Research trends in outdoor pig production - A review

  • Park, Hyun-Suk (Department of Animal Sciences, College of Agriculture and Environmental Sciences, North Carolina A&T State University) ;
  • Min, Byungrok (Department of Agriculture, Food and Resource Sciences, University of Maryland Eastern Shore) ;
  • Oh, Sang-Hyon (Department of Animal Sciences, College of Agriculture and Environmental Sciences, North Carolina A&T State University)
  • Received : 2017.04.29
  • Accepted : 2017.07.11
  • Published : 2017.09.01


Since the industrialization of swine production in the late 1900s, swine farms in the United States, as well as in Europe, have largely become consolidated. Pig farms became larger in size but fewer in number, with 91% of market pigs being produced by large operations with 5,000 or more pigs on-site in the US, and only 3% of the total utilized agricultural land representing organic farming. Such change in the market made it difficult for small farmers to stay competitive, forcing them to find alternative ways to reduce the cost of production and increase profit using the outdoor production system. In contrast to the indoor confinement system, outdoor production system uses pasture-based units and/or deep-bedded hoop structures that promote animal welfare and environmental sustainability with a lower capital investment. In accord with the growing concern for animal and environmental welfare and food safety by the consumers, small farmers practicing an outdoor production system are seeing increased opportunities for marketing their products in the pork niche market. Unlike the general belief that the reproductive and growth performance measures of the outdoor sows and piglets are poorer in comparison with the animals reared indoors, studies showed that there was no significant difference in the performance measures, and some traits were even better in outdoor animals. Improved reproductive and production traits can increase the sustainability of outdoor farming. Present study reviewed the recent studies comparing the performance measures, meat quality and health of indoor and outdoor animals, as well as the efforts to improve the outdoor production system through changes in management such as hut types and breed of animals.




