The role of novelty in environmental enrichment for the weaned pig

Abstract

Habituation to environmental enrichment objects can occur rapidly. Novelty of an object is an important property involved in initiating and maintaining exploration, and this can be achieved by renewing objects. The aims of this study were to assess whether alternation of two contrasting objects increased enrichment value, and whether simultaneous access increased overall object-directed behaviour in comparison with single presentation of each object. The experiment was designed as a 2 × 2 factorial, with 2 enrichment objects (suspended rope and loose wood block) and 2 presentation methods (continuous access, or weekly alternation). An additional treatment examined object use when both objects were presented simultaneously. Five replicate pens, each of 10 weaned pigs, were allocated to each treatment: R, continuous rope; W, continuous wood; R/W, alternation rope-wood; W/R, alternation wood-rope; R + W, simultaneous rope and wood. Observations of behaviour were made for two 1-h periods, three times a week for a 4-week period. Direct scan samples at 5-min intervals measured use of the enrichment object(s), penmate and pen manipulation, and general activity. These were supplemented by two 24 h time-lapse video recordings made in the first and last experimental weeks. Object interaction was significantly affected by treatment, with W spending a lower overall proportion of observations in contact with the object than the other treatments (in order 0.102, 0.037, 0.093, 0.110, 0.134, s.e.d. 0.007; P < 0.001). In R, week had a significant effect on rope interaction, which decreased in week 2 and increased again in week 3 when new rope was added, although rope interaction was still lower in week 3 than in week 1 (0.106 vs. 0.151, respectively, s.e.d. 0.017; P < 0.01). When R/W and W/R received rope for a second time, rope interaction was lower than in the first presentation week (R/W, 0.166 vs. 0.129, s.e.d. 0.017; P < 0.05). Interaction with wood was always lower than with rope (in R + W, 0.03 vs. 0.19, respectively, s.e.d. 0.027; P < 0.001). Object interaction was additive in R + W when compared to R and W. To conclude, the rotation of enrichment objects did increase novelty, although habituation still occurred. Rope was extremely effective at occupying the pigs’ time, with interaction levels comparable to those previously reported for straw.