Asian-Australasian Journal of Animal Sciences

Asian Australasian Association of Animal Production Societies (아세아태평양축산학회)
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Review of Production, Husbandry and Sustainability of Free-range Pig Production Systems

  • Miao, Z.H. (Livestock Systems, South Australian Research and Development Institute, Roseworthy Campus) ;
  • Glatz, P.C. (Livestock Systems, South Australian Research and Development Institute, Roseworthy Campus) ;
  • Ru, Y.J. (Livestock Systems, South Australian Research and Development Institute, Roseworthy Campus)
  • Received : 2003.11.12
  • Accepted : 2004.06.09
  • Published : 2004.11.01
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Abstract

A review was undertaken to obtain information on the sustainability of pig free-range production systems including the management, performance and health of pigs in the system. Modern outdoor rearing systems requires simple portable and flexible housing with low cost fencing. Local pig breeds and outdoor-adapted breeds for certain environment are generally more suitable for free-range systems. Free-range farms should be located in a low rainfall area and paddocks should be relatively flat, with light topsoil overlying free-draining subsoil with the absence of sharp stones that can cause foot damage. Huts or shelters are crucial for protecting pigs from direct sun burn and heat stress, especially when shade from trees and other facilities is not available. Pigs commonly graze on strip pastures and are rotated between paddocks. The zones of thermal comfort for the sow and piglet differ markedly; between 12-22$^{\circ}C$ for the sow and 30-37$^{\circ}C$ for piglets. Offering wallows for free-range pigs meets their behavioural requirements, and also overcomes the effects of high ambient temperatures on feed intake. Pigs can increase their evaporative heat loss via an increase in the proportion of wet skin by using a wallow, or through water drips and spray. Mud from wallows can also coat the skin of pigs, preventing sunburn. Under grazing conditions, it is difficult to control the fibre intake of pigs although a high energy, low fibre diet can be used. In some countries outdoor sows are fitted with nose rings to prevent them from uprooting the grass. This reduces nutrient leaching of the land due to less rooting. In general, free-range pigs have a higher mortality compared to intensively housed pigs. Many factors can contribute to the death of the piglet including crushing, disease, heat stress and poor nutrition. With successful management, free-range pigs can have similar production to door pigs, although the growth rate of the litters is affected by season. Piglets grow quicker indoors during the cold season compared to outdoor systems. Pigs reared outdoors show calmer behaviour. Aggressive interactions during feeding are lower compared to indoor pigs while outdoor sows are more active than indoor sows. Outdoor pigs have a higher parasite burden, which increases the nutrient requirement for maintenance and reduces their feed utilization efficiency. Parasite infections in free-range pigs also risks the image of free-range pork as a clean and safe product. Diseases can be controlled to a certain degree by grazing management. Frequent rotation is required although most farmers are keeping their pigs for a longer period before rotating. The concept of using pasture species to minimise nematode infections in grazing pigs looks promising. Plants that can be grown locally and used as part of the normal feeding regime are most likely to be acceptable to farmers, particularly organic farmers. However, one of the key concerns from the public for free-range pig production system is the impact on the environment. In the past, the pigs were held in the same paddock at a high stocking rate, which resulted in damage to the vegetation, nutrient loading in the soil, nitrate leaching and gas emission. To avoid this, outdoor pigs should be integrated in the cropping pasture system, the stock should be mobile and stocking rate related to the amount of feed given to the animals.

Keywords

References

  1. Aarnik, A. J. A., D. Swierstra, A. J. van den Berg and L. Spellman. 1997. Effect of type of slatted floor and degree of fouling on solid floor on ammonia emission rates from fattening piggeries. J. Agric. Eng. Res. 66:93-102.
  2. Abbott, T. A., E. J. Hunter and H. J. Guise. 1996. Survey of management and welfare in outdoor pig production systems. Appl. Anim. Behav. Sci. 49:96-97.
  3. Andresen, N. and I. Redbo. 1999. Foraging behaviour of growing pigs on grassland in relation to stocking rate and feed crude protein level. Appl. Anim. Behav. Sci. 62:183-197.
  4. Andrews, F. N., W. E. Fontaine, A. A. Culver, T. L. Noffsinger and V. A. Garwood. 1960. Effectiveness of various types of shade on the growth of swine in a normal summer environment. J. Anim. Sci. 19:429-433.
