This paper discusses the ethical implications of applying the concept of behavioural needs to captive animals. This is done on the basis of analysing the scientific literature on farmed mink and their possible need for swimming. In the wild, American mink (Mustela vison) are semi-aquatic predators, lending initial support to the claim that captive mink with no access to adequate swimming facilities experience a thwarted behavioural need. Scientific studies show a disparate picture. Consumer-demand experiments, where the animals have been conditioned to work for environmental resources, consistently show that mink place high value on swimming water, whereas other studies indicate the opposite, which has led scientists to question whether this preference constitutes a genuine behavioural need. In this paper, we take a methodological turn and discuss whether the oft-used concept of behavioural needs provides the best possible account of what is indispensable to an animal. Seen from a more complex understanding of behavioural needs, we suggest that lack of swimming opportunities for farmed mink constitutes a welfare problem. Further, it is argued that the decision of which paradigm to use in research on animal needs has not only ethical consequences, but is in itself a value-based choice.

The welfare of sows kept in two different group housing systems, namely voluntary cubicle pens housing small static groups and a split-yard housing system housing a large dynamic group, were examined. Each week, four newly weaned sows were introduced into either a voluntary cubicle pen or the split-yard system, with a total of eight groups of four sows introduced into each system. Behavioural and skin lesion data were recorded during the sows’ first 5 weeks in either system. Agonistic behaviours were performed more frequently during week 1 than in subsequent weeks in both housing systems (P < 0001). Sows in the voluntary cubicle pens spent more time standing inactive (P < 0001) and spent less time in exploratory (P < 005) and locomotory (P < 001) behaviours. However, sows in the split-yard system had higher skin lesion scores (P < 001) and engaged in more social (P < 005) and agonistic interactions (P < 005). These agonistic interactions included attacks (P < 005) and fleeing (P < 0001) throughout the 5-week observation period and fighting (P < 0001) during week 1 only. The split-yard system, therefore, appeared to offer sows a more stimulating social and physical environment than the voluntary cubicle pens, but also led to higher levels of aggression and skin damage. Both housing systems, therefore, appear to compromise sow welfare in different ways.

Welfare-related physiological and behavioural responses were studied in farmbred blue foxes (Alopex lagopus). Comparisons in space quantity were made between two different-sized shed cages (50 cm long (W50) and 120 cm long (W120); each 105 cm wide ✕ 70 cm high) and for one out-of-shed pen (5 m long ✕ 3 m wide ✕ 1·8 m high; W500). Each option had a wire-mesh floor. Furthermore, we tested how floor material affects responses by comparing the W500 foxes in wire-mesh floor pens with foxes housed in earthen floor pens (E500: 5 m long ✕ 3 m wide ✕ 1·8 m high). Each test group comprised 20 juvenile males maintained in pairs. The experiments lasted from weaning in July to pelting in December. Final body weights of the W500 foxes were significantly lower than those of the W50 or W120 foxes. Claw length of back foot was longer for E500 than for W500 foxes. Posture of front feet was the most folded for W50 and the least folded for E500 foxes. Breaking strength of tibia was highest for foxes housed on the earthen floor (E500). Gastrocnemius muscle succinate dehydrogenase activity tended to decrease and the number of leucocytes tended to increase with cage size. Alanine-aminotransferase and aspartate-amino transferase activities were significantly higher in foxes housed in shed cages (W50, W120) than in enclosures (W500, E500). Creatine-kinase activity tended to decline with increasing cage size. Highest and lowest open field activity was found for E500 and W50 foxes in both wire-mesh and earthen floor test arenas. Some differences were found in body weight-related organ sizes between groups. Heart weight was significantly higher in W500 than in W50 or W120 foxes. Brain weight was significantly lower in W50 than in W500 foxes. Liver weight increased with increasing cage size. Capture time was significantly lower for W50 and W120 foxes than for W500 or E500 foxes. Cortisol levels after capture were significantly higher in foxes from enclosures (W500, E500) than in those from shed cages (W50, W120), but after ACTH stimulation the levels were similar in each group. Rectal temperatures after restraint were highest in foxes from W500. Fur properties of W500 and E500 foxes were poorer than those of W50 or W120 foxes.

The welfare of early-weaned pigs in different housing systems was examined using a range of indicators. Three replicates of 20 pigs were weaned at 6·4 kg live weight into either: (a) deep-straw; (b) Straw-Flow®; (c) large flatdeck; (d) small flatdeck. A kenneled lying area was provided in (a) and (b). The floor in (c) and (d) was expanded metal. Stocking densities were 0·23 m2 per pig in (a), (b) and (c) and 0·17 m2 per pig in (d). After 4 to 5 weeks (19·6 kg live weight), 16 pigs from each pen were moved into Straw-Flow grower pens (0·68 m2 per pig) and observed until slaughter at 90·6 kg. The remaining pigs were grouped together to examine the effects of mixing. At weaning, 24·1% of pigs had foot injuries. Pigs with foot injuries recovered quickly on deep-straw but the injuries increased in flatdecks immediately after weaning (Straw-Flow was intermediate). Injuries were more persistent in the small flatdeck. Deep-straw prevented adventitious bursitis of the hock. After 1 month in the grower pens, there was no residual treatment effect. Antibody response was examined by immune challenge with keyhole limpet haemocyanin (KLH). Immunoglobulin (Ig) response was greater in straw pens. Pigs mixed at 20 kg showed a decreased immune response to KLH challenge. Growth and food intake showed no treatment effects; food conversion ratio was poorer in (c) than in (b) or (d).

Choice tests are an effective means of assessing the short-term environmental preferences of captive animals. The preferences shown by eight thoroughbred horses (Equus caballus) for three commonly used bedding materials (paper, straw and shavings) were investigated. For each preference test two choices were presented in separate boxes joined by an unbedded corridor. Time spent in each compartment and associated behaviours were recorded. Despite a positional bias, horses clearly showed a preference for straw bedding (42·9 (s.e. 3·6) %) over shavings (35·2 (s.e. 3·4) %, P < 0·05), straw (42·0 (s.e. 37) %) over paper (29·3 (s.e. 3·4) %, P < 0·05) and shavings (41·6 (s.e. 4·3) %) over paper (27·7 (s.e. 3·7) %, P < 0·001) based on percentage of observed time spent on the substrate. Straw bedding increased the occurrence of bedding related activities, with more of these activities in choices where straw was available (P < 0·001) and in these choices the activities being preferentially expressed in the straw alternative (P < 0·001). Straw may therefore be preferred as it allows the expression of a wider number of motivationally significant activities.