title: Osteochondrosis, but not lameness, is more frequent among free-range pigs than confined herd-mates.
abstract: BACKGROUND
  Organic pig production is expanding and amongst the objectives of organic farming are enhancing animal health and welfare. However, some studies have reported a higher prevalence of lameness and joint condemnation at slaughter in free-range/organic pigs than in conventionally raised pigs. Organic slaughter pigs have free-range housing in which indoor and outdoor access is compulsory, while in conventional farming the pigs are commonly confined to indoor pens. The present study evaluated the effects of free-range and confined housing on lameness prevalence in a herd of 106 finisher pigs, and whether osteochondrosis and Erysipelothrix rhusiopathiae associated arthritis influences these effects. We also evaluated the association between clinical lameness during the rearing period and joint condemnations at slaughter.
  
  
  RESULTS
  Seventy free-range and 36 confined housed fattener pigs were scored for their gait twice during the rearing period and 848 joints were evaluated post mortem. Osteochondrosis was more frequent among free-range than confined pigs (P < 0.05), and when present it was also more severe (P < 0.001). Pigs with more numerous and more severe osteochondral lesions had their gait affected more than did pigs with fewer such lesions (P < 0.05). Hence it was a paradox that we did not detect more lameness among the free-range pigs than the confined pigs. E. rhusiopathiae associated arthritis was not diagnosed. The association between gait remarks/clinical lameness and joint condemnations at slaughter was not significant.
  
  
  CONCLUSIONS
  The results indicate that free-range housing may have both positive and negative effects on locomotory traits. Free-range pigs may be less clinically affected by osteochondrosis than are confined pigs. One explanation for this effect may be strengthening of joint supportive tissue and pain relief promoted by exercise. Visual gait scoring missed serious joint lesions that probably were harmful to the pigs, and should therefore not be used as a sole indicator of joint/leg health in welfare inspection of pigs. The association between gait scores and joint condemnation appeared to be poor. This study was limited to one herd, and so more and larger studies on the effects of free-range housing on lameness severity and osteochondrosis development in pigs are recommended.
authors.affiliation: Section of Pathology, Department of Biomedical Sciences and Veterinary Public Health, Swedish University of Agricultural Sciences (SLU), 750 07, Uppsala, Sweden. pernille.etterlin@slu.se.
authors.forename: Pernille Engelsen
authors.initials: PE
authors.lastname: Etterlin
authors.affiliation: Systematic Biology, EBC, Uppsala University, 752 36, Uppsala, Sweden. david.morrison@ebc.uu.se.
authors.forename: David A
authors.initials: DA
authors.lastname: Morrison
authors.affiliation: National Veterinary Institute (SVA), 751 89, Uppsala, Sweden. julia.osterberg@sva.se.
authors.forename: Julia
authors.initials: J
authors.lastname: Österberg
authors.affiliation: Terrestrial Ecology Department, Norwegian Institute for Nature Research (NINA), 7485, Trondheim, Norway. bjornar.ytrehus@nina.no.
authors.forename: Bjørnar
authors.initials: B
authors.lastname: Ytrehus
authors.affiliation: Swedish Animal Health Service (SvDHV), 464 32, Mellerud, Sweden. eva.heldmer@gardochdjurhalsan.se.
authors.forename: Eva
authors.initials: E
authors.lastname: Heldmer
authors.affiliation: Section of Pathology, Department of Biomedical Sciences and Veterinary Public Health, Swedish University of Agricultural Sciences (SLU), 750 07, Uppsala, Sweden. stina.ekman@slu.se.
authors.forename: Stina
authors.initials: S
authors.lastname: Ekman
mesh_terms: D000822:Animal Husbandry; D000818:Animals; D001168:Arthritis / Q000453:epidemiology* / Q000209:etiology; D004888:Erysipelothrix / Q000502:physiology; D005260:Female; D006799:Housing, Animal; D007794:Lameness, Animal / Q000453:epidemiology* / Q000209:etiology; D008297:Male; D058871:Organic Agriculture; D055034:Osteochondrosis / Q000453:epidemiology / Q000209:etiology / Q000662:veterinary*; D015995:Prevalence; D013548:Sweden / Q000453:epidemiology; D013552:Swine; D013553:Swine Diseases / Q000453:epidemiology* / Q000209:etiology; D013554:Swine Erysipelas / Q000453:epidemiology* / Q000382:microbiology