Mastitis: what is it and how is it prevented?

What is mastitis?

Mastitis is an inflammatory disease that affects the mammary tissues of a mammal, and is often associated with dairy cows. It is caused by  bacteria Staphylococcus Aureus, Streptococcus Uberis and E.Coli, amongst others, getting into the udder.   Mastitis is highly contagious. The infection can be spread by poor hygiene by milking staff who can carry the bacteria from an infected udder to another animal on their hands , or by incorrect separation and cleansing of milking equipment . Mastitis is not something to be encouraged in a dairy herd as infected milk has to be dumped  costing the dairy farmer money. Thus an infected animal will be placed on antibiotics quickly once symptoms become apparent.  These symptoms include the infected cow’s milk containing clots, being watery or bloody, her udder being hard, red and/or giving off heat, and the cow having less of an appetite, sunken eyes and a reduction in milk yield.


How is it prevented?

I volunteer on a dairy farm. On our farm mastitis is prevented primarily by maintaining good hygiene. Each cow has her udder cleansed prior to milking with a disinfectant foam and dried using a single use towelette. This also maintains good teat health as it prevents milking equipment being used on moist tissue which is then prone to damage and infection. In addition, care is taken to ensure that cows are always milked out fully so that milk is not left behind in the udder which would allow bacteria to feed on the lactose present in the milk residue in the udder. This means  we place some of our cows on a manual setting on the milking equipment which means we manually detach the milking unit from their udders at the appropriate time rather than  letting the unit shut off automatically when it detects the milk flow has stopped. This is done for those cows who do not have a strong milk let down and flow. This can mean the automatic milking unit  incorrectly computes a premature shut off point leaving milk behind in the udder elevating that animal’s risk of developing mastitis. In cases such as this we monitor the animal’s milk flow and when it drops to  a pre determined level and stays there we manually shut off the milking unit.

As mastitis is very contagious, any cows with mastitis are milked using a separate unit and their milk is dumped. These cows have their udders sprayed with a blue spray to highlight they are infected and that their milk is to be kept separate from milk taken from the healthy herd.  Infected milk must be disposed of as is not fit for human consumption due to the presence of infection, bacteria and antibiotics within it. Infected cows are segregated from the rest of the herd. All cows have their teats dipped after milking in  iodide foam and are bedded on clean hay beds. This helps prevent bacteria entering the udders after milking from environmental factors such as dirty bedding.

When necessary antibiotics are administered directly into the infected teat using a short plastic cannula. After squeezing the antibiotic up into the teat we pinch the end of the teat and palpate the antibiotic further up the teat.

If the mastitis is severe, it can result in the loss of a quarter of the udder. Although this shouldn’t affect the time taken for the cow to be milked out fully or the amount of milk she produces, her calf may not be kept or used for breeding as there are hereditary links with mastitis and so a cow that is prone to mastitis may have a calf that is also prone to mastitis.

An Introduction…

Hi, I am Niamh Duquemin, a 17-year old aspiring vet student, and I will be applying to study Veterinary Medicine this year. I am currently studying Chemistry, Biology, History and Maths at A-level and will be taking my AS exams in the summer. I plan on using this blog to document my work experience and comment on current veterinary news.


My non-academic interests include Netball, going to the gym and reading. I am also very passionate about History and enjoy researching around topics I’m learning, and have done horseriding since a young age.


I have wanted to study Veterinary Medicine form a very young age and have loved all of the work experience I’ve had the pleasure of partaking in so far and am greatly looking forward to the experience I have planned for the near future. I hope my blog can be of use and interest for other aspiring vets.