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

SIMPLE SUMMARY: There are several animal welfare concerns in farmed mink, including the occurrence of wounds, such as tail tip lesions. However, little is known about how these lesions develop. An increasing tendency to develop tail tip wounds was reported by Norwegian mink farmers after the introduction of multilevel cages. It appears that the mink jump directly at a presumably high speed from the upper level towards the nest box on ground level, causing the tail to hit the wire mesh several times. This study investigates whether cage design may be involved in the development of tail tip lesions. Specifically, effects of installing an additional hammock in standard multilevel cages, 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 in 600 mink at three farms (300 with hammocks and 300 without hammocks). More tail tip lesions were found in mink housed in cages without a hammock. Further studies are needed to understand the causal relationship between cage design and tail tip lesions in mink, in order to develop recommendations for improved cage designs and thereby improving animal welfare. ABSTRACT: 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.