According to the current USDA data available in 2008, cull dairy cows accounted for just over 7 percent of all cattle slaughtered in the U.S., but were responsible for approximately 90 percent of carcasses in which drug residues were detected. Some of the more common reasons leading to having a carcass condemned for drug residues include: 1. Changing the dose or route for Procaine Penicillin G: The label dose for PPG is only 1 cc per 100 pounds, or about 15 cc total. When a cow is given higher doses or treated subcutaneously (under the skin), the slaughter withdrawal time can increase from the label four to 10 days up to several weeks.
2. Marketing cows treated for mastitis before completing their slaughter withdrawal: Dairy employees usually do a great job holding out milk from cows treated for mastitis, but sometimes forget that mastitis tubes also have slaughter withdrawal times ranging from four to 28 days.
3. Marketing dry-treated cows before completing their slaughter withdrawal: While it’s tempting to cull a cow who has aborted, she’ll still have residues in her tissues from her dry treatment and a slaughter withdrawal of 14 to 60 days from the day she was dried off.
4. Calves marketed for veal that have consumed colostrum or medicated milk replacer: Calves slaughtered shortly after birth (as bob veal) may have consumed enough antibiotic from the dry-treatment to trigger a positive carcass test. Tissue residues are often caused by calves consuming milk replacer medicated with tetracycline and neomycin. Calves fed medicated milk replacer should never be marketed as veal.
5. Giving pain-relievers in the muscle or under the skin: The only pain-relievers approved for cattle contain flunixin (Banamine, Flu-Nix), a drug which was only designed to be administered in the vein. Giving flunixin-containing products in the muscle or under the skin, rather than intravenously, can increase the withdrawal time from the label four days to more than a month.
6. Marketing cows treated with intrauterine boluses or infusions: Tetracycline can cross the uterine wall and be detected in milk and at slaughter for variable periods. Some veterinary publications recommend slaughter withdrawal of up to four weeks following intrauterine treatment.
7. Thinking there is a “zero meat, zero milk withdrawal” antibiotic: While products containing ceftiofur (Naxcel, Ceftiflex, Excenel, Excede) are attractive because they have no milk withdrawal, all ceftiofur-containing products have slaughter withdrawals ranging from three to 13 days when used according to label. There is no such thing as a “zero meat, zero milk withdrawal” antibiotic.
8. Using any sulfa-drug off-label: The sulfonamide drugs may legally only be used exactly according to label instructions. Recent FDA investigations of residues suggest that overdosing sulfa boluses (Albon) or giving intravenous sulfa products (Di-methox) off-label in the muscle or under the skin has led to tissue residues.
While the situations above are some of the more common causes of tissue residues, virtually any drug can cause residues if it is used off-label or if the drug is used on-label but the label withdrawal isn’t followed.
With the USDA stepping up enforcement on tissue residues and the potential for FDA testing of bulk tank milk in the future, now is an excellent time for dairy managers to review their treatment programs. Your veterinarian can help with information and advice about avoiding tissue and milk residues. PD
References omitted due to space but are available upon request to editor@progressivedairy.com .
—Excerpts from CA Dairy Newsletter Vol. 3, Issue 2, June 2011
