News

The winter's nearly here.  Our local mastitis lab, Bridgelands Laboratory in Midhurst has been a little quiet in the last few weeks, with a few days of autumn sunshine to keep everything dry.

But, now the cows will be coming in again, we can expect things to hot up a little.  Environmental mastitis is recognised as the major challenge to improving milk hygiene and quality.  Much research and scientific application has taken place, yet still the average cell count in UK herds remains at nearly 200 000, and the national average clinical mastitis rate is deteriorating.  Figures from labs all over the UK, including our own local laboratory findings, indicate an overwhelming incidence of the main environmental pathogens, namely E. coli and Strep. uberis.

E coli, and other members of the coliform family, are a universal occurrence on all farms.  Each teaspoon of cow poo contains billions of them and it only takes a dozen or so to cause a case of mastitis.  The severity of illness can vary widely, which depends on the pathogenicity of the bug (ie its own ability to cause the release of bacterial toxins) and the health of the cow.  Sometimes we see just a mild illness, perhaps with no clinical signs at all, yet other cows may be desperately ill, and can die within hours of infection. 

Strep. uberis is a slightly different kettle of fish.  Many cows carry the bug as a normal inhabitant of their bodies, on skin, on their tonsils, in their reproductive tracts.  The problem arises when the environment becomes seeded with the bug, which is kind of inevitable really!  An environment where there is a suitable growth medium, warmth to grow, plenty of moisture, will allow the strep to multiply and flourish.  A nice moist straw bed, perhaps the straw wasn't the best ever, add a bit of urine, composting nicely to give a comfortable surface temperature, is just ideal.  We've even seen a few incidences over the summer, at grass in warm weather, where cows have favoured a particular area, that area has become heavily polluted with bacteria, and a high mastitis risk ensues.  We also have the difficult situation that Strep uberis has many variants, or strains.  Some of these strains are harmless, others may be very well "cow-adapted", resulting in chronic infections which are very hard to cure, and which may then be spread from cow to cow at milking time.

So, now we've established that the cow's environment is a potential source of mastitis bacteria, we need to think about how to keep that environment out of the cow's udder.  There is only one way in which nasty bacteria can get into the udder to cause mastitis, and that is through the end of the cow's teat.  With that fact in mind, we then have to consider just how severe is the level of exposure to bacteria, ie just how dirty are the cow's surroundings, and how dirty are her teats?  Secondly, how can we influence the cow's own defences?

The first port of call is the dry period and calving time.  Most mastitis cases occur in the first month of calving.  Most of those cases will be due to bacteria picked up during the dry period, when the cow is having a break from being milked, before calving.  Internal teat sealants, put into the teats when the cow stops milking, have made a massive improvement in early lactation mastitis rates, indeed I am firmly of the opinion that no dairy cow should be denied them, but they aren't a total solution.  Dry cows are often the unfortunate forgotten herd, stuck in a field up to their knees in mud, or in inadequate housing.  They need a clean, dry environment just as much as anyone else.  Good, comfortable calving accommodation, where the cow can go through her instinctive natural behaviour when giving birth, yet can still be observed and helped if trouble ensues, is a must on any farm.

So, she's calved, she's in the milking herd, everything's OK so far.  What needs thinking about next?  Increasing numbers of any animals, and keeping them in prolonged contact with their own waste products, is a potential high disease risk.  Yet the market pressure that dairy farmers are under is causing this fundamental fact to become an increasing issue.  Spreading overheads by pushing the cow numbers up, trying to economise on bedding, in a year when straw is very short and often poor quality, trying to keep labour costs down, being unable to invest in building improvements:  these are all resulting in greater exposure of cows to environmental mastitis pathogens.

What can our dairy farmers do?  It's the basics really: good control of slurry; clean concrete; well maintained tracks to keep feet, legs and udders clean in the first place.  Cows should be exposed to "minimal stress" in their lives (just like farmers and vets!). When cows are in the parlour, it's good teat cleaning and pre-milking procedures, to ensure hygienic milking, good mastitis detection and prompt treatment of affected cows: these are the things that make the difference.  A well-maintained milking machine, to reduce the risk of compromising the cow's own defences, should be without question.

If any dairy companies are out there listening, these things are achievable, but it comes at a cost.  Too many of our dairy farms are standing on a knife edge of profitability and if we want a quality, welfare-friendly, local product to still be available in years to come, it has to be paid for properly, and fairly, and now!

Keith Baxter BVetMed MRCVS

This article appears in the December issue of South East Farmer