24 May 2002

Reason unclear for summer cell count rise

TRADITIONAL summer increases in cell counts, coupled with a year-on-year rise could see many milk producers suffer price penalties in the coming months, but the reason for rises remains unclear.

NMR data shows that average counts in July and August are about 20% higher than from January to March says NMRs Mike Blanshard. "But average cell counts were 14% higher in the first quarter of 2002 than last year, at 197,000/ml, a repeat of the seasonal trend would see cell counts of 236,000/ml.

"This is close to the 250,000 marker used as an upper limit by many milk buyers." Cell counts above 250,000 could see a 100-cow herd producing 50,000 litres a month penalised by £250 a month.

But Glos vet Roger Blowey of the Wood Vet Group says the reasons why cell counts rise in summer are not fully understood. A possible reason, he suggests, is that cow yields decrease, particularly in autumn calving herds which begin drying off, concentrating cells in less milk.

"Another possibility is the tendency to use a cheaper teat dip, which may make a difference. But it is just as important to use a high quality dip in summer," he says.

The rise in cell counts year on year is also a concern and Mr Blowey believes an increase in incidence of Strep agalactiae could be a factor. "Over the past 12 months this bacterium has been found in more than 10% of bulk milk samples tested in our lab, although it was previously thought rare." Where this bug is found, discuss control options with a vet, he adds. &#42