  5. Anon. 1996. Farm Animal Welfare Council Report on the Welfare of Pigs Kept Outdoors. FAWC. Surrey, UK.
  6. Antequera, T., C. Lopez-Bote, J. J. Cordoba, C. Garcia, M. A. Asensio and J. Ventanas. 1992. Lipid oxidative changes in the processing of Iberian pig hams. Food Chem. 45:105-110.
  7. Azain, M. J., T. Tomkins, J. S. Sowinski, R. A. Arentson and D. E. Jewell. 1996. Effect of supplemental pig milk replacer on litter performance: seasonal variation in response. J. Anim. Sci. 74:2195-2202.
  8. Baker, B. 2002. Safeway: outdoor bred pork. http://www. racetothetop.org/case/case6.htm.
  9. Barb, C. R., M. J. Estienne, R. R. Kraeling, D. N. Marple, G. B. Rampacek, C. H. Rahe and J. L. Sartin. 1991. Endocrine changes in sows exposed to elevated ambient temperature during lactation. Domest. Anim. Endo. 8:117-127.
  10. Barnett, J. L., P. H. Hemsworth, G. M. Cronin, E. C. Jongman and G. D. Hutson. 2001. A review of the welfare issues for sows 2001 and piglets in relation to housing. Aust. J. Agric. Res. 52:1-28.
  11. Barton-Gade, P. 2002. Welfare of animal production in intensive and organic systems with special reference to Danish organic pig production. Meat Sci. 62:353-358.
  12. Barton-Gade, P. and L. O. Blaabjerg. 1989. Preliminary observations on the behaviour and meat quality of free range pigs. Proc. 35th Int. Cong. Meat Sci. Technol. pp. 1002-1005.
  13. Berger, F., J. Dagorn, M. Le. Denmat, J. P. Quillien, J. C. Vaudelet and J. P. Signoret. 1998. Perinatal losses in outdoor pig breeding. A survey of factors influencing piglet mortality. Ann. Zootechnol. 46:321-329.
  14. Black, J. L., R. G. Campbell, I. H. Williams, K. J. James and G. T. Davies. 1986. Simulation of energy and amino acid utilisation in the pig. Res. Devel. Agric. 3:121-145.
  15. Black, J. L., B. P. Mullan, M. L. Lorschy and L. R. Giles. 1993. Lactation in the sow during heat stress. Livest. Prod. Sci. 35:153-170.
  16. Blackshaw, J. K. and A. W. Blackshaw. 1994. Shade-seeking and lying behaviour in pigs of mixed sex and age, with access to outside pens. Appl. Anim. Behav. Sci. 39:249-257.
  17. Blasetti, A., L. Boitani, M. C. Riviello and E. Visalberghi. 1988. Activity budgets and use of enclosed space by wild boars (sus scrofa) in captivity. Zoo Biol. 7: 69-79. https://doi.org/10.1002/zoo.1430070108
  18. Bransby, D. I. 1993. Effects of grazing management practices on parasite load and weight gain of beef cattle. Vet. Parasitol. 46:215-221. https://doi.org/10.1016/0304-4017(93)90060-Z
  19. Bray, C. I. and C. B. Singletary. 1948. Effect of hog wallows on gains of fattening swine. J. Anim. Sci. 7:521.
  20. Buckner, L. J., S. A. Edwards and J. M. Bruce. 1998. Behaviour and shelter use by outdoor sows. Appl. Anim. Behav. Sci. 57:69-80.
  21. Capstick, J. W. and T. B. Wood. 1922. The effect of change in temperature on the basal metabolism of swine. J. Agri. Sci. 12:257.
  22. Cargill, C. 2002. Optimising water intake to maximise health and production in sows. 1st ASEAN Pork Challenge. Pasig City, The Philippines. p. 42.
  23. Carran, R. A., P. W. Theobald and J. P. Evans. 1995. Emission of nitrous oxide from some grazed pasture soils in New Zealand. Aust. J. Soil Res. 33:341-352.
  24. Ciordia, H., W. E. Neville, D. M. Baird and H. C. McCampbell. 1971. Internal parasitism of beef cattle on winter pastures: levels of parasitism as affected by stocking rates. Am. J. Vet. Res. 32:1353-1358.
