Abstract
Enriched environments are known to beneficially affect the behavior of pigs, as compared with barren pens. The influence of enrichment may, however, depend on pigs' early life housing experiences. The aim of this study was to investigate the long-term effects of early and later life environmental enrichment on behavior and growth in pigs with different coping styles. Pigs were housed in either barren pens or in larger pens enriched with rooting substrates from birth, and half of them experienced a housing switch, i.e., a loss or gain of enrichment, at 7 weeks of age, creating four treatment groups. Home pen behavior and body weight were recorded until 19 weeks of age. Pigs were classified as reactive or proactive based on a backtest at 2 weeks of age. Enrichment increased time spent exploring, chewing, and play and decreased oral manipulation of penmates and pen-directed exploring and chewing. Behavior of pigs that switched from barren to enriched pens or vice versa reflected not only their actual environment, but also their early life housing. As early and later life enrichment affected most behaviors in opposite directions, effects of enrichment, or lack thereof, after the switch were more pronounced in pigs that had experienced a different early life condition. For instance, pigs experiencing an upgrade from barren to enriched pens seemed to “catch-up” by showing more exploration and play. Conversely, pigs exposed to a downgrade displayed more oral manipulation of penmates than ones kept barren throughout, which particularly held for pigs with a reactive coping style. Effects of early life and current housing on several other behaviors depended on coping style too. Pigs housed in enriched conditions appeared better able to cope with weaning than barren housed pigs, as they gained more weight and had higher feed intake post-weaning. Barren housed pigs had a lower body weight than enriched pigs just before the switch, after which growth was mainly determined by actual housing, with enriched kept pigs having a higher feed intake and body weight. Thus, not only current housing conditions, but also a (mis)match with the early life environment may affect behavior and growth of pigs.
Highlights
Pigs in intensive farming conditions are often housed in stimulus-poor, barren environments, which offer little potential to facilitate their natural species-specific behaviors
Several studies reported that reactive pigs were more affected by the absence or presence of enrichment than proactive pigs [37, 40, 41], we recently found that the behavior of proactive pigs in an attention bias test was more influenced by enrichment [42]
We found that the behavior of the pigs after the switch reflected their actual environment but was influenced by early life housing conditions
Summary
Pigs in intensive farming conditions are often housed in stimulus-poor, barren environments, which offer little potential to facilitate their natural species-specific behaviors. The limited living space, and the lack of materials for foraging and exploration in barren housing conditions, are major risk factors for the development of damaging oral behaviors, such as tail biting and ear biting [1,2,3]. These barren conditions can cause chronic stress in pigs, as reflected in physiological changes [4,5,6]. Some studies report enhanced growth rates in pigs kept in enriched environments [e.g., [12, 20, 21]], but see Camerlink et al [22] and Morrison et al [23], who did not find such an effect
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