0
Resilience, the capacity of animals to be minimally affected by a disturbance or to rapidly bounce back to the state before the challenge, may be improved by enrichment, but negatively impacted by a high allostatic load from stressful management procedures in pigs.
Methods: We investigated the combined effects of diverging environmental conditions from weaning and repeated mixing to create high allostatic load on resilience of pigs. Pigs were either exposed to barren housing conditions from weaning onwards or provided with sawdust, extra toys, regular access to a “play arena” and daily positive human contact. Half of the pigs were exposed to repeated mixing and the other half to one mixing only at weaning (minimal mixing). To assess their resilience, the response to and recovery from a lipopolysaccharide sickness challenge and a Frustration challenge were studied. In addition, potential long-term resilience indicators, i.e. natural antibodies, hair cortisol and growth were measured.
Results: Some indications of more favorable responses to the challenges in positive human contact pigs were found, such as lower serum reactive oxygen metabolite concentrations and a smaller area under the curve of serum reactive oxygen metabolite after lipopolysaccharide injection. In the Frustration challenge, positive human contact pigs showed less standing alert, escape behaviors and other negative behaviors, a tendency for a smaller area under the curve of salivary cortisol and a lower plasma cortisol level at 1 h after the challenge. Aggression did not decrease over mixings in repeated mixing pigs and was higher in barren housing conditions pigs than in positive human contact pigs. Repeated mixing did not seem to reduce resilience. Contrary to expectations, repeated mixing pigs showed a higher relative growth than minimal mixing pigs during the experiment, especially in the week of the challenges. Barren repeated mixing pigs showed a lower plasma cortisol concentration than barren minimal mixing pigs after the lipopolysaccharide challenge, which may suggest that those repeated mixing pigs responded less detrimentally than minimal mixing pigs. Enriched repeated mixing pigs showed a higher level of IgM antibodies binding keyhole limpet hemocyanin than enriched minimal mixing and barren repeated mixing pigs, and repeated mixing pigs showed a sharper decline in IgG antibodies binding Bovine Serum Albumin over time than minimal mixing pigs. Hair cortisol concentrations were not affected by enrichment or mixing.
Conclusion: Enrichment did not enhance the speed of recovery from challenges in pigs, although there were indications of reduced stress. Repeated as opposed to single mixing did not seem to aggravate the negative effects of barren housing on resilience and for some parameters even seemed to reduce the negative effects of barren housing.
Luo L, van der Zande LE, van Marwijk MA, Knol EF, Rodenburg TB, Bolhuis JE, Parois SP. Impact of Enrichment and Repeated Mixing on Resilience in Pigs. Frontiers in Veterinary Science. 2022; 9. https://www.frontiersin.org/articles/10.3389/fvets.2022.829060