Steffen W. Hansen

Generalization of fear in farm mink, Mustela vison, genetically selected for behaviour towards humans

Abstract Mink offspring from two genetic lines, selected over 10 generations for confident (C) or fearful (F) reaction towards humans, were exposed to six different tests. The aim was to investigate whether this behavioural selection in mink has affected their reaction in other potentially fear-eliciting situations. A total of 192 naive mink, males and females, were tested over 6 weeks. C-mink had a shorter latency to get near and establish exploratory contact with a human than F-mink. F-mink maintained 6–10 times the distance to a human than C-mink. Similarly, C-mink had a markedly shorter latency than F-mink to approach and make contact with a novel object. C-mink also manipulated the object sooner and more often. In encounters with unfamiliar mink, C-mink were quicker to approach and establish nonaggressive contact than F-mink. C-mink had a shorter latency than F-mink to enter tubes within an X maze, and were more likely to visit these tubes. In contrast, F-mink made the most visits to other parts of the maze; number of visits may not, however, reflect just exploration. When presented with novel food, F-mink changed their behaviour more often than C-mink, indicating a higher degree of behavioural conflict. C-mink were also less hesitant than F-mink to approach and eat the novel food. In conclusion, offspring from a confident breeding line reacted with more exploratory behaviour than offspring from a fearful breeding line. Mink lines selected for behaviour towards humans thus generalized their fear responses across several social and nonsocial situations. Copyright 2002 The Association for the Study of Animal Behaviour. Published by Elsevier Science Ltd. All rights reserved.

Selection for behavioural traits in farm mink

Abstract Over a period of 6 years, more than 3000 farm mink were tested for their behavioural response to human contact. Using a simple test (the stick test) five times per generation, the mink were characterized and classified with regard to their response to human contact. Behavioural response that might be caused by genetic factors was found to occur in three lines selected for explorative, fearful, and aggressive temperament. Over six generations, a considerable quantitative difference in behavioural response between the three selection lines developed. Selection for fearful behaviour caused the normal habituation towards man to disappear, and 90% of the mink selected for fearfulness responded consistently with fear to human contact. A less distinct effect was found in mink selected for explorative behaviour at human contact. A possible explanation may be that the basic level of explorative behaviour in the population was relatively high, but also that the test used did not allow for a graduation of the explorative behaviour towards confidence. Apart from the last two generations of mink selected for fear, all lines have shown a pronounced difference in temperament between sexes showing that females were more fearful than males.

The development of on-farm welfare assessment protocols for foxes and mink: the WelFur project

The WelFur project aims at the development of on-farm welfare assessment protocols for farmed foxes (the blue fox [Vulpes lagopus], the silver fox [Vulpes vulpes]) and mink (Neovison vison). The WelFur protocols are based on Welfare Quality® (WQ) principles and criteria. Here, we describe the WelFur protocols after two years of developmental work. Reviews for each of the 12 WQ welfare criteria were written for foxes and mink to identify the welfare measures that have been used in scientific studies. The reviews formed the basis for potential measures to be included in the WelFur protocols. All measures were evaluated for their validity, reliability and feasibility. At present, we have identified 15 fox and 9 mink animal-based (or outcome-based) welfare measures, and 11 and 13 input-based (resource-based or management-based) measures. For both foxes and mink, each of the four WQ principles is judged by at least one criterion, and seven out of the 12 criteria include animal-based measures. The protocols will be piloted in 2012. Using the WQ project and protocols as a model has been a fruitful approach in developing the WelFur protocols. The effects of the WelFur protocols will provide benchmarks from which the welfare of animals on European fur farms can be assessed.

The Effect of Cage Environment and Ad Libitum Feeding on the Circadian Rhythm, Behaviour and Feed Intake of Farm Mink

The effect of cage size and nest box environment on circadian rhythm and on stereotyped and non-stereotyped activities was measured for 66 farmed female mink fed ad libitum. The behaviour of the an...

The Application of a Temperament Test to On-Farm Selection of Mink

The welfare of production animals can be improved by adapting the production system to the needs of the animals and/or by selecting those animals best adapted to the production system. As no documented improvements of mink welfare resulting from altered housing are readily available, a temperament test (the stick test) is now being applied for use under commercial farm conditions. The test, categorising the mink as fearful, exploratory or aggressive when a stick is inserted into the cage, has been developed and used for selection under experimental conditions. It has been demonstrated that the temperaments categorised in the stick test are related to reactions in novel object and intruder tests as well as to cortisone response to handling. In order to facilitate the use of the stick test in practice, it has been simplified and implemented on six Danish mink farms. On average, 60% of adult mink females were characterised as exploratory in August, but the percentage differed between farms. After 30 minutes of training, the farmers were able to perform the stick test with 74–100% agreement in results with an experienced tester. In order to improve welfare at farm level, a selection line of 200 exploratory females is established on each farm for the mating season in March 2000. During the first three years of selection, the effects of the behavioural selection on other welfare indicators, such as health, behaviour and production, will be monitored.

