Bovine viral disease
One of the most common diseases of cattle is bovine viral diarrhoea, caused by a Pestivirus. Although diarrhoea can be a transient occurance in previously unexposed cattle, it can cause abortions, congenital defects, the birth of weak calves and of calves that fail to thrive, as well as mucosal disease and diarrhoea in adult cattle.
Mucosal disease is a severe affliction that produces mouth ulcers, eruptive lesions on the hooves, and fever in 6–24-month-old animals, as well as diarrhoea and dysentery. Current research is looking at the feasibility of a disease control programme.
In cattle this disease is caused by the bacterium Mycobacterium avium spp. paratuberculosis, which is closely related to bovine tuberculosis. Johne’s disease affects the intestines, leading to diarrhoea, wasting or loss of body condition, and ultimately death. It is present at a low level in many dairy herds. Some infected animals show little or no signs of disease, but pass it on to others.
The disease is difficult to control because there is no accurate test. In 2008, vaccinations were done only where bovine TB was not present in wildlife, because of problems in developing a test that could distinguish between Johne's vaccination and TB. The only other method of control is to restrict contact between infected and uninfected animals.
This disease causes occasional dysentery and lost milk production in dairy cows. Salmonella Brandenburg can also cause abortions.
What is colostrum?
Colostrum is the first milk produced after giving birth. This special milk is yellow-orange, low in fat, and high in carbohydrates, protein, and antibodies. It is extremely easy to digest and provides perfect nutrition for a newborn, as well as living cells which provide defence against many harmful agents. The concentration of immune factors is much higher in colostrum than in mature milk.
Diarrhoea in calves
Calves are particularly susceptible to diarrhoea in their first month of life, especially if deprived of colostrum (the first milk produced by the mother). Colostrum is highly nutritious and contains antibodies to help fight infections.
Common infectious causes of diarrhoea in calves are rota virus, Salmonella, Escherichia coli infections and cryptosporidiosis. Some species of Coccidia can affect calves from about four weeks of age. Calves 6–12 months old can develop diarrhoea from yersiniosis (Yersinia pseudotuberculosis or Y. enterocolitica).