Providing environmental enrichment may be an effective strategy to improve animal welfare by enabling positive affective (emotional) states and improving biological functioning, particularly where animals are confined indoors.
Poor animal welfare occurs where there is a mismatch between the animal’s needs and aspects of animal management and/or the animal’s environment. However, environmental enrichment alone will not address this mismatch. Good animal welfare relies on;
- meeting an animal’s physiological needs (e.g. good health, good nutrition, comfortable housing);
- good stockpersonship (e.g. low-stress animal handling, positive interactions);
- providing for pigs’ innate behavioural needs (e.g. the ability to carry out foraging behaviours such as nosing, rooting and chewing); and
- providing the opportunity to have positive experiences (e.g. through the ability to express play and social behaviour, to forage and explore, and, for sows, to express nesting behaviour and interact with their young).
What does environmental enrichment for pigs look like?
In order to satisfy a pig’s innate need to forage, enrichment needs to have certain properties, e.g. be ingestible, destructible, have a smell, and/or be chewable. For a pig to be interested in an enrichment material or object, it should be novel. Renewing and replacing objects and materials when they are no longer being used is essential to ensure pigs maintain interest and receive the benefits of the enrichment. Examples of enrichment objects include cotton cords, rubber strips, rope, wood, long branched chains, metal pipe, balls, edible enrichment block.
Providing substrate (i.e. surface materials) in which pigs can express foraging behaviour (exploratory activity directed at the ground involving rooting, grazing and exploring with the snout) is particularly important in indoor systems where tail biting and belly nosing can be reduced by providing preferred substrates such as hay, peat, mushroom compost, silage, sawdust and straw. Straw serves multiple purposes – bedding, nutrition, and enrichment. Straw may also reduce the frequency of undesirable behaviours such as aggression and tail biting. Long straw, rather than chopped straw, is more effective at reducing such behaviours as pigs are able to pick up and manipulate the long straw in their mouths. To maximise the positive impact of straw on exploratory behaviour, a minimum of around 250g of straw per pig per day is required (Pederson et al 2014).
Long straw elicits nest-building behaviour (consisting of pawing, rooting, pushing, carrying and arranging straw) in sows about to farrow as well as increases time spent lying down and reduces time spent performing stereotypic (abnormal, repetitive) behaviours in barren environments. Nest building is affected by the amount of straw provided to the sow. At least 2kg of long straw is recommended to satisfy the sow’s need to carry and manipulate materials for nest building (Baxter et al 2011). More straw as well as branches are required for a sow to be satisfied that she has built a ‘complete nest’. Housing systems should be designed to manage the beneficial impact of environmental enrichment on pigs, including the ability to manage provision of straw as bedding and manipulable material.