Group housing of gestating sows supports production and welfare

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Group housing of gestating sows supports production and welfare


In 2013 in the Netherlands an individual housing of pregnant sows from four days after insemination until one week before farrowing was prohibited by EU legislation (Anonymous, 2008). All farmers had to change their operation scheme to meet the requirements of new regulations. Obviously number of researches was carried out to supply this decision

The benefits from group housing or individual housing were always contradiction issue (J.L.Barnett et al., 2001). The group housing is more natural for sows and allows them to express their natural behavior - build a nest, socially interact with other pigs. Therefore, it has to have a positive effect on health and performance of animals. On the other hand, mixing of pigs in group cause an agonistic behavior and can become a problem regarding to injuries in group and culling of animals as a consequence.


The group formation by mixing animals may lead to higher aggression at the first week of housing as a result of social ranking establishment in the group (Karlen et al., 2007) and later at the feeding competition. But already from the day 2-5 the declining of the cortisol (stress indicator) concentrations was observed (Karlen et al., 2007, Hemsworth et al., 2013). That implies that level of stress was lower due to established hierarchy. Moreover, the aggression tends to decrease at enlargement of space allowance per sow. Since more space becomes available submissive pigs are able to hide or escape from dominating ones (Hemsworth et al., 2013). Therefore, regarding to the group size it is necessary to take into consideration an optimal space allowance per sow. Nevertheless, research of Hemsworth et al. (2013) also indicates that once social ranking is established, the space per sow in group may be reduced. In addition, Mount and Seabrook (1993) suggest that aggressiveness may be reflection of sow personality. Thus, more research needed to concretize this suggestion which can be useful in sows’ selection.

The stereotypies – destructive behaviors - are also reflecting the welfare of pigs. This kind of behavior is related to stress situations, which animal cannot cope with. It also arises because of boredom and frustrating in animals. Chapinal et al. (2010) in their research established a fact that sows previously kept in stalls still show stereotypic behavior in group housing situation but it is observed in smaller extent which can be considered as an improvement in the welfare of sows.

Establishing hierarchy or fighting for food as well as escaping from aggressors may lead to injuries (Turner et al., 2006, Karlen et al., 2007). Occurrence of skin injuries reveals the aggression level presented in the group. Relatively small size of groups may decrease the offensive behavior and thus skin injuries frequency also (Hemsworth et al., 2013). Introduction of new animal in group results in increase of aggression and, therefore, lameness and claw injuries. Number of skin and claw injuries is in general higher in groups where sows are constantly mixed with new animals.

The stress caused by persistent aggression in group can negatively affect the reproduction performance of sows and development of embryo’s caused by unfavorable oviductal environment (Razdan et al., 2002). Especially, that becomes crucial while keeping sows together after insemination. Housing sow in crates during the gestation period was criticized by public. The main problem aspects describing this system were that animals do not have any social interaction and are restricted in exercise which causes them stress. According to Barnett and Hemsworth (1991) from 15 researches they studied, 8 appeared to show better reproduction performance under group housing conditions, the same time 4 of them showed better reproduction while sows were kept individually. In the study of Hansen and Kongsted (2002) group-housed sows characterized by very high litter size which can be accepted as an argument that group housing does not always lead to poor reproduction qualities. On the other hand research carried out in Australia in 1999 by Agribiz Engineering showed that number of piglets born alive by stall-housed sow was significantly higher.

There is also evidence that the housing of sows during gestation period has effect on their performance when they are kept in farrowing crates later. In the study of L.A. Boyle et al (2002) it is found that previously loose housed sows needed significantly less attempts to adapt and lie down in crates than sows used to confined housing. Thus, it is likely that loose housed sows developed sufficient fitness during their loose housing before being transferred to farrowing crates. That also led to lower lesion scores in loose housed sows. However, at the parturition the loose housed sows experienced more difficulties with lying down which resulted in higher lesion scores and might cause a piglet crushing (Baxter, 1984). It can be explained by more distinct expression of natural behavior of nest build before farrowing developed during loose housing of sows.

Also this study showed lower lameness at the late stage of gestation period among sows kept on deep litter in compare with stall-housed sows. That could be explained by deep littler bedding type and ability to move in the group pen in compare with stall-housed sows which were not able to walk and thus it was probably more difficult to identify the lameness in standing animals. Additionally, the straw bedding has decreasing effect on lameness occurrence (Svendsen, J. et al., 1992).

Interesting fact is that keeping pigs in the specific-stress-free (SSF) housing system when the stress is minimized by not transporting animals to other location or remixing groups has a positive effect on welfare and production of animals (Ekkel et al., 1995). It also means that providing all proper conditions required by pigs will diminish stress and, as a consequence, decrease the agonistic behavior in groups.


J.L. Barnett et al (2001) stated in the review of that problem that “it is the design of the housing system that is important to welfare rather than the housing system per se”. Summarizing all, the group housing as it was expected does have advantages as well as disadvantages. Such system affects sows positively in natural aspect; animals begin to express their natural behavior which supports one of aspects of animal welfare concept. But as it was mentioned in the discussion this issue stays controversial. Disadvantages of the group housing also have to be taken into account. The facts of discussion advise to consider searching for a compromise between group housing and stall housing. More research needs to be done to determine which housing type and on which stages of mating and gestation periods it could be applied so that it will be beneficial for sow’s health and its reproduction performance. Concerning the aggression in groups, larger space allowance per sow should be considered for diminishing of this type of behavior at least at the beginning when the establishing of hierarchy takes place. There is no unanimous opinion about positive effect of group housing on reproductive performance of sow, but some significant results demonstrate that there is a relation which cannot be ignored.

Therefore, pregnant sows can be group housed and it has its benefits, but for that farmer/stakeholder has to provide proper housing conditions and react on needs of the group promptly. This can be reached by engaging professionals with scientific background in decision making process.


  • Anonymous, 2008

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