“…Object manipulation is affected by space, other enrichment materials offered to pigs, (Larsen et al, 2019;van de Weerd et al, 2009) and the position of it (Scott et al, 2009;Larsen et al, 2019;Dalmau et al, 2019). Object manipulation diminishes by time as pigs become habituated to them and as aging changes their choices (Trickett et al, 2009;van de Weerd et al, 2009;Dalmau et al, 2019) while the variation of enrichment materials does not seem to have a significant effect in reducing tail biting severity (Chou et al, 2019a). Cleanliness plays a role (Averos et al, 2010) but everyday cleaning or replacement doesn't seem to have an effect on attractiveness for short periods (Beaudoin et al, 2019).…”