Introduction
Two major health and safety issues surround the antibiotic contamination of milk:
- Products containing antibiotics may cause sensitivity and allergic reactions in humans.
- Regular consumption of milk and dairy products containing low levels of antibiotics may cause bacteria to build up resistance to the antibiotic.
For processors, the quality of the milk supplied directly influences the quality of the end product. As the manufacturing of dairy products such as cheese and yoghurt is dependent on bacterial activity, the presence of any inhibitory substances will interfere with this process and may cause spoilage. In the market place, manufacturers must consistently maintain product quality to maintain contracts and secure new markets. The discovery of drug residues in milk or dairy products will result in contract termination and a tarnished reputation. There are no second chances.
The implications for consumers and processors have a trickle-down effect for producers, in the form of price received for milk. However, more immediate costs to producers include the dumping of and non-payment for contaminated milk.
How do antibiotics end up in the milk vat?
On the farm, antibiotics find their way into milk vats in a number of ways. The most common reasons for failure reported by farmers are:
- Fresh calvers — cows treated with dry cow antibiotics calve early and are milked into the vat before the withholding period has ended.
- Dried off cows — a surprising number of recently treated dried off cows somehow return to the main herd unnoticed by the milkers and are milked into the vat.
- Other antibiotic treatments — most antibiotics have a withholding period. Many enter the bloodstream so footrot treatments and even small injected doses for pinkeye can lead to antibiotic residues in the milk.
- Weekend milking — many violations occur on a Monday because the weekend milker is not aware that one of the cows has been treated with antibiotics and her milk should be withheld from the vat. This may occur because the cow was not identified, the markings were lost, the identification system was not explained clearly or the milker was not paying attention.
- Test bucket overflow — it is not uncommon for the test bucket to overflow during milking. This may occur because the bucket is too small, it is not emptied between cows or it is laid on its side.
All of these failures are preventable. With a reliable identification system and good communication between manager and staff, antibiotics can be kept out of the vat.