By Kathryn Hume BVM BVS MRCVS, Ashford Practice
Mastitis is inflammation of the udder and is a major disease seen in dairy cattle. Environmental mastitis is an intra-mammary infection of the udder originating from bacteria in the cow’s environment. Some common bacteria found in the cow’s environment which can cause mastitis include, Streptococcus uberis, Escheria coli and Klebsiella. The occurrence of environmental mastitis is dependent on the level of exposure to these environmental bacteria and the cow’s ability to resist an infection.
Exposure to environmental pathogen and infection pressure:
When considering the number of bacteria and infection pressure, it is important to look into the environmental management and housing hygiene of our dairy herds. During winter and for all year housed herds, the cubicle and housing environment are important areas to manage to reduce exposure to bacteria. In the summer months pasture management can affect the level of exposure cows have to some of these common mastitis causing bacteria. Cow cleanliness scoring allows visualisation and assessment of the hygiene of the herd and the cleanliness of the cow’s environment. Also assessing the milking cow’s environment is critical for the control of environmental mastitis and the implementation of changes to reduce the infection pressure. Examples of some environmental assessment areas include; straw yard management, cubicle management, ventilation, slurry management and pasture management.
Cow’s mastitis defence:
The other factor that will influence if a cow is affected by mastitis is her ability to resist an infection. There are a number of factors which have to be considered that can affect a cow’s natural defence mechanisms. Heat stress can reduce feed intake and result in a state of negative energy balance causing a reduction in immune defence. Concurrent diseases which cause a reduction in cow immune function can increase their susceptibility to mastitis e.g. Bovine Viral Diarrhoea virus (BVDv), (Wellenberga et al., 2002). Ensuring correct nutrition for all stages of a dairy cow’s lactation is critical in ensuring that they have an appropriate level of immunity to resist an infection. Dairy cattle should also be fed adequate levels of vitamin E and selenium (Hogan et al., 1993) as these are important in the cow’s immunity against mastitis causing pathogens.
The dry period is an important risk time in which environmental bacteria can have a detrimental impact on udder health. UK studies have demonstrated that greater than 50% of mastitis cases occurring in the first 100 days of lactation are caused by the common environmental pathogens as a result of infections acquired during the dry period (Bradley & Green, 2000). To help in control of the dry period risk it is important to manage the environmental pressure of the dry cow housing and also the defence of the udder during this time. It is important that the decisions regarding antibiotic dry cow therapy are made in consultation with your vet and a clean drying off technique is employed.
How can we assess factors which affect the incidence of environmental mastitis?
Vets are able to provide milk quality and mastitis investigations which enable recommendations to be made to reduce infection pressure and improve the cows own protective factors. The DairyCo Mastitis Plan is a format by which this investigation can be performed. It is a comprehensive questionnaire and on farm assessment of the cows’ environment to enable the identification of factors which can contribute to a mastitis problem. The plan enables a targeted control strategy to be made toward a herd individual mastitis profile, whether the cause is environmental or contagious pathogens.
Bradley, A.J. and Green, M.J. (2000) A study of the incidence and significance of intra-mammary enterobacterial infections acquired during the dry period. Journal of Dairy Science 83, 1957-1965.
Hogan, J.S., Weiss, W.P & Smith, K.L. (1993). Role of Vitamin E and Selenium in Host Defense Against Mastitis. Journal of Dairy Science. 76 (9), 2796-2803.
Wellenberga, G.J., van der Poelb, W.H.M, & Van Oirschot, J.T. (2002). Viral infections and bovine mastitis: a review. Veterinary Microbiology. 88 (1), 27-46.