cortisol levels in studies of group-housed females. Pain or social stress may also be why mink kits with bite wounds appear to grow more slowly than those without – although of course it may be that small body sizes cause animals to be bitten, rather than the other way around. Allowing the self-administration of analgesics and experimentally investigating minks’ social preferences could help explore this issue in the future. However, even without such detailed information, it seems valid to use wounds and scars as a sign of poor welfare in mink.
2WKHU DVSHFWV RI SK\VLFDO KHDOWK D %RG\ FRQGLWLRQ DQG FKDQJHV LQ ERG\ ZHLJKW Body weight SHU VH is probably of little welfare significance in mink; they are bred for large size, and are now far heavier than their wild counterparts. There are also genetic strain differences, with e.g. Blacks being lighter than Browns. Mink from large litters also tend to be smaller in adulthood which is an effect again unlikely to reflect welfare problems. However, changes in body weight and condition are likely to be important. For example, these are generally affected by chronic activation of the hypothalamicpituitary adrenal (HPA) axis in many species, and stressors can also reduce feeding rates and enhance catabolism. In mink themselves, exogenous cortisol is known to reduce kit growth rates, while dosing feed with tranquillizer (‘Mecibar’) from before birth until the age of eight to nine weeks resulted in kits having larger body weights at pelting. Kit growth rates have therefore often been used to assess welfare, and some relationships with other stress measures revealed. For example, small female mink kits have been shown to be more fearful than larger animals in ‘stick tests’. Stressors such as repeated immobilisation have also been shown to suppress minks’ feeding behaviour. Changes in body weight can also correlate with other signs of poor condition or welfare in adults. For example, in one of two groups studied, females that failed to give birth were also more prone to be marked as very underweight by the farmers. High levels of weight loss during the winter also correlate with high levels of stereotypy, and LQ H[WUHPLV, may even indicate effective starvation. Low body reserves can also cause, as well as reveal poor welfare: small females may be more prone to severe weight loss when nursing, and low body weights increase the risk of over-winter mortality. However, caution needs to be applied when using weight changes to assess mink welfare. They can be affected by many factors not necessarily related to stress, such as activity levels, feed levels, reproductive state, ambient temperature, and in the case of nursing females, the size of their litters. Thus for example, mink lose c. 10% of their bodyweight over-winter even if fed DG OLELWXP. When comparing experimental groups, these factors therefore need to be standardised before data collection, or controlled for statistically during analyses. E 3HOW TXDOLW\ In a range of species, coat condition is often affected by chronic stress, via the metabolic effects of glucocorticoids and the suppressing effect chronic stress often has on grooming. Minks’ pelt qualities may also reflect the level of allo-grooming
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