Effects of enrichment type, method of presentation and social status on enrichment use, behaviour and stress response of gestating sows
This study examined how enrichment type, different methods of presentation and social status of individual sows affect enrichment use, behaviour and stress in sows. Eight groups of 28 sows were studied, with additional data collected on six focal sows (3 dominant [Dom] and 3 subordinates [Sub]) per group. Four treatments were given in random order and lasted for 2 weeks. Treatments: 1) constant provision of wood on chains (Constant), 2) rotation (rope, straw, wood on chain: Rotate), 3) rotation with an associative stimulus (bell or whistle: Stimulus), and control (no objects). It was hypothesized that frequent rotation of enrichments would increase enrichment use and reduce habituation, and use of an associative stimulus would increase the initial response to new enrichments. Cameras were mounted over pens and time lapse photos taken at 10-minute intervals for an 8-hour period on days 1,8,10 and 12 to determine enrichment use and sows’ activity. Body weights of focal sows were recorded at beginning and end of study, aggression was evaluated using skin lesion scores on a scale of 0 (no injury) to 3 (severe injury). Saliva samples were collected and analyzed for cortisol level. Body weight and parity were compared between Dom and Sub sows using Proc Mixed. Enrichment use, and sows activity were compared across treatments using analysis of variance with repeated measures (Glimmix procedure SAS 9.4). Dom sows were of higher average parity and significantly heavier than Sub sows. Behavioural observations showed that a similar percentage of sows was present in the enriched area regardless of the enrichment treatment provided (P>0.05). Enriched sows were more active, spending a greater amount time standing than Control sows (P<0.05). There was tendency for greater percentage of sows contacting and near enrichments when materials were rotated and paired with a stimulus than constant (P=0.066). There were similar levels of enrichment use and no difference in lesions or cortisol levels between Dom and Sub sows. In live observations, a time of day by social status interaction was found, with Dom sows spending a greater amount of time standing and bar biting than Sub sows in the morning (P<0.05). Stage of gestation influenced saliva cortisol level, with an increase at 14 weeks of late gestation. In conclusion, the provision of enrichment objects increased sow activity with a greater percentage of enriched sows standing. No clear effect of habituation was found because the short treatment duration used in this study was not sufficient to observe sows’ response over time. Regularly changing the enrichments, especially with inclusion of straw on the floor tended to increase sows’ response to enrichment. Similar levels of enrichment use were observed among Dom and Sub sows. However, Dom sows were more active and showed more stereotypic bar biting compared to Sub sows. The results suggest that there was minimal competition in the group system studied as social status did not significantly affect enrichment use, aggression or stress levels.
sows, enrichment, welfare, social status, group housing
Master of Science (M.Sc.)
Animal and Poultry Science