BOAH: Dairy Drug Residue Information

What is a Residue?

Drug residues result when a drug or its metabolite is detected above the legal limit in a food product. Residues can occur in milk, meat (tissue), honey or eggs. Milk residues are detected at the processing plant when milk from each tanker load of milk is tested before it is unloaded. Tanker trucks can contain milk picked up from one large farm or may contain co-mingled milk from multiple small farms. Regular milk quality samples from dairy farms are also tested for residues at the lab on a regular basis. The food product containing a residue is considered contaminated by the FDA and must be removed from the human food supply.

Why do milk drug residues occur?

There are many different reasons a milk residue can occur, but they generally fall into one of the four categories listed below.

Milking a treated cow:
A dry cow escapes the dry pen and gets back in milking herd but was not marked as treated and is accidentally milked.
The milker forgets to put a band or paint mark on a treated cow, and she is milked at the next milking.
A family member who doesn’t usually milk fills in for a milking shift but isn’t trained properly and doesn’t realize cows have been treated.

Improper cleaning:
A treated cow is milked into a bucket, but the claw and teat cup are not rinsed before using the equipment for the milking herd.
The weigh jar and milk hose are not rinsed properly after milking a treated cow.
A treated cow is milked into a bucket and bucket is used on the rest of the herd without rinsing.

Equipment:
The overflow bucket used to milk a treated cow overflows into pipeline.
A long milk hose still has treated cow milk in it when used to milk the rest of the herd.

Improper drug use:
Intramammary infusion of unapproved drug occurs.
Labeled withdrawal time for drug is not followed.
Extra label drug use without veterinary oversight results in longer withdrawal time than the label states.

What happens when a drug residue occurs?

The farm with a drug residue is notified as soon as the residue is detected. Milk cannot be used for human consumption from that farm until another milk sample tests negative for drug residues. The farm also receives a letter from BOAH, and a fine may be imposed based on the amount of milk shipped. The positive farm is responsible for the cost of all the milk on the tanker truck that is not theirs.

The farm owner must have a meeting on the farm with a BOAH veterinary epidemiologist and the farm’s private veterinarian to discuss the milk residue and residue prevention practices on the farm. A second residue within 12 months results in a meeting at the BOAH office and an additional fine. A third residue in 12 months would result in the loss of the farm’s milk license.

How can milk residues be prevented?

Follow withdrawal times for all drugs. Talk to your veterinarian with any questions about withdrawal times.
Keep records of all drug treatments for at least two years.
Train all family members and employees who will be milking or treating cows. Training should include proper milking technique, correct treatment procedures, and drug residue prevention.
Milk treated cows last or clean equipment thoroughly after milking a treated cow.
Don’t put off marking a treated cow or recording treatments. Do these when treating a cow so you don’t forget.
Mark dry cows as treated even if they are moved to a separate pen or separate location after receiving treatment.
Pay attention. Most residues are caused by human error and are preventable.