20 November 1998

More cases now due to environmental bacteria

By John Burns

A HIGHER proportion of mastitis cases are now caused by bacteria picked up from the environment than are passed from cow to cow during milking.

So said Devon vet Richard Sibley speaking at a Milk Development Council meeting at Seale Hayne, Newton Abbot. But clinical mastitis incidence has fallen to less than half what it was 30 years ago – thanks mainly to the five-point plan for mastitis control.

E coli is now a common cause of mastitis, and Strep uberis is another growing source. It is important to prevent these types of environmental mastitis because they are difficult to treat. S uberis tolerates antibiotics, so that cows appeared to recover, but could become chronic carriers, he said.

"Generally, prevention of environmental mastitis depends on avoiding infection getting into teats. The most hostile environment for bacteria is a dry one, so dry bedding, good ventilation, and drying teats after washing all helps mastitis control," he said.

Using medicated wipes or pre-milking teat dips can also help by killing bacteria on teats which can otherwise be pushed up through the teat canal by the milking machine action.

Teat ends closed

Making sure teat ends are closed before allowing cows to lie down is another approach. That can be helped by providing a dry atmosphere, as in damp air teat ends closed more slowly, and using a teat dip to seal teat ends after milking.

Maintenance of milking equipment was vital, he said. Mr Sibley believed infection was often introduced through the teat orifice during milking.

Choice of antibiotics for treating mastitis must be based on previous experience of what bacteria caused mastitis on that farm, he added. "Do not make your choice according to whether or not antibiotic tubes come with a free coat," he cautioned.

With average cow yield rising and, therefore, fewer cows needed to fill quota, the potential market for mastitis treatments is falling. Companies are fighting to keep market share by making many claims. "And if you do not believe them, then they offer you a free coat," said Mr Sibley.

Dry bedding and good ventilation are essential to avoid environmental mastitis bugs, such as E coli and Strep uberis, entering cows teats.