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5 Oct 2020


Mastitis is defined as an infection in the udder tissue with bacteria or yeast fungus. Such infection can be clinical with local symptoms in the form of visible changes in the milk, redness, heat, swelling and/or tenderness of the infected udder gland. Other symptoms can be fever, loss of appetite, circulatory disorders or paralysis. Infection can also be sub clinical without any visible symptoms of illness but associated with a high cell count in the milk.

Investigations show that a temperature rise in a cow with mastitis can possibly interfere with reproduction processes, via heat stress. Heat stress in the period with oocyte maturation or early development of the embryo, reduces the survival chances of the embryo. Added to which, some of the bioactive molecules, that are formed with mastitis, indirectly interfere with reproduction and so inhibit embryo development and the chance of survival.


Classifying the problem

For the sake of the quality of the milk and animal welfare, there should no more than 20 percent of cows with > 200,000 cells/ml on performance checks and 25 cases of mastitis per 100 cow units.


Many different bacteria can cause chronic infections in the udders that will only sometimes be manifested in clinical mastitis. This primarily concerns infections with infectious bacteria Streptococcus agalactiae (B-streptococci) and Staphylococcus aureus. Infections of a more environment-related character, such as Streptococcus dysgalactia, Streptococcus uberis, enterococci and the group of coagulase negative staphylococci (CNS), can also be chronic.

On the other hand, acute clinical infections are often due to infections with micro bacteria, as those previously named, but to a large extent also infections with coliform bacteria such as E. coli and Klebsiella.

Points for action plan

To determine the causes of udder health problems, bacteriological tests are performed on single gland samples from cows with elevated cell counts when the primary problem is chronic infections and mastitis tests are done when the problem is clinical mastitis.

To prevent the spread of udder infections, the number of cows with chronic infectious disease should be limited, and they should be isolated from healthy cows, to avoid spreading infection during milking. Clinically ill animals are to be treated in accordance with the regulations and chronically infected animals ought to be dried off. In the case of infections with environmental bacteria, the focus should be on hygiene in the stalls and in walkways, bedding, general manure contamination and teat sealing of dried off cows.

Focus on

  • Bacteriological testing of single gland samples
  • Preventing any spread of infection to healthy cows
  • Hygiene in the stalls and walkways and adequate amounts of good quality bedding
  • Teat sealing of dry cows