The application of event-time regression techniques to the study of dairy cow interval-to-conception

This paper explains the use of event-time techniques, also known as survival analysis, to assess a relationship involving dairy cows: the effect of early lactation milk yield on the interval from calving to subsequent conception. Possible confounding factors, such as disease history, parity, calving season, and herd production level, were controlled by their inclusion in the model equations.

Both Cox proportional hazards regression models and Weibull regression models were employed, with similar results, indicating that a Weibull distribution may be a good approximation of the distribution of conception times in dairy cattle.