Mixing feed in compost increases use but not cleanliness of rooting areas for growing-finishing pigs

Providing pigs with a rooting area filled with an appropriate material enables exploratory behaviour and is therefore considered to improve animal welfare. Mixing corn pellets into the rooting material could increase use and exploration while reducing elimination behaviour in these areas. To investigate this hypothesis, we compared two experimental pens (E) with rooting areas filled with compost produced from garden waste, in which 2 kg of corn pellets were mixed into every morning, with two control pens (C, rooting areas filled with compost only) on a commercial farm. Groups were repeated to obtain six replicates per treatment. We registered behaviour once a week through direct observations of the complete outdoor area and additional video recordings of the rooting area. Behavioural variables were general activity, rooting, agonistic and play behaviour. Cleanliness of the rooting material was assessed via visual scoring and chemical analysis of compost samples. The latter included tests on dry matter content, conductivity, and ammonium concentration. Data were analysed with linear mixed-effects models. Results showed that there was a tendency for a higher total number of pigs in the rooting area in E than in C (P=0.06). In E, more pigs were lying in the rooting area than in C (P=0.04). There was no difference in activity and rooting behaviour between treatments. Daytime influenced all recorded behaviours in the rooting area (P<0.001). Conductivity and ammonium concentration in the compost increased the longer the compost remained in the rooting area (P