates than any other livestock class. Six of 337 goats exhibited levels of drugs in violation of approved use in the domestic scheduled sampling plan. At 1.78 percent, the violation test rate for goats was 3.7 times higher than any other class of livestock

Avermectins (ivomectin) and milbemycins (cydectin), also known as dewormers or anthelmintics, were the drug classes responsible for all six violations. These related drugs are used to treat parasite infections in livestock. Goats tested specifically for anthelmintics had violation level residues of 1.6 percent and 3.21 percent in 2009 and 2010, respectively.

The suspected cause for the extraordinarily high rate of violations can be attributed to the fact that there are only two drugs currently approved for use in goats (morantel and fenbendazole) and therefore parasites affecting goats are becoming resistant to these drugs. Other anthelmintics can be used for goats under veterinary supervision as “off-label” drug use. Producers are urged to listen to professional advice regarding off label use so as to prevent misuse.

Haemonchus contortus, commonly called barber pole worm, is the most pathogenic internal parasite for small ruminants. Barber pole worm is becoming more resistant to chemicals used to control it, mostly due to overuse of these products and lack of a comprehensive control program. Goat producers can no longer simply try to deworm more frequently with heavier doses. Producers need to develop management practices to control internal parasite infestation that are strategic and well planned.

Michigan State University Extension experts recommend that goat producers develop a veterinarian client patient relationship. Developing a formal relationship allows the veterinarian and producer to work together to develop workable animal health protocols that will aid in better herd health. Some veterinarians may not be fully aware of the parasite resistant challenges that goat farmers are facing. In these instances, incorporating the expertise of qualified professionals into the relationship with the veterinarian is important. Veterinarians and producers can find current information on anthelmintic resistance and parasite control at the American Consortium for Small Ruminant Parasite Control website.

Management practices should include conducting fecal egg counts, FAMACHA, pasture management and other practices directed to managing parasite load. During the process, producers need to be aware of the proper use of deworming chemicals, so as to avoid animals being marketed with violative levels of residues.

Goat producers should only use prescribed or FDA-approved over-the-counter drugs by the recommendation of their veterinarian. All drugs should be used according to label directions. Only a veterinarian can prescribe drugs to be used in an off-label method. Producers need to understand the importance of following instructions regarding dose and administration of health treatment products. Overdosing medicines usually offers no health benefits to the animal. Conversely, under dosing animals can be detrimental to the sound treatment of livestock, especially relating to deworming of goats. Administering less than the directed amount of deworming products frequently leads to poor control of internal parasites and aids in the development of drug resistance. Knowing the weight of the animals to be treated is important for the proper dosing of dewormers.

Drug administration is also critical. Absorption of product into the animal’s blood stream is highly dependent on the route of administration and consequently will create variable withdrawal times. Producers must use health products correctly and responsibly.

Goat farmers should implement an animal health record keeping system that is thorough, yet user friendly. Keeping animal treatment records is a critical step to ensuring that neither milk nor meat is sold before its post-treatment withdrawal time. A key point for a successful animal health record program is the understanding that producers need to use these records to determine withdrawal times. In instances that veterinarians prescribe doses of deworming products above label specifications, withdrawal times need to be extended accordingly.

For more information regarding management of goats for effective parasite control without misuse of deworming drugs, contact Frank Wardynski, ruminant educator at or 906-884-4386, Mike Metzger, small ruminant educator at or 517-788-4292, or Richard Ehrhardt, small ruminant specialist at or 517-353-2906.

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