The association of calfhood morbidity with first-lactation performance and milking herd survival in New York Holstein herds

The purpose of this study was to investigate the potential effects of diseases of dairy calves on performance in the milking herd. Data were collected prospectively from 26 dairy herds near Ithaca New York from 1983 to 1993. Herds were selected for the study that were milking between 35 and 200 Holstein cows, used Dairy Herd Improvement Records, usually bred cows by artificial insemination and had regularly scheduled herd health visits by New York State College of Veterinary Medicine Ambulatory Clinic veterinarians. Calfhood disease information was recorded from July 1983 through April 1985 on all heifer calves that survived at least 24 hours and were to be kept as herd replacements. Diseases were diagnosed by farmers until 90 days of age according to clinical descriptions provided by project personnel. The calfhood diseases studied were first occurrences of dullness (dull, listless, off-feed or droopy ears), respiratory disease (cough, runny nose or eyes, or trouble breathing), and scours or diarrhea. The associations of calfhood morbidity with age at first calving, first-lactation dystocia, retained placenta, breeding performance, and milk production, and length of milking herd life were examined. Multivariable statistical models were used to adjust for potential confounding variables and to account for herd effects. Of 1171 heifers entered into the study, 789 calved at least once before leaving the participating herds. Heifers with respiratory disease before 90 days had a decreased first-calving rate (hazard rate ratio = 0.5, 95% confidence interval (0.4, 0.8)) and higher risk of dystocia at first calving (odds ratio = 2.4, 95% confidence interval (1.0, 5.7)). These effects may reflect delayed growth among heifers affected by calfhood respiratory disease. Other potential associations identified were increased risk of retained placenta after the first calving for heifers with calfhood scours and increased days to first service and higher risk of being bred three or more times in first lactation for heifers diagnosed with dullness before 90 days of age. There were no significant associations of calfhood diseases with first-lactation calving interval, 305-day mature equivalent milk production, second test day milk production, or with survival in the milking herd.