  1. 2012 Census of Agriculture: United States summary and state data [Internet]. USDA; 2014 [cited 2017 Feb 10]. Available from:,_Chapter_1_US/usv1.pdf
  2. Pork stats. 2014. Pork checkoff. National Pork Board, Des Moines, IA, USA.
  3. Kapel CMO. Changes in the EU legislation on Trichinella inspection - New challenges in the epidemiology. Vet Parasitol 2005;132:189-94.
  4. von Borell E, Sorensen JT. Organic livestock production in Europe: aims, rules and trends with special emphasis on animal health and welfare. Livest Prod Sci 2004;90:3-9.
  5. Fruh B, Bochicchio D, Edwards S, et al. Description of organic pig production in Europe. Org Agric 2014;4:83-92.
  6. Hinrichs CC, Welsh R. The effects of the industrialization of US livestock agriculture on promoting sustainable production practices. Agric Hum Values 2002;20:125-41.
  7. Dawkins MS. Animal welfare and efficient farming: is conflict inevitable? Anim Prod Sci 2017;57:201-8.
  8. Miao ZH, Glatz PC, Ru YJ. Review of production, husbandry and sustainability of free-range pig production systems. Asian-Australas J Anim Sci 2004;17:1615-34.
  9. Honeyman MS. Extensive bedded indoor and outdoor pig production systems in USA: current trends and effects on animal care and product quality. Livest Prod Sci 2005;94:15-24.
  10. Johnson AK, Morrow-Tesch JL, McGlone JJ. Behavior and performance of lactating sows and piglets reared indoors or outdoors. J Anim Sci 2001;79:2571-9.
  11. Vaillancourt JP, Stein TE, Marsh WE, Leman AD, Dial GD. Validation of producer-recorded causes of preweaning mortality in swine. Prev Vet Med 1990;10:119-30.
  12. Johnson, AK, McGlone, JJ. Fender design and insulation of farrowing huts: effects on performance of outdoor sows and piglets. J Anim Sci 2003;81:955-64.
  13. Choi W, Nassif N, Whitley N, Oh SH. Comparison of temperature and humidity in three types of outdoor farrowing huts. Appl Eng Agric 2014;30:241-7.
  14. Akos K, Bilkei G. Comparison of the reproductive performance of sows kept outdoors in Croatia with that of sows kept indoors. Livest Prod Sci 2004;85:293-8.
  15. Lindgren Y, Lundeheim N, Boqvist S, Magnusson U. Reproductive performance in pigs reared under organic conditions compared with conventionally reared pigs. Acta Vet Scand 2013;55:33.
  16. Gentry JG, McGlone JJ, Miller MF, Blanton JR. Environmental effects on pig performance, meat quality, and muscle characteristics. J Anim Sci 2004;82:209-17.
  17. Patton BS, Huff-Lonergan E, Honeyman MS, et al. Effects of deep-bedded finishing system on market pig performance, composition and pork quality. Animal 2008;2:459-70.
  18. Honeyman MS, Harmon JD. Performance of finishing pigs in hoop structures and confinement during winter and summer. J Anim Sci 2003;81:1663-70.
  19. Dourmad JY, Hassouna M, Robin P, et al. Influence of pig rearing system on animal performance and manure composition. Animal 2009;3:606-16.
  20. Millet S, Raes K, Van den Broeck W, De Smet S, Janssens GPJ. Performance and meat quality of organically versus conventionally fed and housed pigs from weaning till slaughtering. Meat Sci 2005;69:335-41.
  21. Olsson V, Andersson K, Hansson I, Lundstrom K. Differences in meat quality between organically and conventionally produced pigs. Meat Sci 2003;64:287-97.
  22. Whitley N, Morrow W, See MT, Oh S-H. Comparison of growth performance of antibiotic-free yorkshire crossbreds sired by berkshire, large black, and tamworth breeds raised in hoop structures. Asian-Australas J Anim Sci 2012;25:1351-6.
  23. Gentry JG, McGlone JJ, Miller MF, Blanton JR. Diverse birth and rearing environment effects on pig growth and meat quality. J Anim Sci 2002;80:1707-15.
  24. Suzuki K, Shibata T, Kadowaki H, Abe H, Toyoshima T. Meat quality comparison of Berkshire, Duroc, and crossbred pigs sired by Berkshire and Duroc. Meat Sci 2003;64:35-42.
  25. Honeyman MS, Pirog RS, Huber GH, Lammers PJ, Hermann JR. The United States pork niche market phenomenon. J Anim Sci 2006;84:2269-75.
  26. Whitley N, Hanson D, Morrow W, See MT, Oh SH. Comparison of pork quality and sensory characteristics for antibiotic free Yorkshire crossbreds raised in hoop houses. Asian-Australas J Anim Sci 2012;25:1634-40.
  27. Brewer MS, Jensen J, Sosnicki AA, et al. The effect of pig genetics on palatability, color and physical characteristics of fresh pork loin chops. Meat Sci 2002;61:249-56.
  28. Dransfield E, Ngapo TM, Nielsen NA, et al. Consumer choice and suggested price for pork as influenced by its appearance, taste and information concerning country of origin and organic pig production. Meat Sci 2005;69:61-70.
  29. Maiorano G, Kapelanski W, Bocian M, Pizzuto R, Kapelanska J. Influence of rearing system, diet and gender on performance, carcass traits and meat quality of Polish Landrace pigs. Animal 2013;7:341-7.
  30. Millet S, Hesta M, Seynaeve M, et al. Performance, meat and carcass traits of fattening pigs with organic versus conventional housing and nutrition. Livest Prod Sci 2004;87:109-19.
  31. Bryhni EA, Byrne DV, Rodbotten M, et al. Consumer perceptions of pork in Denmark, Norway, and Sweden. Food Qual Pref 2002;13:257-66.
  32. Ngapo TM, Dransfield E, Martin J-F, et al. Consumer perceptions: pork and pig production. Insights from France, England, Sweden and Denmark. Meat Sci 2003;66:125-34.
  33. Stark KDC. Epidemiological investigation of the influence of environmental risk factors on respiratory diseases in swine - a literature review. Vet J 2000;159:37-56.
  34. Nansen P, Roepstorff A. Parasitic helminths of the pig: factors influencing transmission and infection levels. Int J Parasitol 1999;29:877-91.
  35. Jolie R, Backstrom L, Pinckney R, Olson L. Ascarid infection and respiratory health in feeder pigs raised on pasture or in confinement. Swine Health Prod 1998;6:115-20.
  36. Yonezawa T, Takahashi A, Imai S, et al. Effects of outdoor housing of piglets on behavior, stress reaction and meat characteristics. Asian-Australas J Anim Sci 2012;25:886-94.
  37. Guy JH, Rowlinson P, Chadwick JP, Ellis M. Health conditions of two genotypes of growing-finishing pig in three different housing systems: implications for welfare. Livest Prod Sci 2002;75:233-43.
  38. Tozawa A, Tanaka S, Sato S. The effects of components of grazing system on welfare of fattening pigs. Asian-Australas J Anim Sci 2016;29:428-35.
  39. Jensen TB, Toft N. Causes of and predisposing risk factors for leg disorders in growing-finishing pigs. CAB Rev Perspect Agric Vet Sci Nutr Nat Res 2009;4:No. 010.
  40. van Grevenhof EM, Ott S, Hazeleger W, et al. The effects of housing system and feeding level on the joint-specific prevalence of osteochondrosis in fattening pigs. Livest Sci 2011;135:53-61.
  41. Etterlin PE, Morrison DA, Osterberg J, et al. Osteochondrosis, but not lameness, is more frequent among free-range pigs than confined herd-mates. Acta Vet Scand 2015;57:63.
  42. Davies PR. Intensive swine production and pork safety. Foodborne Pathog Dis 2001;8:189-201.
  43. McComb L, Rump J. McDonald's USA Outlines 10-Year Plan for Ending Gestation Stall Use [Internet]. McDonald's Newsroom; 2012 [cited 2017 Feb 15]. Available from:

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