Are lower SCC cows more likely to get clinical mastitis than higher SCC cows in the same herd?
Dutch and American researchers studied whether low-SCC cows in one herd were more likely to show clinical mastitis. They wanted to find out how cows that had clinical mastitis differed from those that had increased SCCs but, at the same time, showed no clinical mastitis signs. The study herd milked 90 cows and had a bulk tank SCC test done about every two weeks. Over 12 years, only 10 of 288 tests were greater than 200,000 cells per millilitre. This showed a low incidence of subclinical mastitis (infection with no signs in the cow) during the study period. Yet clinical mastitis incidence was high. E. coli was the leading culprit, causing 43 per cent of the herd’ s clinical cases. When the researchers looked at factors common to clinically infected cows, they found characteristics identified in previous studies. For example, clinical mastitis was more likely to occur among cows in early lactation and among those with higher milk yield. As well, these cows were thinner, with body conditi
