Embryonic Development and Nutritional Modulation through In Ovo Feeding in Broiler Chickens

This review evaluates current knowledge on <i>in ovo</i> feeding (IOF) as a nutritional strategy to improve embryonic development and post-hatch performance in broiler chickens. Modern broiler chickens exhibit rapid growth and substantial early metabolic demand, making the embryonic period a critical phase in which nutrient availability strongly influences physiological maturation. Concurrently, eggs from older breeder hens often display altered yolk composition, reduced albumen quality, and weakened antioxidant status, collectively imposing nutritional and metabolic constraints on the developing embryos. IOF has emerged as a promising approach to alleviate these limitations by delivering nutrients, amino acids, vitamins, probiotics, or other bioactive compounds directly into specific embryonic compartments during late incubation. Evidence from numerous studies indicates that IOF promotes gastrointestinal maturation, enhances immune function, supports metabolic transitions, and improves early growth performance. Administration of amino acids, particularly arginine, tryptophan, and threonine, further contributes to gut health, muscle development, and antioxidant capacity. Despite these demonstrated benefits, variation in injection timing, dosage, and absorption dynamics underscores the need for standardized protocols and deeper mechanistic understanding. Overall, this review provides an updated synthesis of current findings and outlines practical considerations for the effective application of IOF as a nutritional strategy to enhance embryonic development, improve chick quality, and alleviate breeder-age-related constraints in modern broiler production.