  25. Clark, J. R., A. Komkov and L. F. Tribble. 1986. Effects of parity, season, gonadotrophin releasing hormone and altered suckling intensity on the interval to rebreeding in sows. Theriogenology 26:299-308.
  26. Costa, O. A. D., A. F. Girotto, A. S. Ferreira and G. J. M. N. de Lima. 1995. Economic analysis of intensive confinement and outdoor swine production systems during gestation and lactation. Revista da Sociedade Brasileira de Zootecnia 24:615-622.
  27. Csermely, D. 1994. Maternal behaviour of free ranging sows during the first 8 days after farrowing. J. Ethol. 12:53-62.
  28. Culver, A. A., F. N. Andrews, J. H. Conrad and T. L. Noffsinger. 1960. Effectiveness of water sprays and a wallow on the cooling and growth of swine in a normal summer environment. J. Anim. Sci. 19:421-428.
  29. Dagorn, J., B. Badouard and S. Boulot. 1996. Free range pig farming in France. Techni. Porc. 19:7-13.
  30. Dailey, J. W. and J. J. McGlone. 1997a. Oral/nasal/facial and other behaviors of sows kept individually outdoors on pasture, soil or indoors in gestation crates. App. Anim. Behaviour Sci. 52:25-43.
  31. Dailey, J. W. and J. J. McGlone. 1997b. Pregnant gilt behaviour in outdoor and indoor intensive pork production systems. App. Anim. Behaviour Sci. 52:45-52.
  32. Dano, R. and H. B. Bogh. 1999. Usage of herbal medicine against Helminths in livestock. An old tradition gets its renaissance. Wld. Anim. Rev. 93 (2):60-65.
  33. Dardaillon, M. 1989. Age-class influences on feeding choices of free-ranging wild boars (sus scrofa). Can. J. Zool. 67:2792-2796.
  34. De Jonge, F. H., E. A. M. Bokkers, W. G. P. Schouten and F. A. Helmond. 1996. Rearing piglets in a poor environment: Developmental aspects of social stress in pigs. Physiol. Behav. 60:389-396.
  35. Delbor, C., F. Beaudeau and F. Berger. 2000. Production implications of teeth clipping and iron injection of piglets born in outdoor systems. 32emes Journees de la Recherche Porcine en France, Paris, France. 1, 2, et 3 fevrier 2000. 32:129-134.
  36. Downey, N. E. and A. Conway. 1968. Grazing management in relation to trichostrongylid infestation in lambs. Ir. J. Agric. Res. 7:343-362.
  37. Dworschak, E., E. Barna, A. Gergely, P. Czuczy, J. Hovari, M. Kontraszti, O. Gaal, L. Radnoti and G. Biro. 1995. Comparison of some components of pigs kept in natural (free-range) and large-scale conditions. Meat Sci. 39:79-86.
  38. Edwards, S. A., K. A. Atkinson and A. B. Lawrence. 1993. The effect of food level and type on behaviour of outdoor sows. In: Proceedings of the 27th International Congress of the International Society for Applied Ethology, Berlin, 1993, pp. 501-503.
  39. English, P. R. and W. J. Smith. 1975. Some causes of death in neonatal piglets. Vet. Ann., 15:95-104.
  40. Eriksen, J. 2001. Implications of grazing by sows for nitrate leaching from grassland and the succeeding cereal crop. Grass and Forage Sci. 56:317-322.
  41. Eriksen, J. and K. Kristensen. 2001. Nutrient excretion by outdoor pigs: a case study of distribution, utilization and potential for environmental impact. Soil Use and Manage. 17:21-29.
  42. Fritschen, R. D. 1975. Toilet training of pigs on partly slatted floors. University of Nebraska, Lincoln, NebGuide G 74-40.
  43. Garrett, W. N., T. E. Bond and C. F. Kelly. 1960. Environmental comparisons of swine performance as affected by shaded and unshaded wallows. J. Anim. Sci. 19:921-925.
  44. Geers, R., V. Goedseels, G. Parduyns and G. Vercruysse. 1986. The group postural behaviour of growing pigs in relation to air velocity, air and floor temperature. Appl. Anim. Behav. Sci. 16:353-362.
