Do pigs find a familiar odourant attractive in novel surroundings?

Sixty-four DurocxLandrace pigs (Sus scrofa) of both sexes were reared from birth to 6 weeks of age in either fresh air or an atmosphere containing an artificial odourant (Ambi-Pur). Their behavioural responses to a novel environment (a modified open field) were then observed over 1h when the test arena contained either the familiar Ambi-Pur odourant or ammonia gas at 45ppm. Although members of other mammalian and avian species are attracted to familiar odours in otherwise novel surroundings, the presence of Ambi-Pur had no effect on the pigs' readiness to enter the novel arena from a sheltered area or on other fear-related behaviours following entry (p>0.05). Pigs kept in fresh air from weaning until test were generally less active and spent less time at the centre of the open field if the test was carried out in an ammoniated atmosphere rather than fresh air; this suggests that they found ammonia aversive. On the other hand, the presence of ammonia at test accelerated approach to the centre of the open field and increased the number of entries into that area and the percentage of time spent there as well as overall activity in pigs that had also been exposed chronically to this gas at 43ppm from weaning until testing at 6 weeks (p<0.05). Thus, after chronic exposure to either ammonia gas or an artificial odourant, ammonia was the only stimulus that appeared to act as an attractive agent for pigs placed in an otherwise novel environment.