Some enrichment materials also help reduce tail and ear biting.
All pigs have a strong inborn need to chew and root. Many of the behavioural problems in pig farming, such as tail and ear biting, are partly due to the scarcity of chewable and rootable materials on most commercial pig farms. In such environments, the urge to chew can easily be redirected to pen mates.
The objects and materials given to pigs in commercial farming vary greatly in their efficacy in reducing biting and improving welfare. Some of the commonly used enrichment objects are actually quite inefficient. On the other hand, the best types of enrichment provide substantial benefits to farmers and pigs alike. It is therefore of interest to the farmer to know which types of enrichment have both a real beneficial impact and low costs.
Locations in the pen affect efficacy
The same material can be either efficient or inefficient as enrichment, depending on how it is used.
Pigs have an inborn urge to use different locations for eating, sleeping and toileting. In intensive farming, the limited size of the pens and the high density of animals makes this a challenge, and the distinction can get disrupted. For this reason, enrichment materials and objects have to be placed in a way that supports this natural division of pen space, instead of further blurring it. There are some research results suggesting that plant-derived materials, such as fresh wood and ropes of natural fibre, may be associated to a sleeping area in a pig's mind, especially when they are located on or near the floor. Objects made of metal and plastic, on the other hand, seem to be better to place on the slatted floor, because pigs easily urinate and defecate near them.
It is important to have enough material or objects. One object for ten pigs provides only very little benefit. While the object still is new, all the pigs try to use it at the same time. Later, too, it often happens that seeing one pig chewing on the objects arouses the interest of others to do the same. The number and locations of objects therefore have to be planned so that as many pigs as possible can easily use them at the same time.
Tails can be kept undocked
The right kind of enrichment helps reduce tail biting. To fully prevent tail biting, however, it is necessary to ensure that the other crucial factors also are taken care of. In addition to chewable and rootable materials, the important factors include e.g. the right composition of feed (in terms of protein and mineral content, amino acids etc.), a sufficient amount of fibre in the feed, sufficient feeding space to allow all pigs in the pen to easily eat at the same time, continuous access to drinking water, a suitable ambient temperature, good air quality and the absence of draught.
Materials and objects suitable for chewing and rooting are often called enrichment or toys. These words are handy to use but a bit misleading. Toys may sound like a luxury, but pigs have such a strong inborn need to chew and root that they actually are a necessity.
Tail and ear biting, resulting in damage, are not part of the natural behaviour of pigs. They are abnormal behaviours caused by problems in the living conditions. Some of the most common causes include insufficient fibre content of the feed, limiting the amount of available drinking water, poor air quality and scarcity of materials to chew on.
Pigs like to act together. The usefulness of enrichment objects can be increased by designing them to be large enough for two or three pigs to use at the same time.
In the EU, the minimum standards of pig husbandry are defined in Council Directive 2008/120/EC. Regarding enrichment, the EU legislation states that pigs must have permanent access to a sufficient quantity of material to enable proper investigation and manipulation activities. Each EU country has its own definisions as to what is considered sufficient by the legislators of that country. The description below refers to the legislation in Finland.
The government decree on the protection of pigs, 13 §, states that pigs must have continuous access to a sufficient quantity of material that is safe for the health of the animals and with which the animals can fulfil their species-specific behavioural needs, such as rooting and exploration.
The detailed definition of the meaning of this law has been stated by the Finnish Food Safety Authority Evira as follows: "Pigs must have wood shavings, sawdust, peat, straw or similar material in a quantity that makes it possible to form small mounds of the material. If such a quantity is not feasible (for example due to blocking the manure removal system), pigs must have continuous access to "toys" (balls, chains etc.), and it is recommended that toys are changed from time to time. When using toys, twice a day pigs also must be given some straw, hay, newspapers or other material suitable for manipulation, to fulfil the pigs' need to chew and root."