Impact of prepartum hindlimb hoof lesions and other risk factors on the lameness status of sows at weaning: A prospective cohort study

Background Sow lameness represents a significant challenge to both animal welfare and economic efficiency in swine production, with hoof lesions identified as a major contributing factor. In China, research addressing sow lameness and its associated risk factors remains limited, particularly regarding longitudinal studies on risk factors for lameness in weaned sows. This study utilized a prospective cohort design to investigate the effects of pre-farrowing hindlimb hoof lesions and other factors including breed and parity on the development of lameness by weaning. Materials and methods A prospective cohort study was conducted from July to September 2024 on a multiplier sow farm (herd size = 5,159 sows) in Guangxi, China. The study cohort consisted of 311 non-lame sows, representing two genetic lines: Danish Yorkshire (YY) and Landrace (LL). At 110 days of gestation, one trained veterinarian performed standardized scoring for seven hindlimb conditions: overgrown toe (OT), overgrown dewclaw (ODC), heel overgrowth and erosion (HOE), heel-sole crack (HSC), white line crack (WLC), cracked wall horizontal (CWH) and cracked wall vertical (CWV). Lameness assessment were conducted during two key transition points: (1) pre-farrowing (transfer from gestation to farrowing rooms at 110 days of gestation) and (2) post-weaning (return to gestation rooms after weaning). Sows were monitored throughout lactation, with data collected on genetic line, parity, backfat thickness, and the requirement for farrowing assistance. Univariate analysis was conducted to identify candidate variables (hoof lesion types, genetic line, parity, backfat thickness, and farrowing assistance requirement). Then, these selected variables were incorporated into a multivariate logistic regression model to determine risk factors for lameness in sows at weaning. Variables with p -values < 0.1 were subsequently included in a multivariate logistic regression model to identify independent risk factors for lactation-associated lameness. Results Among sows that were non-lame at pre-farrowing assessment, 44.7% (139/311) developed lameness by weaning. Bilateral OT exhibited the highest adjusted odds ratio for incident lameness (OR = 42.5, 95% CI: 10.9-165.5; P  < 0.001), followed by unilateral OT (OR = 28.0, 95% CI: 9.4–83.7; P  < 0.001), bilateral HOE (OR = 10.0, 95% CI: 3.5–29.0; P  < 0.001), and bilateral ODC (OR = 7.3, 95% CI: 2.5–21.2, P  < 0.001). YY sows demonstrated a borderline significantly elevated risk compared to LL sows (OR = 2.3, 95% CI: 0.9–5.5; P  = 0.070). Conclusions Pre-farrowing hindlimbs lesions-including bilateral OT, ODC, HOE, and unilateral OT, were significant predictors of incident lameness at weaning. Biomechanical stresses during lactation may exacerbate pre-existing subclinical hoof lesions, leading to overt lameness at weaning. Prepartum hoof lesion scoring may thus serve as a valuable tool for risk stratification and early intervention strategies for improving sow welfare and farm productivity.