Usage of outdoor run and health aspects of fattening pigs fed whole plant vetch silage or straw as roughage

Advantages of feeding protein-rich whole plant silages in pig fattening, such as clover-grass silage, have been investigated in the past. However, vetch whole plant silage has not yet been under investigation. Vetch has many advantages from a crop production perspective and is a potential fibre- and protein-rich feedstuff for pigs. This study aimed to investigate if a) vetch silage compared to straw as roughage has positive effects on the outdoor run usage and the occurrence of foraging behaviour in the outdoor run, b) the duration of roughage intake and the amount of roughage consumed depends on the vetch species, and c) health aspects (skin lesions and lameness) are affected by the vetch silage compared to straw. A total of 120 mixed-sex fattening pigs [(Landrace × Large White) × Pietrain] were studied over two trials conducted throughout 11 months. In each trial, three dietary treatments were tested: silage made from Vicia sativa, silage made from Vicia pannonica, and straw as a control roughage. Each treatment included two groups of ten pigs per trial, resulting in 40 pigs per treatment. The roughage was offered to the animals in all groups from a rack in the outdoor run. The observation based on interval photos from video recordings of the outdoor runs. The usage of the outdoor runs and the display of different behaviours were determined on pen-basis by instantaneous scan sampling. Additionally, the time period until the silage was totally consumed was evaluated and twice a week silage leftovers were collected to estimate amounts of silage intake. The skin lesions of each pig were scored every week during the trial period according to the Welfare Quality® Assessment protocol. In December, the outdoor runs were used significantly more often in experimental groups, which were provided silage, than in the control groups, which were provided straw (p < 0.05). In May, the animals of the groups that received Vicia pannonica showed more frequent foraging behaviour than the animals of the control groups (p < 0.05). Neither the duration of silage intake nor the amount of consumed silage differed between the two experimental groups. Feeding vetch silage to fattening pigs had no effect on body lesions or the occurrence of lameness. The positive effect of vetch whole plant silage on outdoor run usage and foraging behaviour indicate that pigs are interested in this feedstuff, which can thus be an enrichment.