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ABSTRACTThis study was carried out to evaluate the effects of dietary concentrate: forage (C: F) ratio on fat deposition, fatty acid composition, oxidative stability and mRNA expression levels of sirtuins genes associated with adipose tissue metabolism of subcutaneous fat in Black Tibetan sheep. Three diets with different C: F (HC: 70:30, IC:50:50 and LC: 30:70) were fed to fifteen weaned male lambs (2-month-old, 10.05 ± 0.96 Kg). The experiment lasted for 120 d. Five lambs from each group were randomly selected and slaughtered at the end of the experiment. The subcutaneous fat thicknesses increased with increasing concentrate level (P < 0.05). The concentration of polyunsaturated fatty acid (PUFA), C15:1 and C18:2n decreased by feeding the HC diet (P < 0.05). Both glutathione peroxidase (GSH-Px) and superoxide dismutase (SOD) activities significantly increased as dietary concentration levels decreased (P < 0.05). Additionally, SIRT1and SIRT2expression level was downregulated (P < 0.05) with increasing concentration supplementation (P < 0.05and P < 0.05, respectively). In conclusion, the addition of 70% concentration supplementation is not recommended in Black Tibetan sheep, considering that no benefits were observed for nutrient utilization, oxidative stability or economic returns, while the supplementation of C: F at 50:50 proved to be suitable for finishing lambs.