Risk factors for high herd level calf morbidity risk from birth to weaning in beef herds in the USA.

We analyzed data from a national survey of beef cow-calf producers in the USA to quantify the effects of hypothesized risk factors on herd-level calf morbidity risk from birth to weaning. The analysis included 2490 herds from 23 states. Two stepwise logistic regressions were fit to identify factors associated with &ge;10% morbidity. The first model included all herds dichotomized into high-morbidity herds with &ge;10% morbidity and low-morbidity herds with <10% morbidity. The second model excluded herds with between 5 and 10% morbidity, and compared >/=10% morbidity with </=5% morbidity. The risk of dystocia was categorized into five levels for analysis; all non-zero categories were associated with increased odds of being a high-morbidity herd compared to herds with no dystocia (OR=2.7-5.5). Having >70% of cows and heifers calves in confinement also increased the odds of being a high-morbidity herd (OR=1.8). The population attributable fractions for dystocia and confined calving for the model including all herds dichotomized at 10% morbidity were 0.41 and 0.11, respectively. The summary population attributable fraction for both factors was 0.46.