by Gabe Middleton, DVM
Drug residue avoidance is a critical area for dairy producers to focus on. In today’s dairy industry climate, a milk residue puts the dairy at risk for loss of market access as well as financial losses. In addition, it creates a black eye for the industry in general that all producers certainly want to avoid. On July 1, 2017, the tetracycline screening pilot program will begin, and no less than 1 out of 15 tanker loads of milk will be tested for oxytetracycline, chlortetracycline, and tetracycline. The tolerance limit for the drug is 300 ppb.
Tetracycline products come in many different forms: injectable, powder, and feed-additive. The feed additive products do not apply to this discussion of milk residue testing because these products are not labeled to be added to lactating cow diets, so their use would be illegal under the Veterinary Feed Directive. Oxytetracycline injectable is labeled for the treatment of bacterial pneumonia and infectious bovine keratoconjunctivitis (pinkeye). Extra-label use of oxytetracycline is common, being used for treatment of mastitis, metritis, and topically for the treatment of digital dermatitis (hairy heel warts). Extra-label drug use requires oversight by your veterinarian of record. Drug withdrawals may need to be adjusted when drugs are used in an extra-label manner depending on changes in dose, indication, frequency, or route of administration.
It is common practice for producers, veterinarians, and hoof trimmers to use tetracycline products applied to foot wraps to digital dermatitis lesions. FARAD (Food Animal Drug Residue Avoidance Databank) recommends a 24-hour milk withhold when a cow’s foot is wrapped with the product (powder or injectable). If no milk withhold is observed, this presents a milk residue risk. Another issue that should be monitored is the amount of drug applied to the wrap. More drug creates more risk for residue. Experts have suggested that a 2-gram dose is the maximum that should be applied to a foot wrap. It is not recommended to apply an unmetered amount of drug to the wrap. While tetracycline foot wraps aren’t directly affected by the Veterinary Feed Directive legislation, the powder tetracycline product switched from over-the-counter status to prescription status on Jan. 1, 2017. If the powder product is used, your veterinarian will need to provide the product or write a prescription and they likely place a milk withhold on the label. It is critical for the producer to obey this withhold.
As with any drug residue prevention program, the size of your herd shouldn’t affect the withhold of the product. Obviously smaller herds have much less room for error when it comes to drug residues in milk, however, the dilution factor is not a justification for reduction of milk withholds. The integrity of dairy products relies on proper drug use and withholding.
Antibiotic use is under more scrutiny than ever for many reasons. Dairy producers should view the tetracycline testing pilot program as an opportunity to renew their commitment to disease prevention and lameness reduction. Dairy managers and veterinarians should review footbath protocols to make sure the proper concentration of an effective product is being used, proper number of cow passes is being monitored, and frequency of footbath application is adequate. Heifer facilities are often overlooked when it comes to digital dermatitis prevention. If heifers have a hairy heel wart prior to calving they are much more likely to have a recurrence during lactation. Cleanliness alone goes a long way to prevent digital dermatitis in heifers. If your pre-calving heifers are affected with digital dermatitis, you need to develop a plan to treat and prevent the lesions in that group as well as lactating cows.
Antibiotic use needs to be transparent on dairy farms and this program is another way for the dairy industry to prove to the public that products are safe. As long as the tetracycline class of drugs, and all drugs for that matter, are used properly, the dairy industry will have nothing to hide. If we aren’t able to assure the public on the safety of dairy products, niche markets will increasingly fill those needs.
Gabe Middleton is a partner at Orrville Veterinary Clinic in Orrville, Ohio. He can be contacted at firstname.lastname@example.org