Mastitis and Cell Counts

Mastitis is a very costly disease resulting in increased milk wastage, treatment costs and culling rates.

A mastitis breakdown is normally a multi-factorial problem requiring an in depth investigation into the cause of the problem. The best approach to the problem is to take 10 to 20 individual milk samples from mastitic or high cell count cows and a bulk milk tank sample for laboratory culture and bacterial identification.

At Market Hall Vets, we offer a subsidised mastitis investigation service to help farmers identify the source(s) of the problem and then implement cost effective measures to eradicate the problem. If you are struggling with an increase in mastitis or cell counts then please contact the surgery for an informal discussion. If necessary, we will arrange to visit your farm and investigate the problem further.

Below are guidelines for interpreting mastitis milk sample results:

Strep agalactiae causes a contagious form of mastitis, that is spread from cow to cow at milking time. Infection is commonly sub clinical with clinical flare-ups. TBC from infected quarters may contain up to 100,000,000 bacteria per ml of milk and so Strep agalactiae can affect the bulk tank TBC level. Cell counts can also increase to very high levels with this form of mastitis.
Strep dysgalactiae is usually associated with teat damage, either chaps or physical damage that may be caused by poor milking machine function e.g. high vacuum levels, poor pulsation etc. Cell count increases moderately due to a build up of sub clinical infection. Infections tend to occur following sub clinical flare-ups.
Strep uberis is a mastitis organism that is present throughout the environment. It can produce mild to severe mastitis and can sometimes be difficult to treat. It can be shed in very high numbers by infected quarters, up to 100 million/ml of milk, and these have been known to increase the herd TBC level. Chronic cases of Strep uberis do occur.
Staph aureus is a contagious form of mastitis that spreads from cow to cow at milking time. These organisms will multiply on damaged and injured teats. Herd cell counts rise. This form of mastitis is frequently resistant to treatment as this organism buries itself in scar tissue in the udder where antibiotics cannot penetrate. This organism may be resistant to some of the common antibiotics, and so it is always advisable to use an intramammary product that is effective against all strains of Staph aureus. Culling is frequently the only solution to persistent Staph aureus cows.
Average success with treatment during lactation can vary from as low as 10% to at best 50%, and with dry cow therapy, no treatment is more than 65% successful. Staph aureus is always sensitive to the antibiotic Cloxacillin.
Coagulase negative (Coag -ve) Staphs commonly result in mastitis. They can be difficult to treat.
C bovisis found commonly in the teat canal where they grow up and infect the udder. C bovis are often associated with problems related to teat dipping, ie poor cover of teats, seasonal teat dipping.
E.coli is an environmental organism that is frequently the cause of acute mastitis after calving and may produce a mild to severe mastitis during lactation. There are over 200 strains of E. coli that can cause mastitis, and so sensitivity testing for this organism is of little value.
Yeasts occasionally cause mastitis. This form of mastitis will not respond to antibiotics. The quarters are frequently hard and swollen. Consult the surgery for treatment.
No Growth will occur in about 20% of all mastitis samples collected. This is due to a variety of possibilities that include the following; the mastitis organisms are no longer present, and have been eliminated from the udder, or the animal is, or has been recently, under treatment and this is interfering with growth.
Contaminated milk samples result when the end of the teat is not thoroughly disinfected before sample collection. Unfortunately, if any contaminants enter milk, they grow rapidly and swamp any mastitis organisms. The recommended collection procedure is described below;

Make sure your hands are clean and dry. Wash and dry the teat.
Scrub the teat-end thoroughly with either Mediwipes or cotton wool soaked in surgical spirit, until no further dirt is found on scrubbing.
Open a sterile sample bottle and hold it at a 45 degree angle.
Squirt a small amount of milk into the bottle, ensuring that you do not touch the teat-end.
Replace the cap and label the tube clearly.
Keep the sample in the fridge until you bring it into the practice.

Samples must be collected in sterile sample pots which are available from the practice. This should ensure that you get the best possible results from your milk samples.