Extreme care should be taken on farms where young calves are bought in for rearing, Teagasc experts have warned.
Replacement calves from other farms can be the main source of infection in a new outbreak of disease and the calves can be carriers of organisms to which homebred calves have acquired no resistance via their dam's colostrum.
"Where practicable, you should isolate purchased calves for a period to check for signs of disease," advises Teagasc's Bernadette Earley.
If possible, farmers should buy calves directly from the farm of origin, which minimises stress and reduces the risk of cross-infection between calves from different environments.
Every effort should be made to investigate the disease status of the farm prior to purchase. However, because some bought-in calves are sourced from the mart or agents, it is inevitable that there will have been mixing of animals before they reach the rearing farm.
There are some clear guidelines for farmers when sourcing young calves to bring back to the home farm. When purchasing, farmers should ensure that all calves are likely to have had an adequate intake of colostrums.
All calves should be inspected thoroughly -- healthy calves have a shining coat, a supple skin, a clean, damp nose and bright eyes.
Farmers should reject calves that are dull and listless, show signs of diarrhoea or have wet or thickened navels.
Buyers should also disregard calves that have discharges from the eyes, nose or mouth, show signs of heavy breathing or have physical defects.