Up-regulation of IGF-1 in the frontal cortex of piglets exposed to an environmentally enriched arena

Environmental enrichment (EE) is widely used in the life sciences to study effects of environment on the brain. In pigs, despite lack of EE being a key welfare issue there is little understanding of brain effects of EE in pigs. This project aimed to study the effects of exposure to an EE arena on piglet behaviours and on brain gene expression levels with a focus on IGF-1 and related genes. Eight litters of large white × landrace × Hampshire piglets were farrowed and raised in a free farrowing system (PigSAFE). At 42 days of age, 6 piglets per litter were given access to an enriched arena with plentiful peat, straw and space, (in groups of 4 made up of stable pairs) for 15 min per day on 5 consecutive days to allow them to habituate to the apparatus. Piglet behaviours were recorded in the arena for 15 min periods on 3 consecutive days. On the final day only one pair of test piglets per litter was given access to the arena. Brain tissue was collected within 45 min of the test from piglets exposed to the arena on the day and their non-exposed littermate controls. RNA was extracted from the frontal cortex and QRT-PCR for selected genes run on a Stratgene MX3005P. In both the home pen and the EE arena litters spent the largest proportion of time engaging in foraging behaviour which was significantly increased in the enriched arena (t(7) = 5.35, df = 6, p = 0.001). There were decreases in non-running play (t(7) = 4.82, p = 0.002) and inactivity (t(7) = 4.6, p = 0.002) in the arena. A significant fold change increase (FC = 1.07, t = 4.42, p = 0.002) was observed in IGF-1 gene expression in the frontal cortex of piglets exposed to the enriched arena compared to those not exposed on the day of culling. No change in expression was observed in CSF1, the IGF-1 receptor gene nor in any of the binding proteins tested (IGFBP1-6). There was a weak tendency for increased expression of the neurotrophic factor BDNF1 (fold change: 1.03; t(7) = 1.54, p = 0.1). We believe this work is the first to explore effects of EE on pig brain physiology and development, and also points to a potential role for IGF-1 in brain effects of EE.