Veterinary Warning Letters

Letter Highlights FDA’s Role in Protecting the Food Supply from Excessive Drug Residues

When most people think about food safety inspections at slaughterhouses, they think of the U.S. Department of Agriculture. Few realize that the U.S. Food and Drug Administration also plays a critical role in protecting the nation’s food supply from unsafe animal drug residues.

A recent warning letter issued by FDA’s Center for Veterinary Medicine (CVM) illustrates how federal agencies work together to ensure that meat entering the food supply complies with federal safety standards. The warning letter cites Allandale Dairy of Pierz, Minnesota, following USDA laboratory testing that detected illegal drug residues in the liver of a dairy cow offered for slaughter.

Illegal drug residue level detected

According to the communication, USDA’s Food Safety and Inspection Service (FSIS) collected tissue samples from a slaughtered dairy cow after it was sold through auction. Laboratory analysis detected sulfadimethoxine in liver tissue at 0.116 parts per million, exceeding FDA’s established tolerance of 0.100 parts per million for edible cattle tissue.

Sulfadimethoxine is a sulfonamide antibiotic used in cattle and other livestock to treat certain bacterial infections, including respiratory disease, foot rot, and other susceptible infections. Like other veterinary antibiotics, it is an important tool for maintaining animal health when used according to approved labeling or under lawful veterinary supervision.

Sulfadimethoxine can remain in edible tissues for a period after treatment, so FDA has established maximum residue tolerances and required withdrawal periods. These requirements are intended to ensure that meat entering the food supply contains drug residues at levels determined to be safe for consumers.

Because the residue exceeded the legal tolerance established by FDA, the meat was considered adulterated under the Federal Food, Drug, and Cosmetic Act.

More than a single animal

FDA’s concerns extended beyond the individual animal. During its inspection of the dairy operation, investigators concluded that treatment records were incomplete and failed to consistently document medical conditions treated, routes of administration, and individuals administering medications.

FDA stated that these deficiencies increased the likelihood that medicated animals bearing potentially harmful drug residues could enter the food supply.

Accurate treatment records are essential because they help producers observe required withdrawal periods before animals enter the food chain.

Extralabel drug use

The warning letter also identified concerns regarding extralabel drug use. FDA alleged that sulfadimethoxine and flunixin meglumine were administered in ways that differed from both approved labeling and veterinary prescriptions, including dosing inconsistencies and treatment schedules that exceeded approved directions.

Federal regulations allow certain extralabel uses of approved animal drugs under veterinary supervision, provided specific requirements are met. The agency concluded that the uses identified during its inspection did not comply with those requirements and therefore rendered the drugs unsafe under the Federal Food, Drug, and Cosmetic Act.

Why residue monitoring matters

Drug withdrawal periods exist to allow medications administered to food-producing animals to decline below established safety limits before meat or milk enters commerce. Residue monitoring programs help verify that these safeguards are working.

When violative levels of residues are detected, FDA investigates whether they resulted from inappropriate dosing, inadequate recordkeeping, failure to observe withdrawal periods, or broader deficiencies in herd management practices.

Regulatory implications

Although this warning letter concerns a single dairy operation, it highlights several broader regulatory principles applicable to food animal producers.

They include maintaining complete and accurate treatment records, following approved labeling or lawful veterinary directions, using animal weights to calculate appropriate drug dosages, observing required withdrawal periods before marketing animals for slaughter, and maintaining management systems that prevent animals with violative drug residues from entering the food supply.

Failure in any one of these areas can result in adulterated food entering interstate commerce and trigger FDA enforcement action.

MDP perspective

This warning letter illustrates that FDA’s Center for Veterinary Medicine regulates much more than companion animal drugs. Its oversight extends throughout the food production system, from veterinary drug approvals and lawful drug use to residue monitoring, recordkeeping, and the protection of consumers.

Equally important, the case demonstrates the complementary roles of FDA and USDA. USDA identified the violative residue through slaughter surveillance. FDA then investigated the on-farm practices that allowed the residue to occur and evaluated compliance with federal animal drug regulations.

Together, the agencies form an important safeguard designed to ensure that food derived from treated animals meets established safety standards before reaching consumers.