Mastitis and the cow shed – John Davidson, Flett and Carmichael
Mastitis can be split into two groups; mastitis caused by contagious pathogens (bacteria that spread from cow to cow) and mastitis caused by environmental pathogens. With more dairy herds in Orkney turning to increased summer housing, combined with the long winters the challenge of keeping cows in a clean environment is a difficult but important one. Parlour management along with dry cow antibiotics has been very effective in reducing contagious mastitis but control of environmental mastitis has been much less effective so much so that it now accounts for more than 50% of mastitis cases in the UK dairy herd.
Environmental pathogens enter the udder by propulsion through the teat canal. This can happen at milking, inserting antibiotic tubes, inserting teat canulas or by penetration of the teat canal immediately after milking. The two most important bacterial causes of environmental mastitis are E.coli and Streptococcus uberis. Although most cases of environmental mastitis respond well to treatment with intramammary tubes many cases can become chronic or in the case of E.coli, become toxic. Both having large cost implications.
Control against pathogens found in the environment must focus on keeping the number of bacteria in the environment low by maintaining a clean and dry environment. E.coli comes from the cows gut so anywhere cow dung can come into contact with the udder is a potential source of infection. The dry period is just as important as the milking period for cows developing new mastitis infections and is not apparent until the cow develops clinical mastitis soon after calving. Having correctly sized cubicles for the type of cow and the type of bedding can make a difference. Generally sand is good because it contains less material for bacteria to grow in. For cattle kept on bedded courts keeping a dry top on the bed ‘squelch test’ and cleaning out every 4-6 weeks to prevent heating is essential. Overcrowding is a problem as this leads to more contamination within the environment and cows may lay in a passage instead of a dry cubicle. Calving boxes are also an important source ofinfection; these should be cleaned out after each use ensuring there is plenty of fresh bedding for every cow.
Dirty cows make getting teats clean a lot more challenging (NADIS).
Although the main spread of environmental bacteria is outside the parlour good milking management will reduce environmental mastitis. Ensuring teats are clean and dry before milking, foremilking and reducing impacts by careful cup removal will all help. During high risk periods a pre-dipping routine using an appropriate product could be added to the milking protocol. This will disinfect the teat and remove contamination and therefore reduce the number of bacteria in the bulk milk thus reducing bactoscan results. An important point to note about pre-dips is that the teats are cleaned before application, contact time is at least 30 seconds and the remaining dip is thoroughly wiped off the teat before the application of the cluster. Giving cows 30 minutes standing time after milking is also important as this gives the teat canal a chance to close and the post milking dip gets a chance to dry on without getting contaminated. When administering dry or lactating cow tubes it is important to do this in a sterile fashion taking short cuts can allow bacteria to be pushed up the canal and lead to further infections.
- Wear gloves
- Wash the teats and dry thoroughly
- Disinfect using a fast acting disinfectant or pre dip and wipe off after 30 seconds
- Wipe the teat with cotton wool soaked in surgical spirit
- Take the top off the tube, insert tip into teat and infuse
- Apply post milking disinfection dip
- Allow the teat canal to close by letting the cattle stand for 30 minutes in a clean yard
Antibiotic dry cow therapy and/or teat sealants reduce infections originating in the dry period, however the protection provided by dry cow antibiotics are not as good at the end of the dry period as in the beginning. The use of an internal teat sealant can help by providing a physical barrier until the cow is milked for the first time. As well as genetically selecting for good teat and udder confirmation regular servicing of the milking unit reduces liner slip and teat end damage, further enhancing the cows own defences.
Improving the cows’ immune response to mastitis is possible. Other disease problems can be a sign that the cow’s immune system may not be working as effective as it should be; making sure the diet is adequate in vitamins A, E, selenium and zinc all contribute to a healthy udder. There is also a vaccination available for some strains of mastitis, including E.coli, which will reduce the severity and number of clinical cases seen but will not eliminate a problem on its own.
Equipment needed to take a sterile milk sample
Somatic cell counts and bactoscan results are always going to vary with the time of year and individual farm circumstances but if an increased rate of clinical mastitis is being seen then it should be investigated. Taking a milk sample from a cow with clinical mastitis before treating them for the first time and freezing it allows for a selection of samples to be available for testing (bacteriology) should a mastitis problem arise (follow the same cleaning technique as the intramammary tube insertion to ensure an uncontaminated sample). It is now also possible to look for the DNA of bacteria even if treatment has already commenced. Since the methods of prevention and control of environmental pathogens versus contagious pathogens are different it is important to establish where the problem lies so that specific control programmes can be implemented.