Short-term choice of fattening pigs for additional plant-based materials
A major problem in conventional pig production systems is the occurrence of abnormal behaviours such as tail biting. Tail biting is a multifactorial problem, but it seems that a lack of proper enrichment materials prevents the animals from performing normal species-specific behaviour, e.g., rooting, nosing or chewing, and thus increases the prevalence of tail biting. The aim of this study was to identify plant-based enrichment material and nutritive additives that are attractive to pigs and that can be used as enrichment in practice. Therefore, we carried out two choice tests to investigate (i) which plant-based enrichment materials, differing in structure and flavour, pigs prefer and (ii) what kind of nutritive additives can be used to further increase the attractiveness of plant-based enrichment materials. In each choice test, pigs had the choice of six offered options. Pigs were tested individually in their familiar environment in an arena for 150 sec. The first choice test revealed that pelletized materials, i.e., lucerne pellets and straw pellets, were preferred over all other options tested (Friedman test, n = 55, p < 0.001). In the second choice test, the pigs’ interest was highest for the largest nutritive additive, i.e., maize kernels, compared to the other options tested (Friedman test, n = 65, p < 0.001). When choosing enrichment materials for pigs, structure, size and flavour should be considered. Pelletized plant-based enrichment materials or non-pelletized materials with nutritive additives can be recommended to stimulate exploration. Further studies should examine the interval at which enrichment material needs to be altered to keep pigs’ interest at a high level.