John H. Kirk, DVM, MPVM
Veterinary Medicine Extension
School of Veterinary Medicine
University of California Davis, Tulare

In a recent Dairy Today issue (October 2001), there was a very complete listing of reasons for antibiotic residues in milk and meat of dairy cows. Almost every situation was mentioned that might result in a residue. Here is a list of the reasons that seem to apply particularly to our western dairy herds.

There is no argument that these situations actually happen and result in residues to both milk and meat. However, the root of the problem is deeper than this. These seem to be merely symptoms of the root problems. Here are some of the underlying problems leading to these reasons for residues:

1. The herdsmen or persons in charge of treating cows are not working closely with their herd veterinarian to maintain a current plan for treatments. There should be a written protocol for each treatment listing the signs of the disease or condition to be treated, what drug(s) should be used, how much should be given and by what route, how often should it be repeated and the maximum number of treatments, and the milk and meat withdrawal times. All this should be written out in great detail leaving no doubt as to what must be done each and every time. There should also be a written treatment record or computerized record where each treatment will be recorded and the withdrawal dates calculated. The written records should be monitored periodically to detect shifts or drift in the treatments made by workers and to determine the effectiveness of the treatments. Feedback from the workers is important to make sure the treatment protocols are practical and workable on the dairy.
2. Lack of a continuing, routine training program for new and experienced employees is another underlying cause of residues. The herdsmen and veterinarians should be actively involved in worker training. Each worker that is allowed to treat animals should be required to attend, as a term of his or her employment. Workers should be trained in the treatment protocols and how to enter treatments into the records. The workers should get a short course in recognition of the common diseases they may encounter on the dairy.
3. A very limited number of well-trained employees should be allowed to treat animals. When lots of workers treat cows, invariably multiple treatments result, leading to residues. The fewer treaters there are, the better for most dairies. If possible, only one person should do all the antibiotic treatments. Each of these workers must attended the training sessions and be very familiar with the treatment protocols. Each person who is allowed to treat animals with antibiotics should know how to read drug labels and calculate the appropriate dose.
4. Once the veterinarian and dairy herdsmen develop a treatment protocol for the common diseases they have on the dairy, it will not be necessary to use extra-label treatments except in rare situations. If they are used more than occasionally, they can be defined in the treatment records. By avoiding extra-label treatments, much of the doubt about withdrawal times can be removed.

In summary, there are many reasons why residues occur as noted in the Dairy Today article. In reality, however, these are only symptoms of the true problem. Lack of written treatment protocols and record keeping systems, inadequate employee training, too many workers treating cows and extra-label treatments are the true problems. By dealing with these issues, residues can be avoided.