There is nothing more frustrating than going to the trouble of taking a milk sample from a mastitis cow, culturing it (either on farm, with the Overnighter, or at through our lab) and having it return as a contaminated sample.
“Contaminated sample” means that the microbes that have been grown are not typical or recognised causes of mastitis, and are therefore unlikely to be the cause of a clinical case. Usually the bugs grown are typical of those that live in the gut (and pass out in the dung) of cattle. Most commonly they are there by accident (the sample not having been taken adequately, or, more rarely, because these bugs have somehow managed to colonise the udder and cause mastitis.
Here are some tips to help you take a sterile sample:
1. Do not wash the udder. Water dripping down and off the teats will contaminate the sample with bugs from the udder skin.
2. Use a clean new specimen pottle – not one that has been lying around for years, and not a vegemite jar! Always have a few pottles in the milk room ready for this job.
3. Use teat wipes to thoroughly disinfect the end of the teat – as you would for dry cow therapy.
4. Wash your hands, or put on a pair of clean milking gloves.
5. Take the lid off the pottle, making sure the inside of the lid always faces down (so that no muck can fall onto the inside surface). Do not put it on the ground. I do this by holding the pottle in my right hand, and holding the lid between the little finger and the side of my left hand, as I unscrew it. Then I transfer the pottle to my left hand, and hold it between my left forefinger and thumb.
6. Hold the pottle on a 45o angle, again to reduce the area that muck can fall in to.
7. Strip three or four squirts of milk onto the concrete.
8. Keeping the pottle well away from the teat end and the cow, fire a squirt of milk in. A teaspoon of milk is all that is required. Overfilling pottles is one of the main causes of contamination.
9. Put the lid on immediately, label the pottle with cow number, quarter and date. Chill (if sending for analysis) or freeze for later reference.
10. Treat the cow.
As a routine measure, milk samples should be taken from all mastitis cases before any treatment is given, and samples frozen (for up to a month). A pool of samples is thus available if and when a problem may arise (high incidence, or poor response to treatment).
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