Let us spray!
Sanitising teats after milking has always been a fundamental and widely accepted strategy for mastitis control.

The rationale is very simple: if a zero population of bacteria on the teat can be maintained it is impossible for the cow to develop a new intramammary infection.

However, the world is less than perfect, and in reality, zero bacteria on teat skin cannot be achieved or sustained. Bacteria from other cows or from the cow environment readily contaminate teat skin, even on an hour-to-hour basis. The key point is that it is a "numbers game", and the lower the average population of bacteria that management practice can achieve on the teat, the lower the probability of an infection developing.

Skin condition

Applying a sanitiser to the teats not only kills bacteria resident on the skin, it also keeps the teat skin in good condition, free of cracks and cuts that will harbour and provide growth sites for bacteria.

When teat skin dries out due to mud or wind, it can become very rough and may develop cracks, which entrap faecal and soil material that provide a nutrient reservoir for bacteria. For this reason, sanitisers contain an emollient to maintain skin moisture levels and prevent chapping and cracking.

Testing sanitisers

The outright bacterial killing power of the sanitiser is a key factor. For some time now, Dexcel has provided the dairy industry with a standard test of teat sanitiser effectiveness.

Under laboratory conditions, teats (acquired from meat processing plants) are immersed in a solution containing mastitis bacteria. For one group of teats the test sanitiser is applied, for a control group no sanitiser is applied. Teats are left for 10 minutes to allow the sanitiser to kill bacteria, and then are rinsed. The bacteria in the rinsings from teats that had the sanitiser applied are counted and compared with the bacteria count of the rinsings from the control teats.

Many sanitisers sold in New Zealand have been put through this test. To pass, the sanitiser must achieve a 1000-fold reduction in the number of bacteria rinsed from the skin when compared with the undipped control group. If a sanitiser does not work in this lab test, it is most unlikely to work in the field.

Teat sanitisers that have passed this test carry the words "Passed Protocol A 1997". Look for them when you buy.

Spray or dip?

Having established that you are using a product that efficiently kills mastitis bacteria, the next most important part of the control process is to make sure you apply it to the teat skin with good coverage.

In most countries this is achieved by dipping the teat in the sanitiser. In New Zealand we are paranoid about economies of time, so we have adopted the faster method of teat spraying. Spray application often does a bad job, and certainly much money is wasted by not achieving coverage on the teats.

Numerous experiments internationally have shown that teat dipping with a sanitiser reduces new mastitis infections (typically by 50%). But very little research has been carried out in New Zealand using spray application and also relating to the different set of bacteria that cause mastitis in New Zealand.

It should also be noted that the laborator,v test of sanitiser effectiveness as described above, involves dipping in the sanitiser, not spray application.

Teat spraying DOES work!

A recent Dexcel field experiment looked at the impact of teat spraying with sanitiser after milking on new mastitis infections and teat skin condition.

This study involved about 500 trial cows within five herds. One cow group did not receive teat sanitising, the other did, the study being over a whole season. The sanitiser used was an iodine-based formulation that had passed the Protocol A test. It included 9% emolient, and was used at a 1:4 dilution throughout the full-lactation.

Results showed reductions in new mastitis infections for the sanitised group, for all types of mastitis bacteria. In the case of the major mastitis pathogens, Strep. uberis infections were reduced by 72% and Staph. aureus infections by 55%. The reduction of Strep. uberis cases is particularly significant for New Zealand herds since this is our major mastitis problem. Teat skin abnormalities involving cracks, cuts and chapping, were reduced by at least 54% for those teats that were sprayed.

A very effective weapon

Teat spraying with an effective sanitiser over a whole lactation reduces new mastitis cases by at least 50% and achieves a similar reduction in teat skin abnormalities.

Murray Woolford
Dexcel Research

Reproduced with kind permission of New Zealand Dairy Exporter

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email: jim@pcfarm.net