A case control study of on-farm risk factors for tail biting in pigs

Tail biting is an abnormal behaviour of pigs that is thought to have a multi-factorial origin. It is considered an unpredictable event on farms and is hard to reproduce experimentally. Therefore, a novel approach involving a case control study was used to investigate risk factors for tail biting on commercial units in England. Ninety-two pig farms across England were visited over a period of 11 months. At each visit, the owner or the manager of the unit was interviewed and the unit inspected. Data were recorded on standard forms. Farms were categorised into those that had tail biting in at least one pig in the past 6 months and those that had not. Univariate and logistic regression analyses yielded the following main results. Adding straw in the creep area once or more per day decreased the risk of tail biting 10-fold. Keeping grower pigs on partially or fully slatted floors versus solid floor increased risks of tail biting (odds ratio (OR) = 3.2). Using a feeding system with five or more grower pigs per feed space increased risks of tail biting (OR = 2.7). A stocking density during the growing phase of 110 kg/m(2) or greater increased risks of tail biting (OR = 2.7). Farms that belonged to a holding of five or more pig units had an increased risk of tail biting (OR = 3.5). As the number of pens per stockman increased by one, the risk of tail biting increased 1.06-fold. Tail biting was also associated with the following disease and production information: as the P2 back-fat value increased by I turn, the risk of tail biting decreased by 1.5-fold; post-weaning mortality above 2.5% was associated with a 3.9-fold increase in the risk of tail biting; presence of respiratory diseases was associated with a 1.6-fold increase in the risk of tail biting. Tail docking was associated with a three-fold increase in the risk of tail biting. This study has identified and quantified some management practices on commercial farms that can be changed to decrease the risk of tail biting in growing and finishing pigs.