الفهرس 
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Abstract
In recent years, there has been an increase in the use of organic acids (OAs) as growth promoters because of the fear of antibiotic resistance and the implications for human health. The OAs plays an important role in gut health in animals. An important objective of dietary OA is the inhibition of intestinal bacteria competing with the host for available nutrients. Organic acids have more or less pronounced antimicrobial effects in countering pathogenic bacteria, depending on both the concentration of the acid and the bacterial species that is exposed to the acid. Organic acids and their salts have been used in poultry feed for decades because they have a positive response in growth performance. In general, chicks fed on the basal diet supplemented with OA at different levels had significantly (P < 0.05) greater live body weights and increased weight gain across all experimental periods compared to the control group. No significant difference was found in any of the measured carcass traits. The digestion coefficients of CP, EE, CF, NFE, and ME significantly (P < 0.05) improved in all treated OA groups compared to the control. Organic acids supplementation had increased digestive enzyme activities (amylase and lipase). All OAs treated groups had higher (P < 0.05 or 0.01) albumin and globulin concentrations than the control group. The IgG, IgM and IgA levels were significantly greater in the OA groups than the control group. The activities of SOD and TAC, GSH and CAT as well as digestive enzymes were improved due to OAs augmentation compared to control. Plasma levels of MDA were decreased (p˂.0001) in the chicks fed OAs. Chicks fed OA at different levels had significantly decreased caecal content of TBC, coliform, E. coli and Salmonella. The use of OAs improved egg number, egg mass and FCR when compared to control at all ages. Chicks breeders fed OAs-treated diets consumed less food than the other diets during the overall period. Augmentation of OAs to laying chick diets improved fertility percentage. Addition of OAs to laying chick diets reduced the shell percentage and shell thickness, but increased the Haugh unit. The use of OAs in chick breeder’s diets tended to decline TC, TG, LDL, and VLDL in plasma. Inclusion of OAs in the diets of chick breeder improved the immune parameters. The activity of SOD and TAC was higher in OA groups than the control. In conclusion, supplemental OAs could improve the performance, digestive enzymes, immunity and antioxidant indices, mitigate intestinal pathogens, productive and reproductive performance in growing and laying chicks.