الفهرس 
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Abstract
In this experiment, we used 240 one day old Cobb broiler chicks obtained from a commercial hatchery, fed a balanced commercial starter and grower ration (basal ration) and vaccinated against Newcastle, Gumboro according to the previously mentioned vaccination program. The chicks were divided into four groups and the treatments used were Group 1 (n=60): fed basal ration and water without drug treatment. Group 2 (n=60): treated with yeast beta-glucan at a concentration level of 25 µg/ml drinking water/day + basal ration Group 3 (n=60): treated with Sodium butyrate at a concentration level of 0.49 mg/ml drinking water/day + basal ration Group 4 (n=60): treated with Sodium butyrate at a concentration level of 0.98 mg/ml drinking water/day + basal ration The chicks were weighed individually at the beginning of the experiment then weighed weekly until the end of the experiment at 42 days old. Also the feed intake was weighted weekly at the same periods to evaluate the productive traits (Body weight, Body weight gain, feed conversion ratio, relative growth rate and organ index weight). At the end of experiment 10 birds of each group (3 treated groups and 1 control group) were slaughtered and blood samples were collected to estimate the hematological parameters (PCV%, Hb%, RBCs count and WBCs count). Serum samples from 10 birds of each group (3 treated groups and 1 control group) were separated to estimate the biochemical parameters (total protein, albumin, globulin, A/G ratio, ALT, AST, ALP, serum urea, creatinine, serum triglycerides, cholesterol, total bilirubin). Some internal organs (intestines, liver, kidney, spleen, bursa and stomach) from 5 birds of each group (the 3 treated groups and 1 control group) were collected to evaluate the histopathological alterations caused by drugs administration. Also, five birds of each group (the 3 treated groups and 1 control group) were weighted and slaughtered then dissected. Samples of breast muscle were collected and stored at -80 oC for molecular studies (monitoring the genotypic changes in the expression of the growth related gene, Insulin-like Growth Factor 1 Receptor (IGF1R), and the digestibility and food conversion ratio (FCR) related gene, Growth Hormone Secratoguge Receptor (GHSR The obtained results were as following a. Productive traits 1. The total body weights and body weight gains were improved in all treated groups of chicks in comparison with the control group The total relative growth rate of chicks treated with yeast beta-glucan was not improved in comparison with the control group. Chicks treated with sodium butyrate (0.49mg or 0.98 mg/ml. drinking water/day) showed improved relative growth rate in comparison with control group of chicks3. The total feed conversion ratio of chicks treated with sodium butyrate (0.98 mg/ml. drinking water/day) was improved in comparison with the other treated and control groups of chicks. There was statistically non-significant improvement in the FCR between chicks treated with yeast beta-glucan or chicks treated with sodium butyrate (0.49 mg/ml. drinking water/day) and control group4. The organ index weights of liver, heart, spleen, kidney, stomach and bursa showed no significant differences between all treated and control groups of chicks.
b. Blood picture1. The PCV% was increased in all treated groups of chicks in comparison with the control group. The Hb% of chicks treated with yeast beta-glucan and chicks treated with sodium butyrate (0.98 mg/ml. drinking water/day) were significantly increased in comparison with the chicks treated with sodium butyrate (0.49 mg/ml. drinking water/day) and control group. There was no difference between Hb% of chicks treated with yeast beta-glucan and chicks treated with sodium butyrate (0.98 mg/ml. drinking water/day). Also, there was no difference between Hb% of chicks treated with sodium butyrate (0.49 mg/ml. drinking water/day) and control group. The RBCs count was increased in all treated groups in comparison with the control group. The WBCs count of chicks treated with yeast beta-glucan was significantly increased in comparison with chicks treated with sodium butyrate (0.49 mg or 0.98 mg/ml. drinking water/day) and control group. The WBCs count of chicks treated with sodium butyrate (0.98 mg/ml. drinking water/day) was also significantly increased in comparison with chicks treated with sodium butyrate (0.49 mg/ml. drinking water/day) and control group. There was no difference between WBCs count of chicks treated with sodium butyrate (0.49 mg/ml. drinking water/day) and control group. Biochemical results. Serum total protein and albumin content of chicks treated with sodium butyrate (0.49 mg or 0.98 mg/ml. drinking water/day each alone) was increased in comparison with the control. While there were no differences in serum total proteins and albumin of chicks treated with yeast beta-glucan and control group. Also, there were no significant differences in serum total proteins and albumin of chicks treated with yeast beta-glucan and chicks treated with sodium butyrate (0.49 mg or 0.98 mg/ml. drinking water/day each