Incidence of Clinical Mastitis in a Herd of Holstein Cattle

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Abstract
Incidence of clinical mastitis in 760 lactations of 331 Holstein cows was studied for effects of sire, parity and month of calving. Incidence of clinical mastitis was higher in hind quarters than fore quarters. Positive correlations between number of cases in 1 quarter with number in other quarters and between proportion infected in 1 quarter and proportion infected in others indicated that occurrence of mastitis in 1 quarter was associated with above average frequencies of mastitis in the other quarters of the same cow. Clinical mastitis increased with increase in lactation number up to 4th lactation. Cows calving in Jan. and Feb. more frequently had mastitis than those calving in March and April.