Red seaweed, Gracilaria sp. a source of ingredients for the formulation of fish feed

Recent research on aquafeed has focused on using low-cost and nutrient-rich non-conventional feedstuffs. So, seaweeds can be considered a non-conventional feed ingredient for the aquafeed industry. This study evaluated the potentiality of selected seaweed (Gracilaria sp.) enriched feeds by assessing their effects on the growth performance, feed utilization, carcass composition, and palatability of Hypophthalmichthys molitrix. The study was conducted for 90 days under four treatments in 12 cages set in a pond at the Department of Fisheries, University of Rajshahi, Bangladesh. Four test feeds were made where one was without seaweed designed as SW0 (control) and three were enriched with seaweed (Gracilaria sp.) at the rates of 5, 10, and 15%, which were designed as SW1, SW2, and SW3, respectively. Sampling was conducted biweekly to evaluate weight increase. At the end of the study, the mean weight gain (MWG), specific growth rate (SGR), survival rate, and feed conversion ratio (FCR) were estimated using standard methods. In addition, carcass composition (protein, lipid, carbohydrate, moisture, and ash content) and palatability indicators (flavor, taste, and texture) of the fish were evaluated by following AOAC and organoleptic sensory methods. Significantly higher MWG and SGR were found in the fish of SW2, followed by the fish of SW1 and SW0, and lower in SW3, whereas the FCR was found better in the fish of SW2 compared to other treatments. The results of chemical analysis showed no significant difference in carcass composition but relatively higher carcass protein and lipid recorded in the fish of SW2. For the palatability test, a significantly higher organoleptic score was recorded in the fish of SW2 while lower in SW0. The outcomes of the study suggested that including 10% Gracilaria sp. can be effective in diets for H. molitrix with no negative results on the growth, carcass composition, and palatability indicators.