Effect of the Iberian pig rearing system on blood plasma antioxidant status and oxidative stress biomarkers

Forty-four pure Iberian pigs (14 months age, similar to 96.5 kg live weight) were randomly assigned to four different rearing systems: i. Free range conditions along with an acorn and pasture feed (AGFR), ii. Free range conditions with grass availability and fed on concentrate (CGFR), iii. Intensive system fed on concentrate supplemented with 100 ppm of alpha-tocopheryl acetate (alpha-TAc) (CI) and iv. Intensive system fed on concentrate supplemented with 200 ppm of alpha-TAc (CEI). Blood samples were taken every 30 days during 90 days (t0: 0d, t1: 30d, t2: 60d and t3: 90d -slaughter-) and tocopherols isomers contents, 2,2'-azino-bis (3-ethylbezothiazoline-6-sulfonic acid) (ABTS), 2,2-diphenyl-1-picrylhydrazyl (DPPH) and ferric reducing antioxidant power (FRAP) activities were measured in plasma as determinants of antioxidant status. At slaughter time (t3), TBA-RS and protein carbonyls were measured as biomarkers of lipid and protein oxidative damage. Acorn, grass and concentrate feeds were analysed and classified according to the content of tocopherols and antioxidant potential. 200 ppm of alpha-TAC supplementation increased alpha-tocopherol contents in feed. Acorns and pasture had high gamma- and alpha-tocopherol contents, respectively, and both were found to show the highest antioxidant activities. Plasma from AGFR pigs contained significant (P < 0.05) higher amounts of alpha-tocopherol than those from CI and CGFR pigs and the highest amounts of gamma-tocopherol (P < 0.05). At t1 and t2, DPPH and FRAP activities were significantly (P < 0.05) higher in AGFR plasma than in CI and CEI plasma. At slaughter time plasma from AGFR pigs had a higher resistance to oxidation with significant (P < 0.05) higher ABTS, DPPH and FRAP activities than plasmas from pigs kept in confinement and fed on concentrates. Lipid oxidation was significantly lower (P < 0.001) in plasma from AGFR pigs than in CI pigs while protein oxidation was not significantly affected (P > 0.05). Plasma from pigs fed on 200 ppm alpha-TAC enriched diets (CEI) or grass (CGFR) had intermediate antioxidant activities and TBA-RS. These results indicate that free range rearing system increased blood plasma antioxidant status while reduced lipid oxidative biomarker.