Reducing The Risk Of Mastitis During The Grazing Period
15 May 2025Mastitis is traditionally seen as a problem during the housing period when there is higher risk of infection. However, there is a risk of environmental and clinical mastitis occurring during the grazing period and increased levels of somatic cell counts can be seen during this time. There are a number of ways of reducing the risk during the grazing season with the top factor being ensuring adequate rotation during grazing and maintaining areas which are at a higher opportunity of becoming poached like tracks and gateways.
Mastitis At Pasture
Dairy cows are at risk of environmental and clinical mastitis at pasture due to the presence of different bacterial pathogens from the housed environment and variable environmental conditions. Within the field, there are certain areas which pose a higher risk due to the build-up of bacteria. These include areas of high cow traffic, gathering places of cows and where cows lie during the night. The wet, dirty areas of the field, particularly around water troughs and gateways can increase exposure to pathogens, so it is important to determine whether there are ways to reduce cow traffic in these areas. Ensuring fields are adequately grazed in rotation will reduce the risk of mastitis as cows will not be spending significant periods of time in these areas.
Maintain High-Traffic Areas
Areas of high traffic like trackways to and from the milking parlour should be maintained regularly to avoid poaching and splash back on to the udders. Consider options of how to minimise trackways becoming poached, for example, using bark or hardcore in gateways which are used every day. For tracks which are used regularly throughout the grazing period, consider whether there is an opportunity to upgrade them. There are a variety of different surfaces which can be used including hardcore, woodchip/bark or artificial turf. Maintenance and adequate drainage on the tracks are important to reduce poaching and therefore reduce the likelihood of dirty teats and udders. Further benefits on hoof health and less lameness may also be seen.
Fly Control
Fly control is a key consideration during the grazing period, as typically fly eggs and larvae thrive in warm, moist areas like a midden or dung heaps. Avoiding having middens or dung heaps close to or in the grazing fields is a way of minimising the opportunity for flies to develop and grow near the herd. Build-up of muck along tracks, boundaries and under trees can provide ideal habitats for fly eggs to be laid and develop. Similarly, fields which have a lot of tree cover providing shade and shelter for cows is also a great habitat for flies. Dry cows and in-calf heifers tend to be at a higher risk of summer mastitis due to these animals remaining in the same field in the lead up to calving, so it is important to consider whether the field has areas which are particularly suitable for fly populations to thrive in. Later into the grazing season, it is advisable to top the fields to remove tall weeds and old seed heads which provide cover for the flies.
There are different methods which can be used to help prevent mastitis from flies through a variety of pour-on products which typically are applied down the back of the cow and give cover for various lengths of time. It is important to check the product to determine as and when it will need to be re-applied to ensure the cow has sufficient cover during the grazing period. It is also important to check whether the product has any withdrawal period for meat and milk as this can vary with different products. Ear tags which contain the insecticide, cypermethrin, can be used and will provide cover throughout the grazing season.
Dr Cara Campbell, SAC Consulting
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