A longitudinal study into the effect of grazing on claw disorders in female calves and young dairy cows

To estimate the prevalence of claw disorders in youngstock and first parity heifers and to evaluate the effect of grazing on claw disorders, 10 Dutch dairy herds participated in a 2-year longitudinal study. Five herds were zero-grazed, while in the other five herds cows and youngstock had access to pasture during the summer. Twenty female calves <1 year of age and 20 females between 1 and 2 years of age were randomly selected on each farm, and were individually monitored at 3 monthly intervals for 2 years. Data from 366 animals with at least five observations were analysed using linear mixed models with a binomial error distribution. Independent variables were grazing, age, month of observation and previous occurrence of the disorder, while herd and animal were included as random effects. Of these 366 animals, 287 had calved once and 76 twice at the end of the study. Analytic results were obtained for digital dermatitis (DD), interdigital dermatitis/heel horn erosion (IDHE) and sole haemorrhages (SH), all of which had a prevalence of >15%. The prevalence of DD increased considerably around first calving on both the grazing and the zero-grazing farms. The prevalence of IDHE increased with age while SH prevalence showed a more fluctuating pattern. Digital dermatitis was less frequently observed in pastured animals than in permanently housed animals (OR=0.12-0.64 depending on month of observation; P<0.05), with the strongest effect being seen during the period when the herds which grazed cattle actually had animals at pasture (May to August). Grazing was also associated with lower levels of IDHE and SH, again particularly during the grazing season.