Controlling environmental mastitis in dairy cows at pasture

Environmental mastitis has traditionally been seen as a problem that occurs during housing. However, time at pasture appears to be a considerable risk period for clinical and environmental mastitis, and increased somatic cell counts for many dairy herds.

The time cows spend at pasture appears to be a considerable risk period for clinical and environmental mastitis, and increased somatic cell counts for many dairy herds. This is often due to exposure to different bacterial pathogens as well as variable environmental conditions.

Where grazing is not adequately rotated, bacteria that cause mastitis can build up in the environment. The areas that can be hotspots of contamination include those where:

• Cows tend to gather
• Cows lie during the night
• Cow traffic is high

Giving some thought to managing these areas, particularly when dividing fields into grazing paddocks, is an important means of controlling the risk of environmental mastitis. This is even more important in wetter summers and where extended grazing techniques are practised.

Wet, dirty areas at pasture are high risk – around feeders and water troughs, under trees, around gateways and cow tracks. Note the areas where cows regularly like to lie. These are likely to include shaded areas on hot summer days, flatter areas in undulating fields and areas just inside gateways.

Avoid having cows on the same pasture, paddock, field or lying area for more than two continuous weeks, and try to avoid returning cows to any one grazing, loafing or rest area for at least four weeks after cattle have used it – unless using short-interval rotational grazing. This is clearly dependent on grazing conditions and grass growth.

Consider actively managing gateways and walkways by using bark, hardcore, or shavings to minimise the risk of poaching and/or change the use of routes and gateways, wherever possible.

Stocking density at pasture

Aim for a stocking density of no more than 100 cows per acre per day in any two-week period.

Fly eggs and larvae thrive in warm, moist organic matter such as undisturbed muck heaps. If you can minimise these fly development sites, it should help reduce the fly populations.

At pasture, a build-up of muck around boundaries and under trees can harbour flies. Don’t overstock these areas or graze for too long, to reduce the risk. To control flies in stored manure, keep it dry and compacted or held in a lagoon at very low dry matter.

Flying insects should be controlled from early on in the fly season. Several products are available based on synthetic pyrethroids such as permethrin and deltamethrin. They can be used as pour-on applied to the backs of animals or as sprays applied as an emulsion via a knapsack sprayer or spray arch. In an average summer, three or four treatments are usually required. Ear tags containing cypermethrin are also available. Most products have zero milk withdrawal requirements and can be used during pregnancy and lactation.

• Clean and renovate areas around feed and water troughs, gateways, tracks and the entrances to the collection yards
• Move water troughs away from gateways
• Check track and gateway placement to avoid wet or poached areas that could lead to cows' udders being splashed
• Wherever possible, rotate gateway use if a field has more than one possible entry/exit point, and design farm tracks to make use of all gateway options
• Adequate drainage, proper design and regular maintenance of cow tracks will reduce problems with dirty teats and udders
• High traffic areas that regularly become muddy could be resurfaced with concrete or other alternative surface material
• Consider fencing off areas that become heavily contaminated and ensure drains and culverts are regularly cleaned out. This can also help reduce the risk of liver fluke
• Where access is required to buildings for water troughs, for milking or for feeding, either rope off cubicles or manage cubicle housing in the same way as during the housing period
• If cows are buffer-fed, it should be done before milking, so that they are more likely to graze directly after milking, giving the teat sphincter time to close before they lie down

If you would like a hard copy of the Cow tracks guide or the Control of environmental mastitis guide please contact publications@ahdb.org.uk or call 0247 799 0069.