Brewers’s spent grains as an economical alternative to fishmeal in goldfish (Carassius auratus) diet

Cost-effective and nutritionally balanced diet is fundamental for successful ornamental fish farming. This study aimed to investigate replacement level of fishmeal with brewer’s spent grain (BSG) in the diet of Carassius auratus to reduce production cost. A control diet was formulated to contain ۴۰% crude protein and ۲۱ kJ g⁻¹ of gross energy. Three experimental diets were formulated by replacing ۱۰%, ۲۰%, and ۳۰% of fishmeal in the control diet with BSG. Using a completely randomized design, ۱۲۰ fish (۱.۱۳±۰.۰۶ g) were assigned to ۱۲ concrete-glass tanks (۷۰×۳۰×۳۰ cm) at the rate of ten per aquarium, representing three tanks for each diet. The fish were fed twice a day (۰۸:۰۰ am and ۰۳:۰۰ pm) until satiation for six weeks. Water quality parameters were measured daily and maintained within the standard range. At the end of the experiment, fish survival was ۹۵%. Length and weight gains of fish fed the experimental diets were higher (p<۰.۰۵) than those fed the control diet. Polynomial regression curves delineated the maximum length gain at ۱۸.۵% replacement of fishmeal with BSG while the maximum weight gain was at ۹.۶%. However, daily feed intake and feed conversion ratio did not differ (p>۰.۰۵) among the dietary groups. Condition factor of fish was significantly higher (p<۰.۰۵) in the treated groups. The estimated cost per kilogram feed showed a decreasing trend towards increasing level of BSG in the diet. In conclusion, ۱۸.۵% dietary BSG with the expense of fishmeal improved the growth of goldfish and reduced the feed cost. Further studies are recommended to investigate nutrient utilization and immunity of fish.

کلیدواژه ها:

Low-cost feed ، Calico Ryukin ، Ornamental fish ، SGR ، Low-cost feed ، Calico Ryukin ، Ornamental fish ، SGR