Abstract
A single manipulable enrichment is often introduced to the pens of farmed American mink (Neogale vison) to combat stereotypic behaviour and behaviours or temperaments associated with poor welfare (e.g. inactivity, fear, and aggression). This enrichment is provided early in life, but it is unclear the age at which enrichment is most effective at preventing stereotypic behaviour and ameliorating welfare. Here, a group of enriched kits (EK) were provided with multiple enrichments that were periodically exchanged to renew novelty from 4-15 weeks of age, earlier than typical enrichment provision on farms, after which they were housed with a single standard enrichment into adulthood. The effects of EK enrichment on kit behaviours and long-term stereotypic behaviour were compared to that of two groups reared with a single standard enrichment (standard housed; SH and enriched at whelping; EW). Inactivity in the nest-box was decreased in EK kits as juveniles relative to other groups, however, social play was reduced and lying awake was increased compared to EW and SH juveniles, respectively. Stereotypic behaviour in the kits as adults was not prevented by EK interventions; in fact, EK kits may have developed more diverse sub-types of stereotypic behaviour than EW and SH kits. Moreover, kit temperament did not appear to be affected. EK enrichment may have been ineffective in improving welfare due to the timing of its removal or potential frustration induced by its removal. Recommendations are provided for future research regarding critical periods of enrichment to improve welfare in species such as farmed mink.