Interrelationships between production and reproductive diseases in Holstein cows. Conditional relationships between production and disease.

By methods of conditional odds ratio with a set of 2960 Holstein lactation records, relationships between occurrences of disease in a lactation were examined. There were strong positive relationships between retained placenta and metritis and between cystic follicle and luteal cyst. Interaction was among dystocia, retained placenta, and metritis and among retained placenta, cystic follicle, and luteal cyst. Metritis was an intervening variable between retained placenta and cystic follicle, retained placenta was a common cause variable for metritis and luteal cyst, and cystic follicle was either an intervening variable or a common cause for metritis and luteal cyst. Discriminant analyses were used to investigate production variables and other diseases as causes of disease, and multiple regression analyses indicated effects of disease on other diseases and current production in a subset of 810 lactation records. Breed class averages for milk and fat, days in milk, and dry period in one lactation had little effect on occurrence of disease in the subsequent lactation. Metritis, cystic follicle, and luteal cyst directly increased calving interval 20 to 27 days. Cystic follicle directly increased breed class averages 5.5 points. None of the five diseases directly increased days in milk.