How is feed-related behaviour in growing pigs affected by total mixed ration feed with intensively treated silage?

Abstract: In Nordic countries, roughage e.g. silage from ley crops is mainly provided in the daily feed rations to pigs within organic production systems. Grass-clover silage brings multiple advantages in letting pigs perform natural behaviours and reduces aggressive social interactions. Although, pigs’ consumption of roughages such as silage varies and thus affect the nutrient utilization and their behaviour. The aimof this study was to examine feed-related behaviours in growing pigs fed total mixed ration (TMR) diets with inclusion of either chopped and intensively treated silage or solely chopped silage. In total 64 growing female and immuno-castrated male pigs (Yorkshire x Hampshire), thus 32 pigs from two batches (40 and 80 kg live weight), were included in the study and divided into four groups of eight pigs per pen in each stable. Two groups of pigs from each batch were fed treatment SI where the silage had been chopped and thereafter intensively treated in a bio-extruder, while two groups were fed treatment SC where the silage had been chopped with no further treatment. Pigs were observed for two days per batch by direct observations three times per day, in the morning prior to and after feeding, in the middle of the day separate from feeding, and in the afternoon prior to and after feeding. Data was collected by instantaneous (scan) and continuous sampling to estimate feed-related behaviours and social interactions. Statistical analyses were performed using Minitab 18 and pigs’ behaviour differences were analysed with ANOVA using general linear models. Pigs in treatment SI were eating from the feed trough more frequent (p < 0.01) while pigs in treatment SC spent a greater extent on rooting behaviour (p < 0.01). After feeding and separate from feeding, SC pigs were more active compared with SI pigs (p = 0.003 and p = 0.002, respectively). Weight of the pigs did not have any clear effect on feed-related behaviours or social interactions (n.s), however 80 kg pigs were more active before feeding (p = 0.05). Based on the results of this study, pigs seemed to spend longer time eating, presumably also with greater feed consumption, when fed TMR with inclusion of intensively treated silage. This feeding strategy might therefore benefit the nutrient utilization from silage and have a positive effect on pig behaviour in growing pigs.