Growing interest of the public in animal welfare issues may in the future lead to a ban on farrowing crates. Development of farrowing pens are therefore needed. Pens that on the one hand side can meet the public and consumers' demand for more welfare friendly housing of farrowing sows and on the other hand side meet the pig producers' demand for an efficient production with low piglet mortality at a low cost.

The birth process itself is one of the largest challenges of the yet unborn piglet. Stillborn piglets have often suffered from lack of oxygen during birth due to prolonged farrowing. Stress of the periparturient sows may be a major contributor to prolonged farrowings. A way to reduce birth problems and thus reduce the number of stillborn piglets may thus be to limit typical stressors around parturition. Two such are when the sows are introduced to the farrowing pen close to the time of farrowing and/or if sows are moved to crates from a loose housing gestation system.

Late introduction and crating may also influence maternal behaviour and maternal behaviour may influence the risk of crushing. Pedersen and Jensen (2008) investigated the influence of late versus early introduction to farrowing pens on the progress of parturition and on maternal behaviour. The late introduced sows were not moved to the farrowing pen until day 114 of pregnancy whereas the early moved sows were moved no later than 10 days before expected parturition. The only significant difference found was that sows introduced late showed more postural changes during nest building than sows introduced early whereas there was no effect on maternal behaviour of importance for crushing after birth. Pedersen and Jensen (2008) also investigated if late introduction affected parturition and maternal behaviour more or less when sows were moved to pens compared to crates. The results were clear. The primiparous crated sows had longer birth intervals and more stillborn piglets when moved late to crates compared to pens. This was not the case for multiparous sow experienced with crating from previous farrowings. Thus crating of sows introduced late has negative effects on the progress of parturition and the risk of stillborn piglets, most likely since they experience crating for the first time in their life.

* "Establishment of floor heating can save piglets."

Besides stillbirth, hypothermia and starvation are other major causes of mortality. These causes of death may also be influenced by features in the pen environment. In order to find ways to reduce hypothermia at birth, aspects of the microclimate at the birth site need to be investigated. For newborn piglets, heat loss is very critical. In order to prevent this heat loss all farrowing pens are equipped with a heated creep area away from the sow. The piglets however tend to stay close to the sow's udder to get colostrum and the consequence is that they do not stay in the creep area until a few days after farrowing (Hrupka et al., 2000a,b). However, at this time, heat loss is less critical for their survival.

Malmkvist et al (2006) therefore investigated if neonatal survival could be increased by heating up the floor in the whole pen area during the first critical two days of life. The floor was heated from 10 hours into the nest-building phase and the heat was turned off two days after birth of the first piglet. Since this may cause heat stress of the sows, it was also investigated if floor heating affected stress hormones, oxytocin, the birth process and neonatal viability at birth (Damgaarid et al., 2008; Malmkvist et al., submitted). The results showed that in pens with floor heating, earlier establishment of normal body temperature after birth took place. The normal drop in temperature right after birth recovered faster in the piglets born on the heated floor. The piglets with heated floor also had an earlier colostrum uptake. The time taken before all 15 piglets had suckled for the first time was shorter in piglets with heated floor than without. Also mortality was reduced from 2.6 piglets per litter in pens without floor heating to 1.4 piglet per litter with floor heating. However, when using full floor heating, sows had increased cortisol during parturition, whereas neither oxytocin, the birth process nor neonatal piglet viability were affected. To avoid any negative effect of heat stress, only part of the pen should be heated. This is possible when the sow is loose and can choose herself where to lie. However, to be of any help to the piglets, the sows must choose to farrow on the heated floor.

Pedersen et al. (2007) therefore investigated if floor heating affected the sow's choice of nesting area in pens with partly heated floor. These pens were divided into a dunging/activity area and a resting area that could be heated or left neutral. The results showed that an equal number of sows farrowed in the two areas. The sow's choice of nest site was not affected by heating of the resting area. However, after farrowing the sows chose to lie more in the resting area when the floor was heated compared to when the floor was unheated, which indicates that the heated floor was not aversive to the sows during parturition.

It was therefore concluded that establishment of floor heating can save piglets. However, if the floor is only heated in zones, it is necessary to make this area attractive as resting area using other pen features in order to assure that the piglets are born in the heated area.

It has been shown that support during lying down events reduced the risk of piglets being crushed. Marchant et al. (2001) showed that the risk of crushing was only 0.5 per cent when the sows used support compared to 14 per cent during unsupported lying down events. Thus, pen features that may reduce crushing has to allow the sow to lie down using support. The question is then how to develop pens that minimise the occurrence of unsupported lying down events.