  45. Gentry, J. G., J. J. McGlone, M. F. Miller and J. R. Blanton, Jr. 2002a. Diverse birth and rearing environment effects on pig growth and meat quality. J. Anim. Sci. 80:1707-1715.
  46. Gentry, J. G., J. J. McGlone, J. R. Blanton, Jr. and M. F. Miller. 2002b. Alternative housing systems for pigs: influences on growth, composition, and pork quality. J. Anim. Sci. 80:1781-1790.
  47. Gentry, J. G., J. J. McGlone, J. R. Blanton, Jr. and M. F. Miller. 2002c. Impact of spontaneous exercise on performance, meat quality, and muscle fibre characteristics of growing/finishing pigs. J. Anim. Sci. 80:2833-2839.
  48. Giles, L. R. and J. L. Black. 1991. Voluntary food intake in growing pigs at ambient temperatures above thermal neutral. In Manipulating Pig Production III (Ed. E. S. Batterham). Australasian Pig Science Association, Werribee, pp. 162-165.
  49. Grandin, T. 1989. Environment and genetic effects on hog handling. ASAE Annual Meeting, New Orleans, LA. Paper no. 894514.
  50. Graves, H. B. 1984. Behaviour and ecology of wild and feral swine (Sus scrofa). J. Anim. Sci. 58:482-492. https://doi.org/10.2527/jas1984.582482x
  51. Guy, J. H., P. Rowlinson, J. P. Chadwick and M. Ellis. 2002. Behaviour of two genotypes of growing-finishing pig in three different housing systems. Appl. Anim. Behav. Sci. 75:193-206.
  52. Hacker, R. R., J. R. Ogilvie, W. D. Morrison and F. Kains. 1994. Factors affecting excretory behaviour of pigs. J. Anim. Sci. 72:1455-1460.
  53. Hansen, J. W., P. Nansen and J. Foldager. 1981. The importance of stocking rate on the uptake of gastrointestinal nematodes by grazing calves. In: The Epidemiology and Control of Nematodiasis in Cattle. (Ed. P. Nansen, R. J. Jorgensen and E. J. L. Soulsby). Proc. of the CEC Workshop, Copenhagen. Martinus Nijhoff, The Hague, pp. 471-494.
  54. Heitman, H., L. Hahn, T. E. Bond and C. F. Kelly. 1962. The effects of modified summer environment of swine behaviour. Anim. Behav. 10:15-19.
  55. Heitman, H. Jr and E. H. Hughes. 1949. The effects of air temperature and relative humidity on the physiological wellbeing of swine. J. Anim. Sci. 8:171.
  56. Henschke, I. 1999. Free-range pigs. http://www.abc.net.au/landline/1101039.html.
  57. Hogberg, A., J. Pickova, P. C. Dutta, J. Babol and A. C. Bylund. 2001. Effect of rearing system on muscle lipids of gilts and castrated male pigs. Meat Sci. 58:223-229.
  58. Horrell, I. And P. A’Ness. 1996. The nature, purpose and development of rooting in pigs. In: Proceedings of the 30th International Congress of the International Society for Applied Ethology, Guelph, Ont., Canada, 14-17 August 1996, p. 100.
  59. Ingram, D. L. 1965. Evaporative cooling in the pig. Nature 207:415-416. https://doi.org/10.1038/207415a0
  60. Jackson, A. D. 1938. Fattening hogs need conrete wallow in hot weather. Progress report. Texas Agr. Exp. Stat., Texas A and M College.
  61. Jensen, P. 1986. Observations on the maternal behaviour of freeranging domestic pigs. Appl. Anim. Behav.Sci. 16:131-142.
  62. Jensen, P. 1994. Fighting between unacquainted pigs-effects of free-ranging domestic pigs. Appl. Anim.Behav.Sci. 41:37-52.
  63. Jensen, M. B., I. Kyriazakis and A. B. Lawrence. 1993. The activity and straw directed behaviour of pigs offered foods with different crude protein content. Appl. Anim. Behav. Sci. 37:211–221.
  64. Jensen, P. and D. G. M. Wood-Gush. 1984. Social interactions in a group of free-ranging sows. Appl. Anim. Behav. Sci. 12:327-337.
  65. Johnson, A. K., J. L. Morrow-Tesch and J. J. McGlone. 2001. Behaviour and performance of lactating sows and piglets reared indoors or outdoors. J. Anim. Sci. 79:2571-2579.
