The relationship between milk yield and the incidence of some diseases in dairy cows

Logistic regression models were used to examine the relationship between mi lk yield and incidence of certain disorders. Lactations (n = 2197) of 1074 Holstein-Friesian cows from 10 dairies (25 to 146 cows per dairy) in Lower Saxony were studied. The 305-d yield from the previous and current lactatio ns served as the standards for milk yield. Eight disorder complexes were co nsidered: retained placenta, metritis, ovarian cysts, mastitis, claw diseas es, milk fever, ketosis, and displaced abomasum. Each disorder complex was modeled separately. In addition to milk yield, the influences of the lactat ion number, the calving season and the other disorder complexes were examin ed with the "herd" factor taken into account. A correlation between retaine d placenta, mastitis, and milk fever to milk yield during the previous lact ation was found to be probable and for ketosis and displaced abomasum such a correlation was found to be possible. A connection to the yield in the cu rrent lactation was shown for ovarian cysts, claw diseases, and milk fever. No relationship to milk yield existed for metritis. An influence of the la ctation number was also demonstrated in various models. Single models allow ed a demonstration of the influences of both milk yield and lactation numbe r. Limitations of the model types are discussed.