Medicinal plants and their effective compounds can develop the useful microbial populations (e.g. lactic acid bacteria) and inhibit pathogenic and non beneficial microbes' colonization in the gastrointestinal tract, increase the length of villi and improve the performance of broiler chickens [1]. The advantages of medicinal plants utilization in poultry diets include their simple usage, the absence of adverse side effects likelihood on animal performance, and leaving no harmful residues in their products. Harmala with the scientific name of Peganum harmala is a perennial and non fluff plant from the family of Nitrariaceae. Seeds from this plant are rich in carbohydrates, lipids, proteins, minerals, alkaloids and amino acids. Alkaloids are the active compounds of harmala which also known as Beta-Carbolines, and accumulate in parts of the seeds and roots of the plant. They include Harman, Norharman, Harmine, Harmalol, Harmaline, Vasyzin and Vasyzinun. Dried harmala seeds contain 35% protein, 17% oil and Harmaline, Harmine, Harman, Harmalol, Peganin, Isopeganin, Dipeganin, Vasizin and Vasyzinun alkaloids [2]. Alkaloids, Flavonoids and anthraquinones are the main phytochemical compounds of harmala. It has been reported that harmala extract decreased the body weight and increased the relative weight of liver in broilers [3]. In this study, 288 one-day old Ross 308 broiler chicks were randomly assigned to 4 treatments and 4 replication of 18 birds in each per treatment. The experimental treatments were control (with no feed additive), 0.02% Virginiamycin as growth promoter antibiotic, 0.25% harmala seed powder and 0.50% harmala seed powder. At the end of experimental period (42 day of age), two birds from each cage with the closest body weight to the cage mean weight were selected and slaughtered after recording their live body weights and their carcass, breast, thigh, liver, and abdominal fat weights were measured in proportion to live body weight. The data were analyzed
