Risk factors associated with tail damage in New Zealand dairy cattle.

Tail damage in dairy cattle is an increasingly recognised cause of poor welfare. However, there have been very few studies of the risk factors associated with the prevalence of tail damage. This analysis combined a 200-farm study of the prevalence of tail damage in New Zealand with a survey of farm management and handling practice with the aim of identifying the risk factors associated with tail damage (defined as either a deviated tail or one with evidence of other injury). Across the farms, the median herd level prevalence of tail damage was 11.5 %. The survey included 42 variables which were analysed at the univariable level. Factors which were identified as being potentially associated based on these univariable analyses included region, parlour type, milking frequency, use of automatic cup removers, use of coaxing to get cows to move and farmer's opinion of how many cows with tail damage they had. The final multivariable model had region, milking frequency (odds of tail damage 1.18 times higher for farms which always milked cows twice daily than for those which did not) and the use of coaxing (i.e. gentle persuasion) (odds of tail damage on farms which used coaxing was 0.83 times that on farms which did not). These results support the hypothesis that poor handling and/or interaction with infrastructure are important causes of tail damage on New Zealand dairy farms. More studies in more countries are needed to better understand the cause of tail damage in dairy cows. In addition, we need to standardise and optimise the repeatability of tail scoring.