alone. The globulin content was not differed between chicks treated with yeast beta-glucan and control chicks. Chicks treated with sodium butyrate (0.49 mg or 0.98 mg/ml. drinking water/day each alone) showed a siginificant increase in serum globulin content in comparison with control chicks. The A/G ratio were not differed between all the treated and control groups of chicks. The ALT and ALP levels were not differed between all the treated and control groups chicks. The AST level of chicks treated with sodium butyrate (0.98 mg/ml. drinking water/day) was increased in comparison with the other three groups of chicks. There were no significant differences between the AST levels of chicks treated with yeast beta-glucan, chicks treated with sodium butyrate (0.49 mg/ml. drinking water/day) and control group. Serum urea and creatinine levels were not differed between all the treated and control groups of chicks. Triglycerides levels of all the treated and control groups of chicks were not significantly different. The cholesterol levels of chicks treated with sodium butyrate (0.49 mg or 0.98 mg/ml. drinking water/day) were significantly increased in comparison with chicks treated with yeast beta-glucan and control group. There was no significant difference between chicks treated with sodium butyrate (0.49 mg/ml. drinking water/day) and chicks treated with sodium butyrate (0.98 mg/ml. drinking water/day) in cholesterol level. Also, there was no significant difference between chicks treated with yeast beta-glucan and control group in cholesterol levels. The total bilirubin levels of all treated groups of chicks were significantly decreased in comparison with control group. There were no significant differences between total bilirubin levels of all treated groups of chicks. Histopsthological findings: . Chicks treated with yeast beta-glucan showed a significant increase in intestinal villi length without a significant increase in intestinal villi width in comparison with control group. While, chicks treated with sodium butyrate (0.49 mg or 0.98mg/ml. drinking water/day each alone) showed a significant increase in intestinal villi length and a significant increase in intestinal villi width compared with control group. Liver of chicks treated with yeast beta-glucan or chicks treated with sodium butyrate (0.49 mg/ml. drinking water/day) showed a normal histological structure of the hepatic cords, hepatocytes and central vein in comparison with the control group. While, liver of chicks treated with sodium butyrate (0.98 mg/ml. drinking water/day) showed a normal histological structure of hepatocytes and congestion of central vein in comparison with the control group. Kidney of chicks treated with yeast beta-glucan showed a congestion of blood vessels. Moreover, kidney of chicks treated with sodium butyrate (0.49 mg or 0.98 mg/ml. drinking water/day each alone) showed a congestion of intertubular blood capillaries. Spleen of chicks treated with YBG (25 µg/ml. drinking water/day) showed a relatively normal red and white pulp in comparison with the control group. Moreover, spleen of chicks treated with sodium butyrate (0.49 mg or 0.98 mg/ml. drinking water/day) showed a hyperplasia of red pulp . Bursa of fabricious of chicks treated with sodium butyrate (0.49 mg or 0.98 mg/ml. drinking water/day) showed a normal histological structure with mild lymphoid depletion. While, bursa of fabricious of chicks treated with yeast beta-glucan showed a mild to moderate lymphoid depletion. Stomach of chicks treated with yeast beta-glucan and chicks treated with sodium butyrate (0.49 mg or 0.98 mg/ml. drinking water/day each alone) showed a normal histological structure in comparison with the control group at 42 days from drug administration. Molecular results1. mRNA expression of IGF1R was significantly increased in the treated groups of chicks (chicks treated with yeast beta-glucan and sodium butyrate (0.49 mg or 0.98 mg/ml. drinking water/day each alone)) in comparison with the control group. Among the three treated groups, chicks treated with yeast beta-glucan showed the highest expression level (about 4 fold more than the control group), while chicks treated with sodium butyrate (0.98 mg/ml. drinking water/day) showed a moderate increase in IGF1R gene expression (about 2.75 fold more than the control group). Chicks treated with sodium butyrate (0.49 mg/ml. drinking water/day) showed the lowest expression level (about 2.25 fold more than the control group). . mRNA expression of GHSR was significantly increased in the treated groups (chicks treated with yeast beta-glucan and sodium butyrate (0.49 mg or 0.98 mg/ml. drinking water/day each alone)) in comparison with the control group. Among the three treated groups of chicks, chicks treated with yeast beta-glucan showed the highest expression level (about 3.5 fold more than the control group), while chicks treated with sodium butyrate (0.98 mg/ml. drinking water/day) showed a moderate increase in GHSR gene expression (about 3 fold more than the control group). Chicks treated with sodium butyrate (0.49 mg/ml. drinking water/day) showed the lowest expression (about 2 fold more than the control group).