  66. Jones, J. E. T. 1966. Observations on parturition in the sows: Part II: The parturient and postparturient phases. Br. Vet. J. 122:471-478.
  67. Karg, H. and G. Bilkei. 2002. Causes of sow mortality in Hungarian indoor and outdoor pig production units. Berliner und Munchener Tierarztliche Wochenschrift 115:366-368.
  68. Kongsted, A. G. and V. A. Larsen. 1999. Piglet mortality in outdoor sow herds. DJF Rapport, Husdyrbrug. No. 11, p. 56.
  69. Kraglund, H. O. 1999. Survival, development and dispersal of the free-living stages of Ascaris suum, Oesophagostomum dentatum and Trichuris suis at the pasture. Ph.D. Thesis. The Royal Veterinary and Agricultural University, Copenhagen, Denmark, pp. 1-124.
  70. Kyriazakis, I. and G. C. Emmans. 1991. Diet selection in pigs: dietary choices made by growing pigs following a period of underfeeding with protein. Anim. Prod. 52:337-346.
  71. Larsen, M. N. 1996. ${\AA}$rstidsvariation i overlevelse, udvikling og spredning for 4 porcine parasitter p${\aa}$ friland, M.Sc. Thesis, University of Copenhagen.
  72. Larsen, V. Aa. and E. Jorgensen. 2002. Reproductive performance of outdoor sow herds. Livest. Prod. Sci. 78:233-243.
  73. Larsen, M. N. and A. Roepstorff. 1999. Seasonal variation in development and survival of Ascaris suum and Trichuris suis eggs on pasture. Parasitology 119:209-220.
  74. Leite, D. M. G., N. W. Pereira, A. O. D. Costa, G. A. Vargas and A. Silva. 2000. Parasitoses in outdoor pig production. A. Hora Veterinaria 19:8-10.
  75. Leite, D. M. G., A. Silva and G. A. Vargas. 2001. Causes of mortality of piglets in outdoor pig production. A Hora Veterinaria 21:9-12.
  76. Lopez Bote, C. J. 1998. Sustained utilization of the Iberian pig breed. Meat Sci. 49:s17-s27.
  77. Lopez Bote, C. J. and A. I. Rey. 2001. Susceptibility of hepatic tissue of Iberian pigs is enhanced by free-range feeding and reduced by vitamin E supplementation. Nutr. Res. 21:541-549.
  78. Maxwell, R. C., R. S. Cutler and A. P. L. Callinan. 1990. Drip cooling lactating sows improves performance and comfort. In: Proc. 11th IPVS. p. 396.
  79. Mayoral, A. I., M. Dorado, M. T. Guillen, A. Robina, J. M. Vivo, C. Vazquez and J. Ruiz. 1999. Development of meat and carcass quality characteristics in Iberian pigs reared outdoors. Meat Sci. 52:315-324.
  80. McCormik, W. C., O. M. Hale and B. L. Southwell. 1956. The value of a water sprinkler for fattening pigs during summer. Ga. Agr. Exp. Stat. Mimeo. Series N.S. 27.
  81. McGlone, J. J. 1987. An examination of behavioural, immunological and productive traints in four management systems for sows and piglets. Appl. Anim. Behav. Sci. 18:269-286. https://doi.org/10.1016/0168-1591(87)90222-X
  82. McGlone, J. J. and T. A. Hicks. 2000. Farrowing hut design and sow genotype (Camborough-15 vs. 25% Meishan) effects on outdoor sow and litter productivity. J. Anim. Sci. 78:2832-2835.
  83. McGlone, J. J., W. F. Stansbury and L. F. Tribble.. 1988. Management of lactating sows during heat stress: effects of water drip, snout coolers, floor type and a high energy-density diet. J. Anim. Sci. 66:885-891.
  84. Mejer, H., L. E. Thomsen and S. Wendt. 1998. Transmission af helminther hos grise p${\aa}$ friland. Betydning af n${\ae}$sering, bel${\ae}$gningsgrad, fodersammens${\ae}$tning og adf${\ae}$rd, M.Sc.Thesis, University of Copenhagen.
  85. Mejer, H., S. Wendt, L. E. Thomsen, A. Roepstorff and O. Hindsbo. 2000. Nose-rings and transmission of helminthes in outdoor pigs. Acta Vet. Scand. 41:153-165.
