Dietary selenium-enriched olive leaves supplementation in fattening rabbits: 2. In vivo and meat oxidative status

Recent studies have shown the positive effects of selenium in animal and human nutrition for its role as essential component of glutathione peroxidase enzyme. The incorporation of olive leaves added with Se in feeds could be a suitable strategy to increases the antioxidant content of diet aiming to improve the health and oxidative status of animals. The aim of this study was to assess the influence of dietary supplementation of 10% olive leaves, treated or not with Se, on the oxidative status of plasma and rabbit meat. Thirty New Zealand White weaned rabbits of 30 days of age were divided in 3 groups (10 animals/group) and subjected to different dietary treatments: control feed (C) provided ad libitum; control feed þ10% olive leaves (OL) and control feed þ10% olive leaves treated with 2.17 mg/kg of Se (SE). At 75 days of age rabbits were slaughtered and blood samples were taken from carotid vein. After carcass refrigeration for 24 h at 4 C, longissimus lumborum muscle was removed. The antioxidant content (tocotrienols, tocopherols, lutein, zeaxanthin and carotene) was carried out on olive leaves, and experimental diets. The oxidative status of plasma and meat (TBARS, carbonyls and vitamins) was also determined. Data were analyzed with a linear model with the fixed effect of dietary treatment. No differences were found on the antioxidant content and lipid oxidative status of plasma; however, the groups fed olive leaves showed a higher protein oxidation (p<.01) respect to control (2.98 and 2.69 vs 0.35 nmol/mg protein in SE, OL and control, respectively). In the meat the carbonyls were also higher with olive leaves enrichment, conversely the lipid oxidation was lower in such groups probably due to the balance of antioxidant defense. Indeed, the a-tocotrienol content was lower (p<.05) in the OL and SE meat respect to the control (25.70 and 38.99 vs 63.08 ng/g, respectively). On the other hand, the a-tocopherol content was higher (p<.05) in SE meat samples (892.34 vs 650.46 and 570.35 ng/g in SE, control and OL, respectively), probably for an indirect protective effect operated by selenium. In conclusion, the present study suggests that the dietary Se enrichment, improved the oxidative status of rabbits, whereas remain unclear its metabolic route. Further studies are needed to understand whether the higher protein oxidation is directly related to the olive leaves addition and to find which compounds are responsible of such effect.