Abstract
ABSTRACT
The present study was designed to evaluate the effects of yeast beta-glucan (YBG) in comparison with sodium butyrate (SB) on the performance of broiler chickens, with special attention to their molecular, hematological, biochemical and histophathological effects. Therefore 240 one day-old Cobb broiler chicks were divided into 4 groups. The first group (n=60): chicks received basal ration and water without any treatment (and considered as a control group), the second group (n=60): chicks treated with 25µg YBG/ml. drinking water/day, the third group (n=60): chicks treated with 0.49 mg SB/ml. drinking water/day and the fourth group (n=60): chicks treated with 0.98 mg SB/ml. drinking water/day. The chicks received the treatment daily for 42 days. The obtained results showed that administration of YBG or SB showed a significant improved average weight gain (AWG) and feed conversion ratio (FCR). The growth promoting effects of these agents is a result of the improvement in the expression of Growth Hormone Secratoguge Receptor (GHSR) and Insulin-Like Growth Factor 1 Receptor (IGF1R). Both GHSR and IGF1R were significantly improved by 3.5 and 4 folds respectively in chicks treated with YBG(25 µg/ml. drinking water/day) , 2 and 2.25 folds respectively in group treated with SB (0.49 mg/ml. drinking water/day) and 3 and 2.75 folds respectively in group treated with SB (0.98 mg/ ml. drinking water/day). YBG and SB (0.49 mg or 0.98 mg/ ml. drinking water/day each alone) significantly increased packed cell volume (PCV)% and red blood corpuscles (RBCs) count in comparison with the control. YBG and SB (0.98 mg/ ml. drinking water/day) significantly increased hemoglobin concentration (HB)% and white blood corpuscles (WBCs) counts. Chicks treated with SB (0.49 mg or 0.98 mg/ ml. drinking water/day each alone) there was a significant increase in serum total protein, albumin and cholestrol in comparison with the control group. Moreover, in chicks treated with SB (0.98 mg/ ml. drinking water/day) AST was significantly increased in comparison with the control group. All treated groups showed significant reduction in total bilirubin level compared with control group. Other tested parameters in all treated groups were not significantly changed compared to control group. Intestines of all treated groups showed significant improvement in length and width of intestinal villi in comparison with the control group. From the obtained results, we can conclude that YBG and SB can be successively used as new alternatives of antibiotic growth promoting agents in broiler chicks.

Key words: Broiler, growth, sodium butyrate, beta-glucan, molecular studies