Why should drug residues be avoided?

Drug residues are very small amounts of antibiotics or other veterinary medicines that can remain in milk and animal tissue for a period of time after an animal has been treated. To keep residues from entering the food supply, milk from treated cows must be withheld from the bulk tank for a specified period to ensure that drug residues are no longer present.

In addition, animals may not be marketed as beef for a certain amount of time after the last treatment.

Why should we be concerned about residues?
Residues in milk and dairy beef are an important food safety issue because some people are severely allergic to certain drugs. Antibiotic residues can also interfere with the production of cultured dairy products and may increase the potential for developing resistance to certain drugs.

Why do residues occur?
Common causes of drug residues in bulk tank milk include:
• Milk from a treated cow in the milking herd was accidentally routed into the bulk tank.
• A dry cow treated with antibiotics was accidentally milked.
• A milking unit was not cleaned properly between treated and untreated cows.
• Purchased cows had been treated and the new owner was unaware of recent treatments.
• One quarter of a cow was treated for mastitis and withheld from the bulk tank; however, milk from the other three quarters was not withheld.
• A drug was used at a higher dosage and/or more frequently than label instructions.
• Medicated feed was accidentally mixed into the lactating cow feed.
• Cows drank from a medicated footbath.

Residues can also be present in edible tissue and organs when insufficient time was allowed between the last treatment and when the animal was marketed.

Mistakes leading to residues in milk and dairy beef include:
• Inadequate treatment records
• Poor identification of treated animals
• Improper use of drugs
• Poor communication between veterinarians, herd managers and farm employees

How can residues affect the dairy?
There are stiff penalties associated with a residue violation, which can result in significant economic losses for a dairy. Bulk tank milk found with residues is dumped, with the dairy producer responsible for the cost of the lost milk.

If a producer markets a cow for beef that is later found to have a drug residue, an inspector will come out to the dairy to identify what led to the residue violation. Repeat residue violators can have their facility quarantined and lose the right to market cows for entry into the food system. Criminal penalties are also possible.

Milk and meat entering the food supply must be safe, nutritious and free of drug residues and other contaminants.  EL