News

Managing Milk Hygiene at Grazing

Published 12 May 09

DairyCo extension officer Hugh Black looks at the costs and causes of environmental mastitis.

Mastitis costs the average 100 cow herd £12,000 per year for clinical cases alone, but added into this are the additional losses from effects such as SCC penalties, yield loss and secondary health effects. Environmental mastitis appears to be an increasing problem on many dairy farms, and rising cell counts are often a particular problem throughout the summer period.  Recent figures from Northern Ireland show that in July, August and September twice the number of milk samples sent for bacteriology contain the pathogen Streptococcus uberis (Strep.uberis) when compared to other months.

There are a number of reasons for the increased incidence at this time of year.  But one of the main causes is the build up of pathogens, particularly Strep.uberis, but also E.coli, in the grazing environment and in areas where cows tend to gather, and this can often be overlooked on farm. One report from the US has shown that a high proportion of soil and herbage samples can become contaminated with Strep.uberis.  The study revealed that lying areas, and gathering or traffic areas were particularly prone to contamination. 

"Throughout the year, almost 90% of samples from outdoor lying and gathering areas tested positive for presence of Strep.uberis, as did 42% of water samples. Two-thirds of samples from grazing areas tested positive for Strep.uberis in the pasture season." R.N.Zadoks et al. / Veterinary Microbiology 109 (2005)

The main problem for farmers is that it is so difficult to control where cows lie down.  Cows tend to lie in the same areas, which soon become contaminated with environmental mastitis causing pathogens.  For example, shaded areas on hot days, the level areas of undulating fields, and areas just inside gateways after a long walk are all problem areas.

Take a look at these preferred areas and try to discourage cows from lying down with the use of electric fencing.   Manage water troughs, gateways and tracks carefully to avoid poaching and standing water that could splash cows' udders. Managing stocking rates is one of the best ways to try to control mastitis.  Overall I would recommend no more than two weeks on a grazing or loafing area followed by a four week rest.  A maximum of 100 cows per acre in the two week period, for example, 100 cows for one day before moving on and resting the area, or just over seven cows per acre for 14 days before moving on and giving the area a rest. 

If cows need access to buildings during milking or feeding and can't be shut away from cubicle housing, either rope off cubicles or manage them as you would during the housing period.  It is also worth considering buffer feeding before milking to encourage cows to graze post milking before lying down. Many cases of mastitis in early lactation arise from infection during the dry period.  If more than one in 12 cows get mastitis in the first 30 days of lactation this indicates a dry period infection problem.  

Using a single loafing paddock close to farm buildings for dry cows also leads to a build up of pathogens.  Rotate the paddocks, giving cows no more than two weeks in each, then give the area four weeks rest.  In this situation I would recommend a maximum stocking rate of just over seven cows per acre. Sand yards are one option when managing the outside environment is difficult.  Sand is more inert to bugs, so will not become infected to the same extent.  You will need to maintain it by scooping the manure off twice a day though.

Nutritional advice for pre-calving is to keep cows tightly stocked on restricted grazing.  But this will render the area prone to a build up of pathogens, making mastitis control a serious challenge.  Again, rotate the area with a maximum stocking rate of just over seven cows per acre and aim for no more than two weeks in the paddock, and then four weeks rest. 

Finally, sample clinical cases for bacteriology, as it is essential to know what bugs you're dealing with. DairyCo's Mastitis Control Plan has launched this spring to vets and consultants across the UK.