Effects of early and later life environmental enrichment and personality on attention bias in pigs (Sus scrofa domesticus)

Abstract

We investigated effects of early and later life housing on attention bias, as an indicator of affective state, in pigs differing in coping style [reactive (LR) vs. proactive (HR)]. Pigs (n = 128) in barren or enriched housing from birth (B1 vs. E1) that experienced either a switch in housing at 7 weeks of age or not (creating B1B2, B1E2, E1E2, and E1B2 treatments), were studied in a 180-s attention bias test at 11 weeks. Pigs exposed to a 10-s-auditory-and-sudden-motion threat in the test arena paid more attention to the location of the threat, were more vigilant, showed less eating, more walking and were more likely to utter high-pitched vocalisations than non-threat pigs. During threat presence, HR pigs from post-switch enriched housing (E2-HR, i.e., B1E2 + E1E2) showed more vigilance but less exploration than others. After threat removal, no effects were found on time spent paying attention to the threat, vigilance, and eating, but E2-HR pigs paid attention to the threat more frequently, were more likely to utter high-pitched vocalisations and walked more compared to (part of) other groups, suggesting the most negative affective state in these animals. E2 pigs grunted more than B2 pigs. Thus, current housing, but not early life housing, affected behaviour in a personality-dependent manner in this attention bias test. Housing effects were opposite to expectation, possibly due to the short-term effect of the relative contrast between the home pens of the pigs and the test room. This potentially overruled putative long-term effects of environmental conditions on attention bias.

Effects of Early and Current Environmental Enrichment on Behavior and Growth in Pigs

“…Rather, the successive negative contrast test suggested a "protective" effect of early life enrichment irrespective of the current environment, as pigs reared in enriched pens were less susceptible to reward loss (46). In the attention bias test, no early life effects were found, whereas the impact of current housing was opposite to expectations, which might be due to the test circumstances (42), and found only for pigs with a proactive coping style. Thus, further research is needed to evaluate whether a change from enriched to barren housing conditions and vice versa not only affects pigs' behavior, but also their affective state in the long run.…”

“…On the other hand, reactive pigs may be more influenced by their long-term housing environment. Several studies reported that reactive pigs were more affected by the absence or presence of enrichment than proactive pigs (37,40,41), although we recently found that the behavior of proactive pigs in an attention bias test was more influenced by enrichment (42). Thus, the impact of enrichment and a loss or gain of enrichment may depend on the personality characteristics of the pig under study, which may therefore be relevant to take into account.…”

“…Distribution of (early and later life) barren and enriched pens over the rooms was balanced. Part of the pigs within a pen were exposed to tests for emotional state and immunity, the results of which are published elsewhere (42,46,47). This was balanced for the treatments.…”

“…However, other studies do not support this suggestion. We subjected part of the pigs to an attention bias test (42) and successive negative contrast test (46) to assess a potential long-term impact of their housing (history) on affective state, but failed to show the expected effects of the negative or positive housing switch on the responses of pigs in these tests. Rather, the successive negative contrast test suggested a "protective" effect of early life enrichment irrespective of the current environment, as pigs reared in enriched pens were less susceptible to reward loss (46).…”

Investigating Personality in Polar Bears Using the Concept of Behavioral Instability

“…These different personalities are expressed by consistent behavioral responses under various conditions, that can vary with different variables e.g. population density, stress and enrichment [2,3,4]. The personality of an animal can influence its welfare, as these responses can vary between individuals, i.e.…”