The effects of farming system and season on the prevalence of lameness in sheep in northwest Iran

Abstract

Aims: To determine the prevalence of lameness in sheep in Urmia, northwest Iran, and compare the effects of production system and season on prevalence.

Methods: A cross-sectional study, using cluster sampling, was conducted. The selected flocks included 18 with 2,315 sheep from farmed production and 28 with 7,619 sheep from semi-migratory systems, and were visited once in summer (grazing season) and once in winter (housing season). Sheep showing signs of lameness were examined to detect the causes of lameness. Bacteriology and histopathology were also performed if required.

Results: The probability of overall lameness was not affected by farming system (p = 0.40), but in the grazing season was less (OR = 0.62; 95% CI = 0.56-0.69) than in the housing season. Footrot was most the common cause of lameness, occurring in 1,047/1,880 (56%) cases. Among flocks, 40/46 (87%) had ≥ 1 case of footrot. Farming system had no effect on occurrence of footrot (p = 0.85), but the probability of footrot in the grazing season was less (OR = 0.21; 95% CI = 0.18-0.25) than in the housing season. Semi-migratory flocks had less hoof overgrowth (OR = 0.30; 95% CI = 0.16-0.56) than farmed flocks, and the probability of hoof overgrowth in the grazing season was less (OR = 0.19; 95% CI = 0.12-0.29) than in the housing season. The probability of digital abscess was less in semi-migratory flocks (OR = 0.64; 95% CI = 0.46-0.88) than farmed flocks, and in the grazing season was more (OR = 2.14; 95 CI = 1.61-2.85) than in the housing season. The probability of interdigital gland infection was higher (OR = 7.15; 95% CI = 5.36-9.55) in the grazing season than in the housing season. Staphylococcus aureus was isolated from 9/11 (82%) sheep affected with interdigital gland infection.

Conclusions: Footrot was the main cause of lameness in sheep in both farmed and semi-migratory farming systems in this study, especially in the housing season. In the grazing season, digital abscess and interdigital gland infection should be considered as common causes of sporadic lameness in sheep.

Clinical relevance: In practice, lameness in sheep can be a major concern both in farmed and semi-migratory farming systems, with a high occurrence in the housing season. Footrot was a main cause of lameness in sheep in northwest Iran.