Animal Health

Managing the risk of mastitis in hot weather

By Rod Dyson

TWO RECENT discussions were a reminder of how hot weather can significantly influence the risk of mastitis in dairy herds.

The first was a farm which uses a mechanical teat scrubber as part of the pre-milking routine to clean teats prior to cups on during periods of high risk (both in hot weather and in wet, muddy weather).

The teat scrubber was out of action for four days during a hot spell and this was quickly followed by an outbreak of clinical mastitis.

The second discussion was with another farm inquiring about the need to dry teats prior to applying cups to cows which had been under sprinklers in the yard because of a significant increase in clinical cases during the hot weather.

The two core principles for reducing the risk of mastitis are to minimise the number of bacteria on the teat skin, and to maximise and maintain teat-end health.

During hot weather, groups of cows milling around and also lying in areas of shade will lead to a large amount of faecal contamination in those areas. This creates a marked increase in the risk of teat skin becoming contaminated with dirt and faecal material containing environmental bacteria.

When the teat scrubber failed on the first farm, there was no extra labour available to manage a manual wash and dry program in a single operator herringbone dairy.

Fresh clinical cases of mastitis ceased, occurring shortly after the teat scrubber was repaired and back in use.

On the second farm, milking staff reported a large number of cows entering the milking platform with dirty water running down the teats when the sprinklers were on in the dairy yard.

Sprinklers in the dairy yard are a necessary and effective method of cooling cows, but they also increase the risk of wet, contaminated teats at cups on if the water runs down onto the udder and teats of cows.

While the risk from contaminated water on teats is obvious, applying cups to wet teats also introduces risks associated with cup crawl immediately after cups on.

Clearly, drying those teats prior to cups on will reduce those risks, but if cows are that wet, it is likely that water has continued to trickle down onto teats and into the mouthpiece of the liner while the cows are being milked.

After our discussion, the farm introduced a program of drying teats with paper towel prior to cups on, while they worked on modifying the sprinkler operation.

Obviously, having a strategy to deal with heat stress is extremely important, however each summer we see farms experience a mastitis outbreak during, or immediately after, a heat event.

How can that mastitis risk be reduced, while still managing heat stress effectively?

Naturally shade is essential, but is it possible to reduce the amount of time that cows spend in this area, and/or keep the area cleaner to reduce the build-up of contamination?

Do the cows need to be there overnight when it is cooler? Do they need to be there on days when the heat is not excessive?

Could the area be cleaned? Could feed and water be positioned a short distance away from the shade, so cows will tend to defecate less often in the actual shade area?

Installation of a sprinkler controller or timer so that sprinklers cycle on and off, generally provides more effective cooling, uses less water and significantly reduces the risk of water trickling down onto teats.

Using sprinklers immediately post-milking before teat orifices have closed properly dramatically increases the risk of new infections — washing off teat disinfectant and replacing it with contaminated water is not a good idea, so be very careful with sprinklers shortly after cups off.

One of the biggest opportunities to manage the risk of mastitis is how you manage teat contamination once cows reach the milking platform.

A wash and dry program for at least the contaminated teats, if not all cows, prior to cups on during these hot days will substantially reduce the number of bacteria on the teat skin and consequently the risk of mastitis infections.

In some herds, pre-milking teat disinfection at this time may also be beneficial.

Naturally, these high-risk periods are also when post-milking teat disinfection needs to be as good as it can possibly be all milking staff should concentrate on achieving as close to 100 per cent coverage of teat skin as possible.

For more information, visit Dairy Australia’s Cool Cows website at

-Rod Dyson is a veterinary surgeon and mastitis adviser at