22 October 1999

Environmental bugs hit low counts hard

LEAKING milk, straw yards, infrequent mucking out of calving areas and allowing cows access to an outdoor yard all contribute to an increased risk of clinical mastitis, according to a recent study.

Bristol vet schools Edmund Peeler told delegates that mastitis incidence has fallen from 120 cases/100 cows a year to 35-45 since 1960. But that had mainly been due to better control of contagious rather than environmental pathogens.

"There is evidence that low cell count herds suffer a higher level of environmental mastitis compared with higher cell count herds.

"Also, current mastitis control methods are less effective in controlling environmental pathogens compared with contagious pathogens," he said.

Dr Peeler reported results from a Milk Development Council-funded survey conducted on nearly 2000 units with cell counts less than 100,000/ml.

Data was analysed to determine management practices which might lead to an increased incidence of mastitis in herds.

"Cows leaking milk was the greatest mastitis risk factor. This may be because they have a wider teat canal which bacteria can penetrate more easily."

Other cows in the herd face exposure to bacteria in leaked milk, increasing their risk of catching the disease, he said.

Dirty yards

Housing in straw yards rather than cubicles, mucking out calving areas less frequently than once a month and dirty exercise yards are also significant mastitis risk factors, said Dr Peeler.

But offering fresh feed both after morning and evening milkings to keep cows standing could reduce mastitis risk, he advised. "Immediately after milking, the teat canal is more vulnerable to penetration by mastitis pathogens. This is more likely to occur when cows lie down rather than remaining standing after milking."