Feed restriction and tubes for environmental enrichment in growing mink—Consequences for behaviour and welfare

Tail Tip Lesions in Mink (Neovison vison): Effects of an Additional Hammock in Multilevel Cages

The occurrence of wounds in different anatomical regions, such as tail tip lesions, is an important welfare concern in farmed mink. This study investigated whether mechanical factors attributed to cage design in multilevel cages may be involved in the etiology of tail tip lesions. Specifically, effects of an additional hammock intended to reduce speed during transitions between cage levels and thereby assumed to lower the incidence and severity of tails hitting the wire mesh were investigated. Three mink farms and a total of 600 mink participated in the study. On each farm, brown female mink (n = 100) were either housed in multilevel cages equipped with plastic hammocks (placed either perpendicular or parallel to the sidewalls) or in standard multilevel cages without hammocks (n = 100). The study was conducted from December to March using singly housed females. Significant differences in the number of tail tip wounds were found between groups with a hammock installed in the cage vs. control groups in two of the farms (p = 0.029 and p = 0.031), with more wounds developing in cages without a hammock. Furthermore, there was a trend towards difference in the number of tail tip wounds in groups with hammocks installed perpendicular vs. groups with hammocks installed parallel to the cage sidewalls, but a potential farm effect cannot be ruled out. This study is the first to suggest that mechanical factors associated with cage design may play a role in the etiology of tail tip lesions in farmed mink. Further studies are needed to understand the causal relationship between cage design and tail tip lesions in mink.

Responses of mink to auditory stimuli: prerequisites for applying the 'cognitive bias' approach

The aim of the study was to determine and validate prerequisites for applying a cognitive (judgement) bias approach to assessing welfare in farmed mink (Neovison vison). We investigated discrimination ability and associative learning ability using auditory cues. The mink (n=15 females) were divided into two groups (High, n=8; Low, n=7, representing the frequency of the tone they were habituated to, 18 and 2 kHz respectively) and were tested using a habituation-dishabituation procedure in experiment 1. In experiment 2 one auditory stimulus was followed by an inter-trial-interval (safe/neutral situation), whereas another auditory stimulus was followed by an aversive stimulus (air blow) before the inter-trial-interval (danger situation). We observed behaviour including latencies to show a response during both experiments. The High mink showed significant habituation in experiment 1 but the Low mink only showed habituation in experiment 2. Regardless of the frequency used (2 and 18 kHz), cues predicting the danger situation initially elicited slower responses compared to those predicting the safe situation but quickly became faster. Using auditory cues as discrimination stimuli for female farmed mink in a judgement bias approach would thus appear to be feasible. However several specific issues are to be considered in order to successfully adapt a cognitive bias approach to mink, and these are discussed.