Additional foraging elements reduce abnormal behaviour – fur-chewing and stereotypic behaviour – in farmed mink (Neovison vison)

We investigated whether provision of additional appetitive and consummatory elements of foraging reduces baseline stress and abnormal behaviour – in terms of fur-chewing and stereotypic behaviour – in farmed mink. We studied 200 juveniles (n = 100 females and 100 males) during the 5-month growth period with plenty of feed, and subsequently the females as adults during the 2-month feed restriction period before mating. The mink were distributed in four equally sized groups: (i) FARM, conventional finely ground feed (<8 mm) without additional foraging elements; (ii) ROPE, access to biting ropes; (iii) CONS, chunky feed (parts up to 42 mm), replacing conventional feed; (iv) BOTH, access to both biting ropes and chunky feed. In growing mink, biting ropes reduced fur-chewing (P = 0.044) and chunky feed reduced stereotypic behaviour (P = 0.038) and fur-chewing in female mink (P = 0.019). During the season of feed restriction, the wear/tear of biting ropes increased. Females on the chunky diet had a higher concentration of faecal cortisol metabolites (P = 0.033), probably due to a more severe slimming resulting in a 6.2% lower body weight (P = 0.006) than the mink on the finely ground diet; still the chunky diet reduced time spent in pre-feeding stereotypies (P = 0.001). In the restrictively fed females, fur-chewing was reduced both by access to biting ropes (P = 0.005) and chunky feed (P = 0.007). Consequently, 54% of group FARM mink displayed fur-chewing compared to 21% in group BOTH. In conclusion, stereotypic behaviour was reduced by provision of chunky feed, increasing the consummatory element in daily foraging. Fur-chewing was reduced upon access to either biting ropes or chunky feed in female mink throughout the study. Our findings support frustrated foraging, mainly consummatory, behind abnormal behaviour.