Analysis of the relationship between workability traits and functional longevity in Canadian dairy breeds.

The aim of this study was to assess the effect of workability traits like milking speed and temperament on functional longevity of Canadian dairy cattle using a Weibull proportional hazards model. First-lactation data consisted of the following: 1,728,289 and 2,426,123 Holstein cows for milking temperament and milking speed, respectively, from 18,401 herds and sired by 8,248 sires; 39,618 and 60,121 Jersey cows for milking temperament and milking speed, respectively, from 1,845 herds and sired by 2,413 sires; and 54,391 and 94,847 Ayrshire cows for milking temperament and milking speed, respectively, from 1,316 herds and sired by 2,779 sires. Functional longevity was defined as the number of days from the first calving to culling, death, or censoring adjusted for production. Milking temperament and milking speed were recorded on a 1- to 5-point scale from very nervous to very calm and from very slow to very fast, respectively. The statistical model included the effects of stage of lactation; season of production; the annual change in herd size; type of milk recording supervision; age at first calving; effects of milk, fat, and protein yields calculated as within herd-year-parity deviations; herd-year-season of calving; sire; and milking temperament or milking speed class. The relative culling rate was calculated for animals in each milking temperament or milking speed class after accounting for the above-mentioned effects. The study showed that there was a statistically significant association between workability traits and functional longevity. Very nervous cows were 26, 23, and 46% more likely to be culled than very calm cows in Holstein, Ayrshire, and Jersey breeds, respectively. Similarly, very slow milkers were 36, 33, and 28% more likely to be culled than average milkers in Holstein, Ayrshire, and Jersey breeds, respectively. Additionally, very fast milkers were 11, 13, and 15% more likely to be culled than average milkers in Holstein, Ayrshire, and Jersey breeds, respectively. Producers might want to avoid consequences associated with the fast milkers such as udder health problems.