Partial Replacement of Fish Meal with an Aquatic Macrophyte, Ceratophyllum demersum in the Diet of Common Carp, Cyprinus carpio var. communis Fingerlings

A 12-week feeding trial was conducted to investigate the nutrient utilization, growth performance, and hematological indices of Cyprinus carpio var. communis fingerlings fed diets based on aquatic macrophyte, Ceratophyllum demersum as a replacement of fish meal (FM). Six isonitrogenous and isocaloric diets containing graded levels of C. demersum 0%, 5%, 10%, 15%, 20%, and 25%, respectively, as replacer of FM were formulated. Total of 360 fingerlings with an initial weight of 3.65 +/- 0.98 g were randomly stocked in 70 L plastic tanks water volume 60 L connected with a continuous flow-through system (1-1.5 L/min) for each treatment and were run in triplicate having 20 fish in each tank. At the end of the feeding trial, it was observed that the C. carpio var. communis fingerlings receiving 5% and 10% C. demersum in the diet showed improvements in live weight gain (LWG), specific growth rate (SGR), feed conversion ratio (FCR), and protein efficiency rate (PER). While further addition of C. demersum as a replacement of FM from 15% to 25% led to the progressive decline in the values of LWG, SGR, FCR, and PER. Hematological data also exhibited a linear declining trend beyond the 10% C. demersum replacement level. The fish fed with higher inclusions of C. demersum in each diet significantly (P<0.05) affected whole body composition with the lowest protein and fat amounts recorded at higher replacement levels significantly (P<0.05). The highest protein and fat contents were observed at 5% and 10% diets. Except serum glucose, cholesterol, alanine aminotransferase (ALT), and aspartate aminotransferase (AST), the other serum indices exhibited a decreasing trend with increasing inclusion of C. demersum in the diet. The results of the present study clearly demonstrated that the inclusion of 10% C. demersum did not affect the growth and other parameters of C. carpio var. communis fingerlings compared to the 50% FM diet. However, it is recommended that 10% FM can be substituted without compromising the growth and nutritional quality of fish.