Many pens are equipped with so called farrowing rails that prevent the sows from crushing the piglet against the wall when lying down. In a choice experiment, Damm et al. (2006) showed that sows actually avoided lying down against walls equipped with rails whereas they preferred solid walls. By using sloping walls instead of rails, it may be possible to avoid many of the unsupported lying events that are risky for the piglets and at the same time the walls still have the same function as the farrowing rails in preventing the sows from crushing the piglets against the wall when lying down there. An attractive lying wall may at the same time be able to guide the sow to lie in a certain part of the pen that contains good pen features for the piglets, for example floor heating as mentioned earlier.

Another way to attract the sows to a specific nest area may be to isolate part of the pen in that sows may prefer to nest in enclosed areas. This was investigated by Damm et al. (submitted). Half of the pen area was covered by a roof of artificial leaves and the other half was left open. They observed if sows preferred to nest build and farrow under the roof. There was a strong tendency for the sows to farrow under the cover, however, the effect was not significant. They also showed that the choice of nest site was unaffected by access to straw. Even though sows did not show a strong motivation to farrow under the cover, the experiment did show that sows choose a specific nest site in the pen where they stay continuously during the first 24 hours after parturition.

It was therefore concluded that sows do divide the pen into zones if given the opportunity but the choice of nest site was only mildly affected by nest covering. However other types of isolation or nest cover may be more attractive and further investigations are needed.

* "It has been shown that support during lying down events reduced the risk of piglets being crushed."

The occurrence of risky behaviour for crushing in relation to straw was also investigated. Many studies have shown that sows are highly motivated to nest build (Jarvis et al., 2001). It is known that high activity during the nesting phases is related to low risk of crushing (Andersen et al., 2005, Pedersen et al., 2006), and that access to straw can stimulate activity during nest building (Thodberg et al., 1999. Damm et al., submitted) showed that the number of near-crushing situations was reduced in sows that had free access to straw. Herskin et al. (1998) found that sows were calmer during parturition when given access to straw and Pedersen et al. (2003) showed that feedback from a nest resulted in earlier colostrum uptake by the piglets. Pedersen and Damm (unpublished) investigated the amount of straw used by sows before, during and after nest building. They showed that sows removed on average 0.5 kg long straw from a rack daily before farrowing and on the days after farrowing. On the day of nest building, they removed on average 2 kg straw ranging from below 0.5 kg to 7.6 kg. per sow.

According to EU legislation, sows must be given access to suitable nesting materials unless the dunging systems prevents this. However due to the above mentioned positive effects of straw, it must be recommended that new farrowing pens are designed in a way that allows the use of more than 2 kg. long straw during the days around farrowing.

In order to prevent crushing and assure good access to the sow's udder, it is also important that there is space enough in the pen for the sow to lie down freely and for the piglets to nurse undisturbed at the udder and rest in the heated creep area. Moustsens and Poulsen (2004 a,b) and Moustsen et al. (2004) therefore measured the physical dimension of 368 sows and piglets. The length (95 per cent quantile: 200 cm), shoulder (95 per cent quantile: 47 cm) and depth (95 per cent quantile: 71 cm) of the sows and piglets was measured and it turned out that today's sows are both heavier and longer than for 15 years ago. Besides the dimension of the sows, the space they need for lying down and getting up should also be considered. These were estimated to an average of 32 cm in width and 16 cm in length (Moustsen and Duus, 2006).

* "The creep area needs to be at least 1.3 square metres [which is] much larger than today's creep areas."

These space requirements should be included in new pen designs in order to allow free movements of the sows during lying down, getting up and turning around. The space for the piglets should allow free access to the sow's udder. The length of the piglets at four weeks of age was on average 56 cm. The lying area should therefore allow space enough for the sow to lie laterally plus the length of a piglet, which equals at least 134 cm. The space of the heated creep area should allow at least 10 piglets to lie in partly lateral position at five weeks of age. To allow this, the creep area needs to be at least 1.3 square metres. This is much larger than today's creep areas that are usually around 0.4 to 0.6 square metres. The new pens should be designed to incorporate enough space in the creep area for all piglets and space enough to allow piglets' free access to the udder.

Conclusions

Based on this series of experiments on pen features and established knowledge the next step has been to design prototype pens that incorporate all the pen features found important for sows and piglets (Moustsen et al., 2008a,b).

Four areas of interest were identified as important to consider in farrowing pen designs. These are, besides the sow and piglets, the hygiene that would be improved through a slatted floor area. Thus, the pens should ensure that the sows use this area for dunging and not for nesting and resting.

Also, the ease at which management can be performed should be considered. The pens should allow easy access to the piglets from outside the pens and should be equipped with pen features that can protect the handler from the sow during handling of the piglets.

Finally, the pens should be incorporated in the building in a way that minimises unused space in the house in order to reduce building cost.

References

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Further Reading

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May 2009