1 Department of Animal Science - Behaviour and stressbiology, Department of Animal Science, Science and Technology, Aarhus University2 Science and Technology Learning Lab, Science and Technology, Aarhus University3 Department of Biomedical Sciences, University of Veterinary Medicine, Vienna4 Department of Animal Science - Behaviour and stressbiology, Department of Animal Science, Science and Technology, Aarhus University5 Science and Technology Learning Lab, Science and Technology, Aarhus University
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.