Any system of pig production affects the welfare of the pig. Most systems meet some of the requirements of the pig. For example, well managed intensive systems provide shelter, regulated temperature and ventilation, clean lying areas and adequate nutrition. However other aspects of the pig's requirements may be neglected such as provision of space to explore and for play behaviour, the desire to be in family social groups, and material to forage or root in. Pig production cannot exist if it is not economically viable hence commercial reality means pigs cannot be offered everything considered necessary for optimum welfare.
The role of research is to identify which aspects of the environment are most important to the pig and identify how these be incorporated into existing systems. This can only be achieved by understanding the behaviour of the pig. By knowing why an animal behaves in a certain way aspects of the environment can be prioritised and predictions can be made in relation to the welfare of the animal in novel systems. For example if space, fresh air and rooting are the most important elements to the pig then an outdoor extensive system should promote good welfare, however one small change, such as nose ringing the pigs, negates one of the main advantages of the outdoor system.
This paper describes a series of experiments which were devised to help understand growing pig behaviour and identify what is important to the pig. The aim of this research was to use the knowledge gained to develop a practical system which met the pigs' requirements and so would improve welfare.
In the initial studies pigs had various enriching stimuli and extra space. Pigs in enriched housing spent more time exploring and less time in harmful social and aggressive behaviour than pigs in pens with fully slatted floors and stocked at recommended space allowances. It was concluded that pigs in the absence of substrate to root, in redirect their rooting behaviour to penmates leading to harmful social and aggressive behaviour. However these pigs had four times the recommended space allowance, therefore the next experiment examined the effect of space allowance versus enriching the environment. Extra space did not improve welfare in commercial housing but enriching the environment improved welfare irrespective of space allowance.
The next question to be addressed was what substrate do pigs prefer to root in. A preference test was set up which offered pigs a choice of pairs of substrates. The pigs' choice was determined by the time spent using the substrate and showed that pigs prefer substances with a moisture content and texture similar to earth (eg peat and spent mushroom compost). Contrary to the popularly held view, pigs when given a choice do not prefer straw. The knowledge gained from this research was: pigs want to explore substrate, recommended space allowances are adequate and pigs prefer earth-like materials to root in.
The final part of this research programme was to incorporate this knowledge into commercial housing. The approach adopted was to suspend the enriching substrate (spent mushroom compost) on wire racks over the pigs. This meant the pigs could still be kept on slatted floors and no extra space was required to house the enriching substrate. The amount of harmful social behaviour performed by pigs was reduced by 25% in pens with the substrate and no pigs were tailbitten compared with 10% of pigs in the control treatment.
The inclusion of elements within any system can be prioritised to improve welfare by understanding what is important to the animal. This allows welfare to be improved while retaining systems which are economically viable in terms of animal production.