This chapter examines the incorporation of algae in animal feed, focusing on its nutritional composition and the impact of its nutrients on productive efficiency and animal health in livestock and aquaculture. Essential macronutrients such as proteins, lipids, and carbohydrates are analyzed, along with polyunsaturated fatty acids (docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA)), amino acids, vitamins, and bioactive antioxidants. The study evaluates the effects of these components on growth, digestibility, feed conversion, gut health, and immunity in various aquatic and terrestrial species. Practical applications are also explored, including dietary formulations that replace conventional ingredients with algae and bioencapsulation techniques to optimize nutrient absorption. On an economic level, the production costs of algae biomass and scalability challenges are examined, as well as regulatory barriers and the financial feasibility of implementing algae in animal production systems. Finally, the study considers algae’s potential to reduce the carbon footprint and contribute to sustainable production systems, supporting the transition to a bioeconomy in animal feed.