Efficacy of ascorbic acid and different sources of orange peel on growth performance, gene expression, anti-oxidant status and microbial activity of growing rabbits under hot conditions

Orange peel and its extract are good sources of phenols and vitamin C that can be used as powerful antioxidants and antibacterial. The effects of dietary ascorbic acid (AA), orange peel powder (OPP) and orange peel extract (OPE) supplementations on growth performance, blood biochemicals, gene expression and antioxidant status of growing rabbits under hot conditions were investigated. A total of 80 weaned Giant Flander male rabbits, five weeks old (606.25 +/- 10.08 g), were randomly assigned to four groups. The first group received untreated diet (control group). The other groups received diets supplemented with 0.5 g AA/kg diet, 2% OPP and 500 mg OPE/kg diet. The lowest feed conversion ratio (FCR) was recorded by rabbits consumed diet supplemented with AA. Supplementations of OPP and OPE reduced blood plasma total cholesterol, low density lipoprotein and very-low density lipoprotein concentrations. The tested diets reduced triglycerides, total lipids, hydrogen peroxide, malondialdehyde levels, Staphylococcus aureus and Escherichia coli of the rabbits cecum. Supplementation of OPE improved activities of superoxide dismutase gene (6.1475) and insulin-like growth factor-1 (9.2108). Conclusively, dietary supplementation of OPE improved rabbit performance through improving antioxidant enzyme activities as well as upregulation of insulin-like growth gene. Additionally, OPP and OPE (2% and 500 mg/kg diet, respectively) had antibacterial effects for growing rabbits under hot conditions.