Intensive free-range pig production on open grasslands has disadvantages in that it creates nutrient hotspots and little opportunity for pigs to seek shelter from the sun. Combining a perennial energy crop and pig production might benefit the environment and animal welfare because perennial energy crops like willow (Salix sp.) and Miscanthus offer the pigs protection from the sun while reducing nutrient leaching from pig excrements due to their deep rooting system. The objectives of this study were to evaluate how season and stocking density of pigs in a free-range system with zones of willow, Miscanthus and grass influence the behaviour of growing-finishing pigs, site preference for excretory behaviour, and damage to the energy crops. In total, 72 growing pigs were included in the two-season study with 36 pigs in each spring and autumn season. For each season the pigs were randomly assigned to six paddocks, which, in turn, were divided into high and low-density paddocks of 700 m2 and 2200 m2, i.e. 117 and 367 m2 per pig respectively. All paddocks were divided into seven different zones representing two zones with willow, two with grass, and one each with Miscanthus, cut Miscanthus (stubs) and a feeding area. Overall, ‘resting’ was the most frequent behaviour of all observations followed by ‘rooting’ with 54.4% and 19.3% of all behavioural observations, respectively. There were no main effects of stocking density for any of the behavioural elements. The excretory behaviour was significantly more pronounced in the zones with willows and especially the willow zone closest to the feeding area. On average, the pigs performed 49% of all excretions in this zone, although the zone only accounted for 15% of the total area. No significant interaction of excretory behaviour with zone and stocking density or season was found. Damage to the crops was very limited, even though most of the new Miscanthus shoots were eaten by the pigs in spring. Significantly more damage was caused to willow roots in high-density compared to low-density paddocks, but only in spring. Soil was found to be more turned over in the willow and grass zones closest to the feeding area than in the more distant zones, but only in spring. In conclusion, pig behaviour was not influenced by stocking density and pigs primarily performed the excretory behaviour in the willows and caused only limited damage to crops. Thus a combined production of pigs and energy crops is a feasible strategy to benefit both the environment and animal welfare.
Livestock Science, 2012, Vol 150, Issue 1-3, p. 200-208