Abstract
Since January 1 2013, group housing of sows has been compulsory within the European Union (EU) in all pig holdings with more than ten sows. Sows and gilts need to be kept in groups from 4 weeks after service to 1 week before the expected time of farrowing (Article 3(4) of Directive 2008/120/EC on the protection of pigs). The legislation regarding group housing was adopted already in 2001 and a long transitional period was allowed to give member states and producers enough time for adaptation. Even so, group housing of sows still seems to be uncommon in the EU, and is also uncommon in commercial pig farming systems in the rest of the world. In this review we share our experience of the Swedish 25 years of animal welfare legislation stipulating that sows must be loose-housed which de facto means group housed. The two most important concerns related to reproductive function among group-housed sows are the occurrence of lactational oestrus when sows are group-housed during lactation, and the stress that is associated with group housing during mating and gestation. Field and clinical observations in non-lactating, group-housed sows in Sweden suggest that by making basic facts known about the pig reproductive physiology related to mating, we might achieve application of efficient batch-wise breeding without pharmacological interventions. Group housing of lactating sows has some production disadvantages and somewhat lower productivity would likely have to be expected. Recordings of behavioural indicators in different housing systems suggest a lower welfare level in stalled animals compared with group-housed ones. However, there are no consistent effects on the reproductive performance associated with different housing systems. Experimental studies suggest that the most sensitive period, regarding disturbance of reproductive functions by external stressors, is the time around oestrus. We conclude that by keeping sows according to the pig welfare-friendly Directive 2008/120/EC, it is possible to combine group-housing of sows with good reproductive performance and productivity. However, substantially increased research and development is needed to optimize these systems.
Highlights
On January 1 2013, group housing of sows became compulsory in the European Union (EU) for animal welfare reasons
The Directive making group housing of sows compulsory within the EU in all pig holdings with more than ten sows stipulates that sows and gilts are to be kept in groups from 4 weeks after service to 1 week before the
The two most important concerns related to reproductive function among group-housed sows are: the occurrence of lactational oestrus when sows are grouphoused during lactation; and the stress that is associated with group housing during mating and gestation
Summary
On January 1 2013, group housing of sows became compulsory in the European Union (EU) for animal welfare reasons. During the 1990s, parallel to the development of the new management systems for loose-housed sows, the all-in-all-out systems for fatteners became more common in pig production in Sweden (see Table 1) This made it necessary to breed and subsequently wean a large number of sows within a short time. In a comprehensive study by Karlén et al [52] on welfare including reproduction in gestating sows in conventional stalls and in large groups on deep litter, sows on deep litter had a higher return to oestrus rate after mating. Challenges and research needs Our field and clinical observations suggest that by applying basic knowledge about the pig reproductive physiology related to mating, we can apply efficient batchwise breeding in non-lactating, group-housed sows with competitive herd productivity. Combination of experimental and field studies is a powerful approach in efforts to improve animal welfare, reproductive performance and economic productivity
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