Introduction
Gestation sow housing remains a controversial issue today. In a variety of empirical and theoretical scholarly works, the advantages and disadvantages of three types of pregnant sow housing have been assessed and debated with regard to animal welfare and production outcomes. Even though more and more scholars and practitioners alike tend to recognize the benefits of the group housing, this view has not been universally accepted. Den Hartog et al. asserted that the “productivity of stalled sows is equal to or somewhat better than that of sows housed in groups during pregnancy (den Hartog, Bachus, & Vermeer, 1993, p.1343).” What’s more, controversial data has been obtained with reference to various subtypes of group pen housing of pregnant sows. MAIN CLAIM: Despite its flaws, group housing provides the biggest number of benefits to gestation sow, and therefore it should generally be accepted as the housing of choice.

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Cons
The disadvantages of all three housing types have been discussed by Rhodes et al. (2005) and, more recently, by the American Veterinary Medical Association Animal Welfare Division (2014). Rhodes’ et al. (2005) comprehensive overview has not exposed any notable differences in physiological stress between the pregnant sows placed in stall housing and those in group housing. Moreover, they have found that tethers and stalls had a nearly similar effect on the pregnant sows’ behavior. Still, the disadvantages of placing pregnant sows in individual stalls included the restricted freedom of movement, which prevents sows from forming community nests, enjoying the complexity of the environment, getting a better regulation of body temperature, and engaging in varied behavior including play. Further, stall- housed sows have been found more likely to display stereotypic behavior, “a repeated, relatively invariant sequence of movements which has no obvious purpose” (Rhodes et al., 2005, p. 1584). In group-housed sows, aggression was a significant disadvantage, especially when sows are kept in extensive groups needed for the use of electronic saw feeders in an economically viable manner or when new sows were introduced to form groups. Another disadvantage of keeping sows in stalls is that they are unable to exercise control over their interactions with the environment. Plus, a disadvantage of group housing is that it places sows at a higher risk of injury in comparison with stalls. As for farrowing, lower farrowing rates have been observed in sows housed in stalls. The conclusions of the American Veterinary Medical Association Animal Welfare Division (2014) with regard to disadvantages of every gestation sow housing type have sometimes converged and sometimes diverged from the results of Rhodes et al. (2005). The following data has been added with regarding to the key flaws of each type of housing: the risk of injuries (associated with confinement) among sows was the highest in animals housed in stalls; stereotypies are more likely to develop in sows housed in individual stalls; group aggression may cause the greatest number of injuries and may lead to either overweight or underweight depending on the level of dominance of sows in a group; the greatest danger of parasites and encounters with harmful environmental materials is in free-range housed sows.

Pros
Now, each type of housing gestation sow has been found to have its advantages based on Rhodes et al. (2005) and the American Veterinary Medical Association Animal Welfare Division (2014). Specifically, group and free-range housing provide sows with such important advantages as foraging opportunities, increased social interactions, increased movement, and better behavior patterns (with regard to stereotypies). Other clear advantages of group and free-range housing for pregnant sows include: a reduced accumulation of ammonia due to the reduced noise because of the exposure to the environment, greater behavioral opportunities, higher farrowing rates, and improved regulation of the temperature of the body. Next, keeping sows in individual pens has its own advantages as well: the individual access to resources, better accessibility to the animal, and protection from aggression.

Solution
Even though Rhodes et al. (2005) and the American Veterinary Medical Association Animal Welfare Division (2014) do not explicitly emphasize the advantages of one type of housing over another, they provide sufficient evidence to claim that keeping pregnant sows in individual pens deprives the animals of significant advantages associated with the other two housing types. Exploration of further research provides more evidence in support of this view. In particular, from the empirical research by Vieuille-Thomas, Le Pape, & Signoret (1995), one can learn that stall-housed gestation sows are far more likely to develop stereotypies than sows housed in groups. They found that “the proportion of sows developing stereotypies did not differ between stall-housed and tethered females (89.5 vs. 94.1%), but was lower in group-housed compared with stall-housed sows (66.2 vs. 92.6%) (Vieuille-Thomas, Le Pape, & Signoret,1995, p.19). Also, from the research by Chapinal, de la Torre, Cerisuelo, Casa, Baucells, Coma, Vidal, & Manteca (2010), one can learn that group housing provides significant advantages in that it reduces stress levels for sows and increases their welfare. The scholars explain that since stereotypies are considered to be markers of poor welfare in animals as “they develop in the situations of stress, frustration, or lack of control,” the decrease in stereotypies reflects the increased ability of animals to cope with the environment. As for group housing and free access housing, no significant differences have been found with regard to prevalence of claw lesions and lameness. It has led the scientists to believe that “further investigation on risk factors of locomotor disorders in sows is necessary” especially “given that group housing for gestating sows will become mandatory in the EU from 2013 onwards” (Pluym et al., 2011, 101).

Conclusion
In conclusion, group housing and free-range housing have clear advantages over the individual pen housing because they ensure increased animal welfare. At the same time, group housing, the more accessible of the two, needs to be further researched with regard to its subtypes and further improved since it has important flaws (such as aggression and injuries).

    References
  • Chapinal, N., de la Torre, L., Cerisuelo, A., Gasa, J., Baucells, M., Coma, J., Vidal, A., & Manteca, X. (2010). Evaluation of welfare and productivity in pregnant sows kept in stalls or in 2 different group housing systems. Journal of Veterinary Behavior: Clinical Applications and Research, 5 (2), 82–93.
  • Den Hartog, L., Backus, G., & Vermeer, H. (1993). Evaluation of housing systems for sows. J. Anim. Sci., 71, 1339-1344.
  • Pluym, L., Van Nuffel, A.,  Dewulf, J., Cools, A.,  Vangroenweghe, S., Van Hoorebeke, S. & Maes, D. (2011). Prevalence and risk factors of claw lesions and lameness in pregnant sows in two types of group housing. Vet. Med., 56,101–109.
  • Rhodes, R.T., Appleby, M.C., Chinn, K., Douglas, L., Firkins, L.D., Houpt, K.A., Irwin, C., McGlone, J.J., Sundberg, P., Tokach, L., & Wills, R.W. (2005). A comprehensive review of housing for pregnant sows. J Am Vet Med Assoc., 227(10),1580-90.
  • Vieuille-Thomas, C., Le Pape, G. and Signoret, I.P. (1995) Stereotypies in pregnant sows: indications of influence of the housing system on the patterns expressed by the animals. Applied Animal Behavior Science, 44, 19-27.