  86. Metcalfe, E. 2001. The pig issue. http://www.theecologist.org/ archive_article.html?article=240&category=64.
  87. Mullan, B. P., W. Brown and M. Kerr. 1992. The response of the lactating sows to ambient temperature. Proc. Nutr. Soc. Aust. 17:215 (abstract).
  88. Mullan, B. P., W. H. Close and G. R. Foxcroft. 1991. Metabolic state of the lactating sow influence plasma LH and FSH before and after weaning. In: Manipulating Pig Production III. (Ed. E. S. Batterham). Aust. Pig Sci. Assoc, Werribee. p. 31 (abstract).
  89. Muriel, E., J. Ruiz, J. Ventanas and T. Antequera. 2002. Free-range rearing increases (n-3) polyunsaturated fatty acids of neutral and polar lipids in swine muscles. Food Chem. 78:219-225.
  90. Nansen, P., J. Foldager, J. W. Hansen, Sv. Aa. Henriksen and R. J. Jorgensen. 1988. Grazing pressure and acquisition of Ostertagia ostertagi in calves. Vet. Parasitol. 27:325-335.
  91. Nansen, P., M. Larsen, A. Roepstorff, J. Gronvold, J. Wolstrup and S. A. Henriksen. 1996. Control of Oesophagostomum dentatum and Hyostrongylus rubidus in outdoor-reared pigs through daily feeding with the microfungus Duddingtonia flagrans. Parasitol. Res. 82:580-584.
  92. Nansen, P. and A. Roepstorff. 1999. Parasitic helminths of the pig: factors influencing transmission and infection levels. Intern. J. Parasitol. 29:877-891.
  93. Olsen, A. W. 2001. Behaviour of growing pigs kept in pens with outdoor runs. 1. Effect of access to roughage and shelter on oral activities. Livest. Prod. Sci. 69:255-264. https://doi.org/10.1016/S0301-6226(01)00172-5
  94. Olsen, A. W., L. Dybkjær and H. B. Simonsen. 2001. Behaviour of growing pigs kept in pens with outdoor runs. II. Temperature regulatory behaviour, comfort behaviour and dunging preferences. Livest. Prod. Sci. 69:265-278.
  95. Perera, A. N. M. and R. R. Hacker. 1984. The effects of different photoperiods on reproduction in the sow. J. Anim. Sci. 58:1418-1422.
  96. Petersen, S. O., K. Kristensen and J. Erikesen. 2001. Denitrification losses from outdoor piglet production: spatial and temporal variability. J. Environ. Quality 30:1051-1058.
  97. Petersen, V., B. Recen and K. Vestergaard. 1990. Behaviour of sows and piglets during farrowing under free-range conditions. Appl. Anim. Behav. Sci. 26:169-179.
  98. Petersen, V., H. B. Simonsen and L. G. Lawson. 1995. The effect of environmental stimulation on the development of behaviour in pigs. Appl. Anim. Behav. Sci. 45:215-224.
  99. Petkevicius, S., K. E. Bach Knudsen, P. Nansen and A. Roepstorff. 1996. The influence of diet on infections with Ascaris suum and Oesophagostomum dentatum in pigs on pasture. Helminthologia 33:173-180.
  100. Petkevicius, S., M. Larsen, K. E. Back Knudsen, P. Nansen, J. Gronvold and H. Bjorn. 1998. The effect of the nematodedestroying fungus Duddingtonia flagrans against Oesophagostomum dentatum larvae in faeces from pigs fed different diets. Helminthologia 35:111-116.
  101. Petkevicius, S., P. Nansen, K. E. B. Knudsen and F. Skjoth. 1999. The effect of increasing levels of insoluble dietary fibre on the establishment and persistence of Oesophagostomum dentatum in pigs. Parasite. 6:17-26.
  102. Prunier, A., J. Y. Dourmad and M. Etienne. 1994. Effect of light regimen under various ambient temperatures on sow and litter performance. J. Anim. Sci. 72:1461-1466.
  103. Quiniou, N., D. Renaudeau, S. Dubois and J. Noblet. 2000. Effect of diurnal fluctuating high ambient temperatures on performance and feeding behaviour of multiparous lactating sows. Anim. Sci. 71:571-575.
