Determination of risk factors for neonatal calf diarrhea using survival analysis

This study aimed to investigate the distribution of neonatal calf diarrhea according to various risk factors, estimate calf survival times and probabilities, and establish a multivariate model to identify significant risk factors. During the study period, 689 calves born on a farm were monitored throughout the neonatal period (1-28 days). Potential risk factors included calf-related variables (birth season, sex, breed, colostrum intake, colostrum intake method, twinning, birth weight, colostrum quality) and dam-related variables (dry period length, gestation length, calving type, age at first service, parity, number of artificial inseminations per conception). Cumulative survival probabilities and survival times were estimated using the Kaplan-Meier method. The Cox proportional hazards regression model was used to identify independent risk factors significantly associated with the hazard of neonatal diarrhea. Diarrhea was observed in 377 (54.7%) of the total 689 calves. The cumulative survival probability was 42.9% by day 28. The mean and median times to diarrhea onset were 17.9 and 14.0 days, respectively. The final multivariate model identified significant interactions: higher colostrum quality (HR: 0.848), higher birth weight in the absence of dystocia (HR: 0.991), and the time-dependent effect of birth weight (HR: 0.997) were associated with reduced hazard of diarrhea. In conclusion, this single-farm prospective study identifies colostrum quality and the interaction between birth weight and dystocia as significant predictors of time to neonatal diarrhea. The risk factors and their ratios provide managerial decision support for farmers. Furthermore, the results highlight the positive impact that strategies aimed at improving colostrum quality, achieving optimal birth weights, and reducing dystocia will have on calf health.