And the damage doesn't stop there. Mastitis is an infection of the udder caused by micro-organisms, usually bacteria. They normally enter the udder via the teat canal and multiply rapidly in the milk. The udder becomes inflamed, hard and very painful. Abscesses form and irreparable damage is done to the tissues such that often the udder eventually sloughs off.
Most cases occur in the first month of lactation when the udder is around peak milk yield.
Acute cases are clearly seen at this time. Chronic mastitis occurs when the infection subsides leaving abscesses that form hard lumps in the udder and teat canal. Often these are not noticed until udders are inspected at weaning. This presentation is probably better appreciated in dairying flocks but may also explain some of the variation in lamb performance to weaning in commercial flocks. We know quite a lot about the bacteria involved in cases of mastitis.