Differences in novelty behaviour for pigs with different coping styles

Studies in various species have shown that an animal could react either proactively or reactively to a challenging situation. The backtest has been used in pigs to classify them as either proactive or reactive animals. In this test a piglet of about two weeks of age is put on its back and manually restrained. During one minute, the number of escape attempts is counted along with other measures such as for instance the number of vocalizations. Piglets that struggle much are considered to be high resisters (HR) or the more proactive animals and piglets that hardly struggle are considered to be low resisters (LR) or the more reactive animals. Many studies have been done to investigate whether pigs with different coping styles (i.e. HR or LR pigs) differ in behaviour, physiology and immunology. Until now, the results are inconclusive. We performed a study with 480 pigs that were tested in a backtest at one and a half week of age and subsequently tested at 7 weeks of age in a groupwise 10 min human approach test (HAT) and at 13 weeks in an individual 10 min novel environment test (NET), where after 5 min a bucket was dropped from the ceiling. During the HAT, HR pigs tended to spent more time near the person than LR pigs. During the first 5 min of the NET, we found hardly any differences between HR and LR pigs, but after the drop of the bucket, HR pigs were more vocal, more active, and tended to touch the bucket sooner than LR pigs. In contrast, LR pigs stood more alert than HR pigs. These results show that pigs with different coping styles indeed react differently in response to a challenging situation.