The effect of lameness treatments and treatments for other health disorders on the weight gain and feed conversion in boars at a Danish test station

Lameness in finishers can cause economic losses to farmers and lameness affects the welfare of pigs. In order to study the economic losses, we investigated the effect of lameness on productivity, measured as the mean daily weight gain (MDWG) and the feed conversion ratio (FCR), and evaluated the importance of these effects. The study design was observational of a cross sectional type and data was collected from a Danish boar test station during February 2002 and December 2004. A total of 10,473 boars were included in the study. We adapted a quantitative interpretation of lameness, using the number of lameness treatments of the individual animal, and generated the new variable: “lameness treatments”. All treatments other than lameness were recoded as “non-lameness treatments”. Multivariable hierarchical analyses were performed to assess the association between the risk factors: number of lameness treatments, records of non-lameness treatments (yes/no), breed (Duroc, Hampshire, Landrace, Yorkshire) and weight at 4 weeks with each of the outcome variables: MDWG and FCR. In order to improve the assumption of normality, we used a quadratic transformed MDWG and an inverse transformed FCR in the analyses. Lameness treatments had a significant effect on the transformed MDWG (p < 0.0001). Boars with one to three lameness treatments had a significant reduction in the MDWG, which corresponded to a reduction of 27 g per day. Boars with four and five lameness treatments did not have a significant reduction in the MDWG. More than five lameness treatments caused the largest reduction in the MDWG corresponding to 40 g per day. There was no significant association between lameness treatments and the transformed FCR (p = 0.14). Records of non-lameness treatments, breed and weight at 4 weeks were all significantly associated with the transformed MDWG and -FCR. Boars with records of non-lameness treatments had a reduction in the MDWG of 56 g per day and an increase in the FCR of 0.04 feed units per kg live weight. At the test station, the prevalence of boars with records of lameness treatments was 4% whereas the prevalence of records of non-lameness treatments was 65%.