High BMSCCs in mid-late lactation typically result from clinical or subclinical mastitis caused by cow-associated bacteria; most often the  Staph. Aureus  infection. This is more commonly seen in older cows and in those with chronic infections i.e. that have had a high somatic cell count at multiple herd tests. 
 
Staph. Aureus  is spread during the milking process via liners and hands. Hence, the most important control measures are to minimise cow to cow spread by ensuring that infected cows are identified and milked last and by ensuring that teat spraying continues and occurs at every milking using an effective teat spray applied properly. 
 
Staph. Aureus  is difficult to cure. Research studies in New Zealand and overseas find that the cure rate for staph cases is somewhere between 10% and 30% where “conventional” duration of therapy is used. Cure rates are lower in older cows, chronically infected animals and cows with multiple glands infected with  Staph. Aureus, where teat end damage is present, and where the isolate is resistant to penicillin. Studies here in New Zealand have found that about a third of the  Staph. Aureus  isolates are resistant to penicillin and require the use of different antibiotics. 
 
Increased bacteriological cure can be achieved by using longer duration of therapy with the appropriate antibiotic. However, the cost-benefit of doing so may become marginal due to milk discard costs. 
 
Our bulk milk culture promotion offered in December (10+ samples) will continue to run through until mid March so if you have recently had a herd test or have some problem cows you wish to check for infection (particularly to identify those cows with a  Staph. Aureus  infection), collect a pack from your local clinic. Milk cultures will help in deciding the best treatment option for these cows. 
 
If you are having problems or want to discuss your options please contact your vet or ask to speak to one of our vets with further mastitis training.