Development and assessment of management practices in a flock-specific lameness control plan: A stepped-wedge trial on 44 English sheep flocks.

Lameness in sheep has economic and welfare implications, including loss of ewe body condition, lower lambing percentages, and poor lamb growth rates. It costs the UK sheep industry around £80 million per year. The majority of lameness is caused by the infectious diseases footrot and contagious ovine digital dermatitis, with white line separation, white line abscesses, and toe granulomas also reported by farmers. Most sheep farmers in the UK have other enterprises and care for their flock part-time. A lameness control plan (LCP) consisting of 37 management practices that covered all aspects of control of lameness was developed for part-time sheep farmers. Testing of the LCP was done using a stepped-wedge trial design with 7 visits to 44 flocks in England over 18 months. Flocks had 100-500 breeding ewes. Locomotion scoring was carried out at every visit, and farmers were interviewed every 6 months to record management practices. Clinical significance of changes in prevalence of lameness within each flock was analysed using the reliable change index (RCI). Management practices associated with prevalence of lameness were assessed using a multi-level multivariable over-dispersed Poisson model. The geometric mean (GM) prevalence of lameness at the start of the trial was 7.3% (95% confidence interval(CI) = 6.3-8.3%). Flocks with a clinically significant lameness reduction had a GM prevalence of lameness of 4.6% (95% CI = 4.1-5.2%), while flocks with a clinically significant increase in lameness had a GM prevalence of 10.5% (95% CI = 9.4-11.6%). Always separating lame sheep at treatment (relative risk (RR) = 0.60, 95% CI = 0.43-0.84) and culling sheep lame ≥2 occasions in a year (RR = 0.75, 95% CI = 0.61-0.92) were associated with a significant reduction in lameness. Compared with not footbathing at all, footbathing sheep when there were outbreaks of interdigital dermatitis reduced lameness (RR = 0.85, 95% CI = 0.75-0.96), however, 'routine' footbathing was not associated with a reduction in lameness. Housing during the previous lambing period was associated with a higher prevalence of lameness (RR = 1.23, 95% CI = 1.04-1.46). Vaccination in flocks with period prevalence ≥10% did not significantly reduce their risk of lameness compared to lower prevalence flocks. In conclusion, separating lame sheep at treatment, culling sheep lame ≥2 occasions per year, and only using a footbath to treat outbreaks of interdigital dermatitis are flock managements that contribute to improved control of lameness in flocks with part-time farmers.