Locomotion scores in early gestation of younger parity sows are associated with fight lesions and body condition

Lameness in gilts and breeding sows is a major cause of premature removal or culling throughout the Australian pork industry, leading to economic and production losses (Dewey et al.1992; Anil et al. 2005). Although lameness can have many causes, the injuries acquired as a result of negative interactions and aggression between sows can be common in group-housing systems (Heinonen et al. 2013). The aim of this study was to investigate if lameness in gestating sows was associated with sow condition and the negative interactions between sows, such as fighting.

In total, 1,975 gestating gilts (P0) and parity one (P1) and two (P2) sows of Large White, Landrace and Duroc origins were recorded at a single site. The P0 sows were kept in pens of two, seven or 11, while older parity sows were moved to mixed parity groups of 11 in different sheds, after mating. All pens consisted of half concrete slats and half solid concrete flooring. Observations for all traits were taken at five weeks of gestation, by the same observer. Sow locomotive abilities were scored when sows were encouraged to stand and walk around their pen, ranging incrementally between 0 = normal movement (no evidence of lameness) and 3 = non-weight bearing on affected limb or an inability to walk. Sow condition was scored as average, over- or under-conditioned. Fight lesion scores were used to describe the extent and number of injuries present, ranging between 0 = no scratches present to 3 = > 10 scratches present, and lesions were classified as new or old. Sows were also noted as willing or unwilling to move, depending on whether encouragement to move was required: if encouragement was needed, the sow was classed as unwilling to move. Date of scoring, breed, and a term for parity/shed (gestation accommodation) were accounted for in the analyses as nuisance factors when required (P < 0.05), using linear models to identify associations between scores; treating one score as a dependant variable and the second as a class effect.

Over the complete study 87 sows exhibited some degree of lameness at five weeks of gestation, with locomotion scores of 1 or 2. No sows suffered from severe lameness (score 3). Concurrent scores for fight injuries, condition and willingness to move were all found to be significantly associated with locomotion score (P < 0.001). Sows with higher scores for fight lesions, over-conditioned or those unwilling to move had poorer locomotion scores (Table 1). However, age of the fight lesion (old vs new) was not associated (P > 0.05) with locomotion score. Date of recording was the only factor significant (P < 0.001) for locomotion score, as parity/shed and breed effects were not statistically significant. Over-conditioned sows were more likely (P < 0.001) to have fight lesions. Neither scores for condition or fight injuries were significantly associated with a sow’s willingness to move (P > 0.05). Date, parity/shed and breed significantly affected the incidence of fight injuries (P < 0.001), and to a lesser extent (and excluding date), sow condition (P < 0.05). None of these nuisance factors appeared to be associated with a sow’s willingness to move. The presence of fight injuries, over-conditioned sows and a lack of willingness to move were associated with the incidence of lameness in sows in early (five weeks) gestation. Developing strategies to reduce fighting and manage nutrition may have favourable outcomes for locomotion and condition of group-housed sows in early pregnancy.

Table 1.  The associations between fight lesions, condition, willingness to move and locomotion score