Culling practices of Ontario cow-calf producers.

This study describes the distribution of herd culling rates for 123 Ontario cow-calf herds maintaining individual animal records. Associations between culling and factors at both the individual and herd level were examined. In addition, the relative importance of individual animal and herd level influences on culling were investigated. The following individual cow culling risk factors: nonpregnancy, age, weaning weight index, calf outcome, abortion, prolapsed vagina, prolapsed uterus, calving injury, lameness and mastitis or udder problems were significantly associated with culling (p less than 0.01). Two herd level factors were associated with increased culling rates: a higher than average proportion of heifers and a shorter than average calving season (p less than 0.01). The proportion of culling variation attributed to individual animal and herd level influences varied with model type. While simple models (one-way ANOVA) indicated that the herd variance component for culling was relatively minor, more complex models indicated larger herd-to-herd variability (mixed model ANOVA). Thus, it appeared that the probability of culling for a cow with a given set of risk factors depended to an important extent on manager decisions in the herd of origin.