Cryptosporidium muris: prevalence, persistency, and detrimental effect on milk production in a drylot dairy.

A total of 1746 individual fecal samples were obtained from milking cows during three separate visits to a drylot dairy farm. In addition, 1240 fecal samples were also obtained from cows in four additional farms. Cryptosporidium muris was prevalent in all five herds sampled. Cows that were sampled more than once invariably remained in the same shedding category. Cows shedding C. muris oocysts produced significantly less milk (approximately 3.2 kg/d). After corrections for the effects of age, parity, pen, and DIM in a logistic regression model, mean daily milk production was significantly associated with shedding status.