The udder becomes hard and hot with an abnormal discharge. In the recently calved cow the milk is thick, creamy and smells foul. The cow is often lame in one or both hind legs with swollen joints. Body temperature can be high and in some cases pregnant cows will abhort or produce a stunted calf. Around 4 out of ten cows are affected each year in Britain.
Sheep suffer similarly.
In really acute cases the ewe will have a raised temperature and the udder may start to turn a very dark colour as gangrene sets in. If this occurs, the whole or part of the udder can eventually slough off. In extreme cases, the ewe will rapidly die of septicaemia. Mild mastitis in sheep will result in permanent damage to the udder, usually in the form of abscesses, and ewes are often culled as a result. The remaining 520 were slaughtered in French abattoirs.