April 18, 2018

Food Safety

Violative Antibiotic Tissue Residues at Slaughter: Sorting Out Who, What and Why

Dr. Bruce Sherman, DVM, MPH, Bureau of Regulatory Services

Most livestock producers are well aware of the importance of having a comprehensive herd health plan developed with their veterinarian that includes the responsible use of antibiotics, now often termed “antibiotic or antimicrobial stewardship,” primarily as a means of preventing residues from such drugs contaminating or adulterating animal-derived food products. 

In addition, the emerging crisis of antibiotic resistance, contributed in large part to their overuse, is driving the movement toward enhanced antibiotic stewardship in both veterinary and human medicine and has led to further regulatory controls.        


One such control program is testing tissue (meat) at slaughter for antibiotic residues.  Producers may not have a good understanding of this program because of the different roles of various agencies that are seldom explained. 

USDA’s Food Safety and Inspection Service (FSIS) oversees the Federal Meat Inspection Act. This act ensures animals are examined before slaughter, humane methods of slaughter are used, and the carcass is examined after being harvested.

The animal’s identification and samples are collected and analyzed before the carcass enters the food chain in order to protect the public from exposure to harmful levels of chemical residues in meat, poultry, and egg products.

Drug residues are any component present in edible tissues after treatment of a parent drug or a metabolite of any drug. Although this article focuses on livestock only, edible tissues include muscle, kidney, fat, skin, milk, egg, or honey.  FSIS enters violative information into the U.S. Food and Drug Administration (FDA) database and also reports the information to the states.

When a violative sample is at or above a designated threshold, FDA conducts an investigation.  FDA’s Center for Veterinary Medicine (CVM) is designated to regulate medications given to food animals and to issue enforcement actions.

CVM utilizes a risk scoring system for drug residues that incorporates contributing factors such as the level of exposure, the toxicity of the residue, and the frequency of past violations by the producer or firm in assessing fines or other possible enforcement actions.

These residues are of concern due to the adverse health effects that they can cause in humans, such as an increase in resistant microorganisms, allergic reactions, and acute or chronic effects from consuming such chemicals.

Residue levels are categorized into three levels of concern. The first level is a drug not approved for use in any animal. The second is a drug that was found in an unapproved species or class. The third is a drug found in an approved species or class however, the residue level exceeds the limit.

The FDA investigation will trace back to the source(s) that may have caused the illegal residue.  It will involve the review of the farms in-place drug residue avoidance system. 

This will include determining if the farm maintains a documented drug inventory, if there is a prescribing veterinarian of record, and if complete treatment records along with proper animal identification are maintained.

Certain management practices will be assessed, such as segregating treated animals, discarding colostrum from treated cows, as well as drug dosage, duration, frequency, route of administration, withdrawal times for meat, and milk, etc.

Over the past five years, Connecticut has had tissue residue violations in 15 adult cattle and 20 calves out of all of the dairy and beef animals sent to USDA inspected slaughter establishments.

Often times these violation investigations have incorrectly identified the origin/source of the treated animal due to a compromised chain of custody.  These animals can change custody two to four times in the days that follow the animal leaving the farm, prior to harvest. 

In a number of instances, the Department of Agriculture (DoAg)’s Bureau of Regulatory Services has relied on its Animal Disease Traceability data bases to assist FSIS, FDA, and producers in successfully identifying the true farm of origin responsible for a violative tissue residue and thus avoiding penalizing the wrong farm. 

DoAg routinely monitors violative tissue residue information provided by FSIS and FDA and contacts those producers in violation—especially in the case of repeat violators. USDA requires that all dairy cattle/calves of any age be officially identified prior to the first point of comingling such as on transport vehicles or livestock sales barns. 

Producers should make sure their receipts and/or their owner/shipper statements include each animal’s complete identification number.  This practice will help avoid an animal with a violative tissue residue being traced to the incorrect farm.  

As part of this system, producers need to include a documented chain-of-custody for every animal that leaves their farm, which records the animal’s complete official identification number, description of the animal, date, a signed statement declaring the animal’s treatment status (even if there is none), hauler’s name, and the final intended destination of the animal(s).  

Any live animal raised for food or intended to be offered for slaughter is considered food.  A food animal in interstate commerce that is considered adulterated or misbranded is cause for legal action.

In summary, a visit to your farm from an FDA investigator and/or a levied fine, both as a result of a violative tissue residue, will not likely be pleasant experiences, so practice good antibiotic stewardship, taking all the recommended and necessary steps of prevention.

DoAg’s Bureau of Regulatory Services previously mailed the National Milk Producers Federation (NMPF) Milk and Dairy Beef Drug Residue Prevention 2017 Reference Manual to all Connecticut licensed dairy farms.

The following organizations have information available on steps producers can take to ensure the judicious use of antibiotics and, if warranted, have the proper procedures and documentation in place in case of a violative tissue residue:


Or contact the NMPF

(703) 243-6111



Or contact Food Armor at

(603) 257-3665