Yt. Grohn et al., ASSOCIATION BETWEEN PREVIOUS 305-DAY MILK-YIELD DISEASE IN NEW-YORK-STATE DAIRY-COWS, Journal of dairy science, 78(8), 1995, pp. 1693-1702
Logistic regression was used to examine the association between milk y
ield and disease. We studied 8070 cows of second or higher parity from
25 New York State Holstein herds, calving between June 1990 and Novem
ber 1993. Previous 305-d mature equivalent milk yield was used because
most of the disorders studied occurred too early in lactation for cur
rent milk yield to be considered. Seven disorders were studied: retain
ed placenta, metritis, ovarian cyst, milk fever, ketosis, abomasal dis
placement, and mastitis. A separate model was used for each disorder.
Each model included, in addition to milk yield, parity, calving season
, and herd. Results showed that higher milk yield was not a risk facto
r for any disease except mastitis. However, the association between hi
gher previous milk yield and mastitis does not necessarily imply causa
tion.