Mohammad Hossien khanjani

Aquaculture is rapidly expanding as a source of protein production. One of the challenges facing aquaculture is the supply of feed, and the highest cost in aquaculture is related to this sector, which accounts for about 40 to 60 percent of the costs. Today, aquaculture costs can be reduced by using by-products (animal and plant) in aquatic animal diets. The use of by-products in fish diets is a common, economical and sustainable method in modern aquaculture. By-products used in fish diets are divided into two main categories: animal (fish powder, meat and bone powder, blood powder, feather powder, poultry offal powder) and vegetable (including meal, rapeseed meal, soybean, sunflower, cottonseed). Also, by-products of milling wheat and other grains, which are a source of energy and fiber, and the by-product of the ethanol production industry from grains, which is a source of protein and energy, can be used as a by-product in fish diets. The use of by-products in fish diets leads to improved specific growth rate, protein intake, protein efficiency ratio, gross feed conversion efficiency, better feed efficiency, improved survival rate and increased weight of farmed fish. According to studies, replacing corn flour with cowpea hull powder at a level of 50% to 100% increased the growth performance of C. gariepinus fry. The present study addresses the importance of by-products in fish diets and achieving sustainable aquaculture.