It is worth remembering that a low rate of abortions are observed on all farms and three to five abortions per 100 pregnancies per year is considered normal.

Two of the most common causes of early abortion in cattle in Australia are the sexually transmitted diseases trichomoniasis and vibriosis.

A protozoon known as trichomonas foetus causes trichomoniasis. It is transmitted during breeding from infected bulls to susceptible cows.

Older bulls are more likely to be infected and remain infected than virgin or young bulls. Infections may result in abortion during the first five months of pregnancy.

Control of trichomoniasis within known infected herds is to begin artificial insemination, or to cull older bulls and only use young, clean bulls on heifers.

Even a switch in bull breeding to artificial insemination for six months will greatly reduce the effects of trichomoniasis.

Vibriosis is caused by a bacterium known as campylobacter fetus subsp venerealis.  

Infected bulls spread the disease during breeding. There are usually no clinical signs of disease in infected cows.

The primary sign is early abortion resulting in repeat breedings with a prolonged service interval. Occasional mid-term abortions are seen.

When vibriosis is first introduced into a herd, cows in all age groups are affected. Once established in a herd, vibriosis usually only affects the younger cows and heifers, as the older cows have developed immunity.

Control of vibriosis is through artificial insemination or vaccination. To be effective, vaccinations should be given prior to breeding each year.

Your veterinarian can make a diagnosis of both of these diseases by checking the sheath of suspected infected bulls.

For further information please contact your local veterinarian or Agriculture Victoria veterinary or animal health officer, or in New South Wales your Local Land Services.