  104. Rachuonyo, H. A., W. G. Pond and J. J. McGlone. 2002. Effects of stocking rate and crude protein intake during gestation on ground cover, soil-nitrate concentration, and sow and litter performance in an outdoor swine production system. J. Anim. Sci. 80:1451-1461.
  105. Randall, J. M., A. W. Armsby and J. R. Sharp. 1983. Cooling gradients across pens in a finishing piggery. J. Agric. Eng. Res. 28:247-257.
  106. Ricalde, R. H. and I. J. Lean. 2002. Effect of feed intake during pregnancy on productive performance and grazing behaviour of primiparous sows kept in an outdoor system under tropical conditions. Livest. Prod. Sci. 77:13-21
  107. Rodriguez-Vivas, L., A. Ortega-Pacheco, C. Y. Machain-Williams and R. Santos-Ricalde. 2001. Gastrointestinal parasites in sows kept in two production systems (indoor and outdoor) in the Mexican tropics. Livestock Research for Rural Development 13:1-9.
  108. Roepstorff, A. and K. D. Murrell. 1997a. Transmission dynamics of helminth parasites of pigs on continuous pasture: Ascaris suum and Trichuris suis. Intern. J. Parasitol. 27:563-572.
  109. Roepstorff, A. and K. D. Murrell. 1997b. Transmission dynamics of helminth parasites of pigs on continous pasture: Oesophagostomum dentatum and Hyostrongylus rubidus. Intern. J. Parasitol. 27:553-562.
  110. Roepstorff, A., K. D. Murrell, J. Boes and S. Petkevicius. 2001. Ecological influences on transmission rates of Ascaris suum to pigs on pastures. Vet. Parasitol. 101:143-153.
  111. Ruiz, J., R. Cava, T. Antequera, L. Martin, J. Ventanas and C. J. Lopez-Bote. 1998. Prediction of the feeding background of Iberian pigs using the fatty acid profile of subcutaneous, muscle and hepatic fat. Meat Sci. 49:155-163.
  112. Sans, P., G. Gandemer, C. Sanudo, B. Metro, I. Sierra and R. Darre. 1996. Growth performance and carcass, meat and adipose quality of Gascony pigs reared in outdoor conditions. Journees de la Recherche Porcine en France 28:131-136.
  113. Santos Ricalde, R. H. and I. J. Lean. 2002. Effect of feed intake during pregnancy on productive performance and grazing behaviour of primiparous sows kept in an outdoor system under tropical conditions. Livest. Prod. Sci. 77:13-21.
  114. Sather, A. P., S. D. M. Jones, A. L. Schaefer, J. Colyn and W. M. Robertson. 1997. Feedlot performance, carcass composition and meat quality of free-range reared pigs. Can. J. Anim. Sci. 77:225-232.
  115. Schoenherr, W. D., T. S. Stahly and G. L. Cromwell. 1989a. The effects of dietary fat and fibre addition on energy and nitrogen digestibility in lactating sows housed in a warm or hot environment. J. Anim. Sci. 67:473-481.
  116. Schoenherr, W. D., T. S. Stahly and G. L. Cromwell. 1989b. The effects of dietary fat or fibre addition on yield and composition of milk from sows housed in a warm or hot environment. J. Anim. Sci. 67:482-495.
  117. Sheppard, A. 1998. The structure of pig production in England and Wales. Special Studies in Agricultural Economics No.40, pp. 39.
  118. Simopoulos, A. P. 1991. Omega-3 fatty acids in health and disease and in growth and development. Am. Soc. Clin. Nutr. 54:438-463.
  119. Smith, H. J. 1979. Transmission of Oesophagostomum species in swine on pasture in the maritime provinces. Can. Vet. J. 20:184-185.
  120. Spitschak, K. 1997. Fruchtbarkeits- und Aufzuchtleistungen von Sauen mit Ferkeln in der Freilandhaltung. Arch. Tierz. Dummerstorf. 40:123-134.
  121. Stansbury, W. F., J. McGlone and L. F. Tribble. 1987. Effects of season, floor type, air temperature and snout coolers on sow and litter performance. J. Anim. Sci. 65:1507-1513.
  122. Stern, S. and N. Andresen. 2003. Performance, site preferences, foraging and excretory behaviour in relation to feed allowance of growing pigs on pasture. Livest. Prod. Sci. 79:257-265.