DEVELOPMENT AND POSSIBLE CAUSES OF FUR DAMAGE IN FARM MINK : SIGNIFICANCE OF SOCIAL ENVIRONMENT

The aim of the present experiment was to investigate the temporal development of fur damage in mink as well as the significance of social conditions (alone, in pairs or in family groups) on frequency and development of fur damage in mink kits. The adult generation was selected and distributed into two groups, partly on the basis of the frequency and character of the fur damage. The kits examined were offspring from these adult mink plus those from a randomly selected control group. Fur damage occurred when the kits were 2 months old irrespective of weaning time and social condition. Fur damage in the neck, however, only appeared when the animals were placed two or more together, so it can be deduced that the appearance of neck damage is not self‐inflicted. It may appear as a result of normal behaviour of mink in connection with mating and aggressive interactions and also as an abnormal behaviour probably caused by understimulation. Fur damage on the tail increased when mink were separated or when females ...

Benefits of a Ball and Chain: Simple Environmental Enrichments Improve Welfare and Reproductive Success in Farmed American Mink (Neovison vison)

Can simple enrichments enhance caged mink welfare? Pilot data from 756 sub-adults spanning three colour-types (strains) identified potentially practical enrichments, and suggested beneficial effects on temperament and fur-chewing. Our main experiment started with 2032 Black mink on three farms: from each of 508 families, one juvenile male-female pair was enriched (E) with two balls and a hanging plastic chain or length of hose, while a second pair was left as a non-enriched (NE) control. At 8 months, more than half the subjects were killed for pelts, and 302 new females were recruited (half enriched: ‘late E’). Several signs of improved welfare or productivity emerged. Access to enrichment increased play in juveniles. E mink were calmer (less aggressive in temperament tests; quieter when handled; less fearful, if male), and less likely to fur-chew, although other stereotypic behaviours were not reduced. On one farm, E females had lower cortisol (inferred from faecal metabolites). E males tended to copulate for longer. E females also weaned more offspring: about 10% more juveniles per E female, primarily caused by reduced rates of barrenness (‘late E’ females also giving birth to bigger litters on one farm), effects that our data cautiously suggest were partly mediated by reduced inactivity and changes in temperament. Pelt quality seemed unaffected, but E animals had cleaner cages. In a subsidiary side-study using 368 mink of a second colour-type (‘Demis’), similar temperament effects emerged, and while E did not reduce fur-chewing or improve reproductive success in this colour-type, E animals were judged to have better pelts. Overall, simple enrichments were thus beneficial. These findings should encourage welfare improvements on fur farms (which house 60-70 million mink p.a.) and in breeding centres where endangered mustelids (e.g. black-footed ferrets) often reproduce poorly. They should also stimulate future research into more effective practical enrichments.

Stress Physiological Status and Fur Properties in Farm Mink Placed in Pairs or Singly

Abstract The effects of keeping farm mink in pairs or singly from weaning to pelting on haematological, clinical-chemical and stress physiological variables, on body and organ weight, and on fur properties were examined in 96 mink kits in order to assess the consequences on welfare and productivity. Mink kept in pairs had better pelt quality than mink kept singly. No significant difference was found in frequency of hair chewing between mink in pairs and single mink. Bite marks on the leatherside of the pelt occurred only in mink kept in pairs. No significant difference was found between the groups in body weight, and organ weight corrected for body weight. Based on the physiological variables applied, no differences in welfare were shown between mink in pairs and single mink. Sexual differences were found for the enzymes ASAT and ALAT, for number of leucocytes, and for adrenal glands relative to body weight.

The effects of feed restriction on physical activity, body weight, physiology, haematology and immunology in female mink.

The aim of the present study was to investigate if adult mink females characterised as having a high or low residual feed intake (RFI) differed in their response to feed restriction with regard to activity, body weight loss and physiological parameters. For RFI-High, the activity was higher prior to the expected feeding time both in the cases of restrictive and ad libitum feeding indicating a changed RFI-High feeding motivation and a higher risk of developing stereotypic activity. The body weight gain and the feed consumption were higher for RFI-High than for RFI-Low when feeding ad libitum indicating that RFI-High has a higher growth potential and/or a higher energy requirement than RFI-Low. Signs of immunosuppression were shown in connection with restrictive feeding compared to ad libitum feeding, and RFI-High females seemed to be more susceptible to immunosuppression than RFI-Low females. Based on the present results, mink characterised as RFI-Low would be preferable as breeders because they involve lower feed costs and seem to be less susceptible to immunosuppression. They also seem to have less risk of developing stereotypic activity, which is beneficial for the welfare.

Effects of interrupted social contact on the social behaviour of calves and piglets

The use of traditional operant conditioning techniques to assess the behavioural needs of farm animals has been criticised because presenting short rewards repeatedly may interrupt bouts of behaviour and thereby devalue the reward. The two reported experiments (one including 12 calves and one including 12 piglets) aimed to investigate if interruption of social contact affects social behaviour. In both experiments, animals were housed in pairs (one test animal and one companion animal) in large pens with solid sides. The experiment included three periods: a pre-test period, a test period and a post-test period. Animals were separated for 24 h and then reunited for 24 h in each period. In the test period, the first 42 min of contact after reunification comprised 12 successive 3.5 min long periods separated by gaps, whereas in the pre- and post-test periods, the contact was continuous. Calves sniffed and licked each other more when social contact was interrupted (P<0.01), but no effects of interrupting social contact were found for social or locomotor play. In piglets, the test animals performed more flank pushing of the companion (P<0.01), and avoided the companion more (P<0.05), when social contact was interrupted, while no effects of interruption were found for parallel pressing, bites and head knocks, sniffing or locomotor play. The results suggest that if social contact is interrupted in an operant conditioning set up, some elements of aggressive behaviour may be stimulated in piglets.