Insufficient withdrawal period
Our milking cow was given antibiotic injections for mastitis and tubed. She has since calved and the withdrawal period has passed but the T101 test continues to show traces of the antibiotic in her milk. What is the point of these withdrawal periods. Who covers the losses I am making?
The withdrawal periods are calculated mathematically on the basis of the average elimination period, adverse effects on humans and whether individual animals or groups of animals are receiving the treatment.
However, the time it takes for drugs to be eliminated will vary from animal to animal. It is determined by giving a group of animals the largest permissible dose. Blood tests are then taken and used to calculate the time it takes for the drug to be eliminated. As the time does vary, an average is used to calculate the withdrawal period. This means that i, on average, it takes four days for antibiotic traces to drop below the permitted levels, it may still take five days in some animals.
Unfortunately, some animals may continue to harbour traces of the antibiotic for an unusually long time. If, in your case, the T101 test has been verified, it is likely that you are dealing with one of these unusual animals. However, it is impossible to apportion blame for the loss of production you are experiencing. Biological processes can be a law unto themselves from time to time.