الفهرس 
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Abstract
The present experimental study was carried out at the research station of Poultry Production Department, Faculty of Agriculture, Alexandria University between months of March to April, 2019. The purpose of the study was to investigate the potential effects of melittin, Thepax or their combinations instead of traditional antimicrobial and antiviral treatments on broiler performance and other important biomarkers for broiler development such as immunological and physiological status as well as breast meat chemical composition. Finally, economic indices were also calculated. The first tested substances used in the experiment was melittin which derived from honeybee venom and has multiple biological properties, whereas the second one was Thepax it is the patent new commercial inactivated yeast (Saccharomyces cerevisiae) which obtained from the brewery industry. The experiment was conducted on 810 unsexed one day- old broilers chicks (Ross 308) which were purchased from a commercial hatchery. Chicks were randomly allocated in 9 experimental groups with equal average body weight for 5 weeks of experimental period, and each group had 90 broilers arranged in 3 replicates of 30 broilers each. Then, birds were raised on floored pens with a deep litter system of wood shaving in an open-sided house under natural conditions and general management practices. Feed and water were provided ad libitum and the indoor temperature was maintained at 33o C for the first 3 d, after that temperature was gradually reduced by 3o C per week until reaching 24o C; this temperature was maintained until the end of the experiment. During the first week, 22 h of light was provided with a reduction to 20 h afterward. Moreover, the distribution of experimental pens was arranged to avoid any effect of the location in the bird’s house. Broilers of the experimental groups were fed on corn-soya bean meal basal diet that was formulated to meet Ross nutrient requirements for starter and grower finisher growth periods. Depended on the tested additive programs and access of veterinary care, the experimental treatments were labeled as follows: T1: Traditional antimicrobial and antiviral treatments without any of studied additives (control). T2: Melittin (83.3 µg /L water) supplementation without therapy treatments. T3: Melittin (166.6 µg /L water) supplementation without therapy treatments. T4: Thepax (0.25 g/kg diet) supplementation without therapy treatments. T5: Thepax (0.50 g /kg diet) supplementation without therapy treatments. T6: Melittin (83.3 µg /L water) and Thepax (0.25 g/kg diet) supplementation without therapy treatments. T7: Melittin (166.6 µg /L water) and Thepax (0.25 g/kg diet) supplementation without therapy treatments. T8: Melittin (83.3 µg /L water) and Thepax (0.50 g /kg diet) supplementation without therapy treatments. T9: Melittin (166.6 µg /L water) and Thepax (0.50 g /kg diet) supplementation without therapy treatments. Data were collected in terms of productive performance, slaughter yields, some blood traits and histological structure of intestine. Finally, feed cost index and relative economic efficiency were calculated. The interesting results can be summarized as follows.