The revised brochure on environmental enrichment and nest-building material for pigs sets out the criteria for enrichment material in the sty in more concrete terms. One of the key principles is meeting the pig’s need to root and explore. But sows have another equally important behavioural need in which environmental enrichment plays a role: the instinct to build a nest.

FROM WILD BOAR TO FARM ANIMAL

Domestic pigs are descended from the European wild boar. In the wild, when she’s about to give birth, a female boar separates herself from the group and finds a sheltered spot out of the wind. She builds a nest from branches, leaves and other plant material, forming a hollow where her piglets are born. The nest keeps the piglets close together and protects them from the cold and predators. But humans have been keeping pigs for thousands of years. Surely little remains of this primal behaviour in the domesticated sow by now. Or does it?

INSTINCTIVE BEHAVIOUR

It’s a question that fascinated researcher Anita Hoofs from Wageningen University & Research. She wanted to know how much of this original nest-building behaviour remains in the modern sow. In 2012, she studied a sow that had already farrowed three litters in a conventional maternity pen without any nesting material. In a research setting, the sow was offered a range of materials, including jute cloths and short and long straw. Cameras tracked her behaviour closely. For the first five days, very little happened. The sow lay quietly and seemed completely uninterested in the materials. Then, the night before she was expected to give birth, something suddenly changed. A surge of hormones spurred her into action.

CALMER FARROWING

The sow began pulling apart a bale of straw and gathering the material together. Using her snout and trotters, she pushed the straw into a heap and hollowed out a dip in it, exactly as wild boar would do. Then she went looking for softer materials, dragging jute cloths over to the nest one by one to line it. Finally, she carefully rearranged everything again, and only when the nest was finished did she begin to farrow. ‘She did exactly what a wild boar would do,’ says Hoofs. ‘That behaviour is so deeply rooted in the pig’s brain that it comes back, even after generations of domestication.’ Allowing a sow the opportunity to nest has clear benefits. The sow is calmer, and farrowing progresses more quickly. ‘We observed that farrowing often goes more smoothly when sows can act on their nesting instinct. And a calmer farrowing process can also help ensure that all the piglets get a more equal share of the colostrum.’

THE RIGHT MATERIAL IN THE RIGHT PLACE

Providing jute cloths as nesting material has been compulsory across KDV since 2012. The benefits for both sows and piglets are clear, and KDV’s early adoption put it well ahead of the rest of the sector. The updated brochure Environmental Enrichment and Nest-Building Material for Pigs (Hokverrijking en nestbouwmateriaal voor varkens) now makes the provision of nesting material compulsory for all pig farmers. As with enrichment materials provided in the pen, nesting material only counts if the animals can actually engage with it. The material must be manipulable and preferably available on the floor so the sow can dig at it with her snout and trotters and pick it up in her mouth. Consideration should be given to where it is placed. If the material is hung too close to the feeder, for example, the sow could drag it into the trough because, to her, it looks like a good place for a nest. Timing is also important. The regulations require nesting material to be available at least one week before farrowing. In practice, a sow will usually only start to actively use it about a day before she gives birth. When a sow starts manipulating jute cloths or straw, farrowing is likely to be imminent.

ENRICHMENT IN THE FIRST FEW WEEKS

Enrichment materials should also be available in the pen after farrowing. Suckling piglets need to learn to eat solid feed while their teeth are coming through. Materials such as jute cloths, ropes or other manipulable items encourage piglets to explore, but also to bite and chew. Chewing stimulates saliva production and can make the transition to solid feed easier. ‘In this phase, it’s actually better to give them a bit too much enrichment than too little,’ says Hoofs. ‘Piglet behaviour is highly synchronised. When one piglet starts to play with something, their littermates will often join in.’ But the most important factor for success is the sow herself. If the first few weeks go well and she’s able to care for her piglets properly, everything else generally follows on naturally. Catering to her species-specific needs is always worthwhile.