Prepared by Assistant Lecturer Redha Abbas Hameed Department of Animal Production Techniques Poultry nutrition is considered the fundamental pillar of the livestock production industry. With the increasing global restrictions on the use of antibiotics as growth promoters due to the emergence of antibiotic-resistant bacterial strains, scientific research has shifted toward probiotics as a safe and sustainable alternative. This article aims to review the role of beneficial microorganisms in improving feed conversion efficiency and supporting the bird’s immune system. 1. Concept of Probiotics in Animal Production Probiotics are live microorganisms (bacteria or yeasts) added to the diet in controlled amounts to enhance microbial balance in the intestine. Among the most common strains used in the poultry sector are lactic acid bacteria (Lactobacillus) and yeasts (Saccharomyces cerevisiae). 2. Mechanisms of Action in the Digestive Tract These additives work through several technical pathways: • Competitive Exclusion: Beneficial bacteria occupy attachment sites on the intestinal wall, preventing pathogenic microorganisms such as Salmonella and E. coli from colonization. • Improved Digestion: These microorganisms secrete enzymes that help break down fibers and complex proteins, thereby increasing nutrient absorption efficiency. • Immune Stimulation: They activate gut-associated lymphoid tissues, leading to higher levels of antibodies in the bird’s bloodstream. 3. Performance Indicators The addition of probiotics leads to: • Improved Feed Conversion Ratio (FCR): Reducing the amount of feed required to produce one kilogram of meat. • Increased Live Body Weight: Accelerating daily growth rates, particularly during the early weeks of life. • Reduced Mortality Rate: By minimizing digestive disturbances caused by bacterial contamination. Based on technical evidence, we recommend: • Selecting probiotic strains that can withstand feed pelleting temperatures. • Starting supplementation from day one of age to ensure the establishment of a healthy intestinal microbial environment. Al-Mustaqbal University… the leading private university in Iraq.