Foot/leg and udder health in relation to housing changes in Swedish dairy herds.

Monthly herd disease incidence rate or prevalence estimates in 196 Swedish commercial dairy herds from 1988 to 1995 were collected retrospectively from the official milk-recording scheme and merged with county administrative and farmers' data on housing and management. To study the effects of changes in housing system on the occurrence of veterinary-treated foot/leg disorders, clinical mastitis, teat injuries and high milk somatic cell counts (MSCCs), four marginal Poisson or negative-binomial regression models were applied to the data (6011-7063 herd-month records), using the generalized estimating-equations method. Monthly observations were treated as repeated measures within herds. There were significant transitory increases in the incidence of clinical foot/leg disorders when changing from tie-stalls to cubicles and decreases in the incidences of clinical mastitis and teat injuries when changing from tie-stalls to cubicle or straw-yard systems. Effects on foot/leg health generally lasted for <18 months after building finish, while udder-health improvements persisted >18 months. Reductions in the incidence of clinical mastitis were not accompanied by any clear changes in the prevalence of high MSCCs.