| Summary: | The following studies were designed to gain a better understanding of individuality, social stress and behavioural development in domestic pigs. The first study used a series of behavioural observations and tests to assess the individuality of, and effect of regrouping stress on, 89 pigs. The studied factors were "approachability", "exploration," and "aggression". Regrouped pigs took longer to approach a novel object and human during a novel arena test (NAT) (P=0.01). The second study used the NAT to classify 222 pigs, as either slow (83 180 s), medium (32-79 s) or fast (0-27 s) to approach a human. Pigs were sorted into groups of all slow pigs (uniform slow), all fast pigs (uniform fast) or slow, medium and fast pig (diverse). Intact litters served as the control. Pigs in intact litters took less time to approach in the NAT (9.3 versus 28.6 ± 3.03 s; P=0.02), fought less (0.45 versus> 3.61 ± 0.45 fights/pig/hour; P<0.01) and tended to grow faster (863 versus 805 ± 21.6 g/day; P=0.09) than pigs in regrouped treatments. Slow approaching pigs became faster to approach over time (P<0.05) and fast pigs slowed down (P<0.05). The third study investigated the effect of positive human contact on reactions to novelty and regrouping stress. Half of the 228 pigs received frequent positive human contact. The pigs were assessed in the NAT, and classified as either fast or slow to approach a novel object. The pigs were regrouped based on time to approach (creating uniform or diverse groups) and whether they had received human contact (conditioned or unconditioned). Pigs that were in conditioned, uniformly slow to approach groups had longer fight durations (217.8 versus <119.6 ± 34.3 s/pig; P<0.05) than the other regrouping treatments. The NAT is a useful tool for determining behavioural differences among pigs. Regrouping affected the habituation response to the NAT. There are differences in patterns of habituation for slow, medium or fast approaching pigs. Behavioural conditioning appears to affect the response of slow approaching pigs to regrouping.
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