Performance of rabbits and oxidative stability of muscle tissues as affected by dietary supplementation with oregano essential oil

The effect of dietary supplementation with oregano essential oil on the performance of rabbits, and the susceptibility of the produced raw and thermally treated muscle tissue to lipid oxidation during refrigerated storage, were investigated. A total of 96 weaned rabbits were separated into four equal groups with three subgroups each. One group was given the basal diet and served as control, two groups were administered diets supplemented with oregano essential oil at levels of 100 and 200 mg/kg diet, whereas the remaining group was given a diet supplemented with alpha-tocopheryl acetate at 200 mg/kg. During the 42-day experimental period, body weight and feed intake were recorded weekly and the feed conversion ratio was calculated. Feeding the experimental diets to rabbits, performance parameters were not affected. Therefore, dietary oregano essential oil exerted no growth-promoting effect on rabbits. With increased supplementation of oregano essential oil, malondialdehyde values decreased in both raw and thermally treated muscles during refrigerated storage. This finding suggests that dietary oregano essential oil exerted a significant antioxidant effect. Dietary supplementation of oregano essential oil at the level of 200 mg/kg was more effective in delaying lipid oxidation compared with the level of 100 mg/kg, but inferior to dietary supplementation of 200 mg alpha-tocopheryl acetate per kg. This study indirectly provides evidence that antioxidant compounds occurring in oregano essential oil were absorbed by the rabbit and increased the antioxidative capacity of tissues.