The present study was conducted to investigate the effects of synbiotic (SYN) containing Enterococcus faecium and Inulin on blood metabolites, nutrients apparent digestibility and performance of sheep fed alfalfa based diet. The 21 Farahani sheep averaging body weight 33.9 kg were allocated in a completely randomized design with 7 replicates in each treatment. The basal diet was formulated based on NRC (1989) and three treatments were; T1 = un-supplemented treatment (control), T2 = 2 g/d/h SYN supplemented, and T3 = 10 g/d/h SYN supplemented treatments. The synbiotic was supplemented once a day at the time of morning meal. The experiment lasted 12 weeks which the first week was for adaptation period. Supplementation of SYN had no effect on dry matter intake (DMI), daily gain (DG) and feed conversion rate (FCR). Digestibility of DM, OM, and CP were not affected with SYN supplementation. However, digestibility of NDF improved significantly in supplemented treatments (NDF digestibility was 46.09, 47.11 and 49.54% for treatments 1, 2 and 3, respectively) (P < 0.05). Considering the blood metabolites, both non-esterifies fatty acids (NEFA) and total immunoglobulin (total IG) were affected with supplementation (blood total IG concentration was 1.91, 1.95 and 2.27 mg/dl for treatments 1, 2 and 3, respectively) (P < 0.05). The blood urea nitrogen (BUN), glucose and albumin concentrations did not differ among treatments. Based on the present study it can be concluded that although SYN supplementation had no effect on performance traits of sheep, it had significant effect on both fiber digestibility and immunoglobulin concentration in blood.

Key words: Synbiotic, sheep, digestibility, blood metabolites.