  123. Stolba, A. and D. G. M. Wood-Gush. 1984. The identification of behavioural key features and their incorporation into a housing design for pigs. Ann. Rech. Vet. 15:287-298.
  124. Stolba, A. and D. G. M. Wood-Gush. 1989. The behaviour of pigs in a semi-natural environment. Anim. Prod. 48:419-425.
  125. Studnitz, M. and K. H. Jensen. 2002. Expression of rooting motivation in gilts following different lengths of deprivation Appl. Anim. Behav. Sci. 76:203-213.
  126. Thamsborg, S. M., A. Roepstorff and M. Larsen. 1999. Integrated and biological control of parasites in organic and conventional production systems. Vet. Parasitol. 84:169-186.
  127. Thamsborg, S. M., R. J. Jorgensen, P. J. Waller and P. Nansen. 1996. The influence of stocking rate on gastrointestinal nematode infections of sheep over a two-year grazing period. Vet. Parasitol. 67:207-224.
  128. Thomsen, L. E., H. Mejer, S. Wendt, A. Roepstorff and O. Hindsbo. 2001. The influence of stocking rate on transmition of helminth parasites in pigs on permanent pasture during two consecutive summers. Vet. Parasitol. 99:129-146.
  129. Thornton, K. 1990. Outdoor Pig Production. Farming Press Ltd: Ipswich, UK.
  130. Tubbs, R. C., S. Hurd, D. Dargatz and G. Hill. 1993. Preweaning morbidity and mortality in the United States swine herd. Swine Health and Prod. 1:21-28.
  131. Van Putten, G. 1978. Comfort behaviour in pigs: informative for their well-being. In: Proceedings of the 28th Annual Meeting, European Association for Animal Production, Brussels Belgium, August, 1977. pp. 70-76.
  132. Vidal, J. M., S. A. Edwards, O. MacPherson, P. R. English and A. G. Taylor. 1991. Effect of environmental temperature on dietary selection in lactating sows. Anim. Prod. 52:597 (abstract).
  133. Vieuille, C., F. Berger, G. Le Pape and D. Bellanger. 2003. Sow behaviour involved in the crushing of piglets in outdoor farrowing huts-a brief report. Appl. Anim. Behav. Sci. 80:109-115.
  134. Waldrop, P. W., R. J. Mitchell, J. R. Payne and K. R. Hazen. 1976. Performance of chicks fed diets formulated to minimize excess levels of essential amino acids. Poul. Sci. 55:243.
  135. Wallace, H. D., G. E. Combs, Jr. and C. E. Haines. 1957. The influence of cooling growing-finishing swine on gains and feed conversion. Fla. Agr. Exp. Stat. Mimeo. Series 58-3.
  136. Warriss, P. D., S. C. Kestin and J. M. Robinson. 1983. A note on the influence of rearing environment on meat quality in pigs. Meat Sci. 9:271-279.
  137. Webster, S. 1997. Behavioural effects of outdoor and indoor rearing of pig: Observations on commercial units. Cambac JMA Research, UK.
  138. Webster, S. and M. Dawkins. 2000. The post-weaning behaviour of indoor-bred and outdoor-bred pigs. Anim. Sci. 71:265-271.
  139. Williams, J. R., B. J. Chambers, A. R. Hartley, S. Ellis and H. J. Guise. 2000. Nitrogen losses from outdoor pig farming systems. Soil Use and Manag. 16:237-243.
  140. Wood-Gush, D. G. M. and A. Stolba. 1982. Behaviour of pigs and the design of a new housing system. Applied Anim. Ethol. 8:583-584.
  141. Worthington, T. R. and P. W. Danks. 1992. Nitrate leaching and intensive outdoor pig production. Soil Use and Management 8:56-60.
  142. Wulbers-Mindermann, M. B. Algers, C. Berg, N. Lundeheim and J. Sigvardsson. 2002. Primiparous and multiparous maternal ability in sows in relation to indoor and outdoor farrowing systems. Livest. Prod. Sci. 73:285-297.
  143. Zihlmann, U., P. Weisskopf, H. Menzi and U. Ingold. 1997. Impacts of outdoor pigs on the soil. Agrarforschung 4:459-462.

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