Departments of Animal Science, Shabestar branch, Islamic Azad University, Shabestar, Iran _____________________________________________________________________________ ABSTRACT The objective of this study was to investigate the effect of different level of virginiamycin (VIR) on Growth performance, biochemistry, and hematology blood parameters broiler chickens. A total of 240 day-old broilers (Ross 308) were randomly allocated to four groups of 15 chicks each. Each four groups assigned in completely randomized design with four replicate. Experimental groups consisted of: T1) Basal diet (control), and others groups T2, T3, and T4 with 10, 20, and 30 ppm VIR kg-1 diet respectively added to the basal diet. Body weights and, feed intake recorded as weekly and used for calculated FCR at 42 days. At the end of research four birds (one bird per replicate) selected and after sampling blood, slaughtered for determination organ weights. About 4 ml drawing blood sample from wing vein. Serum removed by centrifuge and stored in -20°C until analysis. The results indicated that supplemented diet with 20 ppm VIR kg-1 diet had significantly increased body weight (P<0.05), also had significantly decreased FCR compared with control and other groups (P<0.05). Relative weight of small intestine and abdominal fat had significantly decreased in T2 and T3 compared with control (P<0.05). Value of Ca, P, and Mg in serum had a trend increasing parallel with increased level of virginiamycin in diet (P>0.05). Concentrations of Triglyceride, and cholesterol showed decreasing trend among treatment compared with control group, but had not significant effect (P>0.05). In addition, the results current research showed that: 1) to add virginiamycin in diet was improved performance traits and important blood parameters, and 2) the best level of VIR to applied nutrition was 20 ppm kg-1 diets.
