56 MARCH 2024 • WORLD AQUACULTURE • WWW.WAS.ORG nitrogen and CO2 to generate carbohydrates and ammonia, while producing oxygen during photosynthesis. Azolla can be substituted for nitrogenous fertilizers to increase crop yield and quality while lowering production costs. It lowers the rate of evaporation in irrigated rice fields and waterfowl, fish, shrimp, snails, crabs, ducks, chickens, pigs, cattle and buffalo can be raised on a diet of Azolla (Figure 1). Morphology Azolla is a free-floating, rapidly growing small aquatic fern. Azolla is also known as mosquito fern, duckweed fern and fairy moss. Among Azolla spp., Azolla pinnata (hereafter referred to as Azolla) is the most common species in the Indian subcontinent. Typical measurements for Azolla are about 1.5 to 3.0 cm in length and 1 to 2 cm in breadth, including stem, leaves and roots. The stem is often called the rhizome. The leaves enclose large mucilage filled cavities for hosting the Cyanophycean alga, Anabaena azollae. Azolla and Anabaena azollae maintain a symbiotic relationship, where the alga offers nitrogen to the Azolla, and the Azolla is used as a habitat for the alga. This property of nitrogen fixation has made Azolla capable of fixing atmospheric nitrogen in water in the form of ammonium ion (NH4 +), becoming available as soluble nitrogen for aquatic plants. Aquaculture is a fast growing industry that provides high quality animal protein. However, sustainability in aquaculture development with high marginal profit depends on affordable feed availability. Nutritious aquafeeds impact the health and growth of cultured fish species. Protein ingredients used in aquafeeds should meet several important criteria such as excellent amino acid, high digestibility, good palatability, and absence of non-nutritional factors. Fishmeal has been a primary source of protein used in aquafeeds due to the presence of essential amino acids (EAAs), minerals, vitamins (choline, biotin, and vitamin B12), A, D, and E, and omega (n−3) fatty acids (Refaey et al. 2023). However, reliance on fishmeal as protein source creates cascading effects on wild fish populations. Moreover, the rising cost of fishmeal is one of the main obstacles in the expansion of aquaculture. In general feed cost constitutes 5060 percent of operational cost in aquaculture and protein sources constitute the major share of the feed cost. In the search for alternatives to high cost and non-renewable fishmeal, aquafeed formulations have been shifting to plant-based proteins such as soybean meal, wheat gluten meal and cottonseed meal. Aquatic weeds are traditionally considered waste, but some, like azolla, can be incorporated as ingredients in fish diets. Azolla can be grown at a low cost under a controlled environment on a farm site during a short period of time. It can fix ambient Azolla in AquaFeeds for Profitability and Sustainability of Aquaculture Vivekanand Bharti, Kamal Sarma, Tarkeshwar Kumar, S. K. Ahirwal and Jaspreet Singh Aquaculture is a fast growing industry that provides high quality animal protein. However, sustainability in aquaculture development with high marginal profit depends on affordable feed availability. Nutritious aquafeeds impact the health and growth of cultured fish species. Protein ingredients used in aquafeeds should meet several important criteria such as excellent amino acid, high digestibility, good palatability, and absence of non-nutritional factors. Fishmeal has been a primary source of protein used in aquafeeds due to the presence of essential amino acids (EAAs), minerals, vitamins (choline, biotin, and vitamin B12), A, D, and E, and omega (n-3) fatty acids. FIGURE 1. Utilising Azolla in agriculture, livestock and fisheries FIGURE 2. Steps of Azolla culture in FRP tank
RkJQdWJsaXNoZXIy MjExNDY=