Zero-inflated negative binomial regression model for dairyherds.

The (a) logistic and (b) negative binomial components of the zero-inflated negative binomial regression model predicting the likelihood of being a closed herd and the number of replacement breeding cattle purchased by dairy herds, respectively. (OR  =  odds ratio, CI  =  confidence interval, Coef  =  coefficient, SE  =  standard error)
Voung test V = 11.43, p<0.001
aThe culling rate was calculated as the percentage of calvings where the dam was subsequently slaughtered or sold within 500 days of calving.
bThe calf mortality rate was calculated as the percentage of all calves born during the specified time period that died on an agricultural holding within 365 days of birth.