Joydev Maity and Bidhan C Patra
Keywords: Non-conventional fish feed, Azolla pinnata, Labeo rohita, antinutritional factor, pancreatic protease, RNA/DNA ratio
Abstract: Dried water fern (Azolla pinnata) leaf meal was substituted for fish meal in practical diets of Labeo rohita fingerlings. Five isonitrogenous diets (38% crude protein) were formulated in which fish meal (68.9% crude protein) was replaced at varying levels (D1 = Control, 0% replacement; D2 = 25%; D3 = 50%; D4 = 75% and D5 = 100%) with protein from Azolla meal (25.81% crude protein). Carp fed a control diet had significantly (p < 0.05) better growth response and nutrient utilization. Growth depression of fish increased with increasing dietary levels of Azolla meal. Diet D5 containing 100% replacement of Azolla meal gave the poorest feed conversion ratio as it contain higher amount of trypsin inhibitor. There was marked reduction in cost the diets incorporated with Azolla meal. With the gradual inclusion of Azolla meal in the diets, the pancreatic enzyme activity was increased significantly up to 50% replacement and then decreasing trend was noticed during 60 days feeding trial. Growth rate of Labeo rohita and RNA/DNA ratio were reduced by insufficiently heated meals but properly heated Azolla meal improve nutritional quality as well as improvement of growth rate. Dry processing methods other than sun drying are suggested for the improvement of nutritional quality of Azolla leaf meal in carp diets. It was concluded that the antinutritional or limiting factor present in Azolla leaf meal are antitryptic and reduces the growth rate, if do not take proper care for the nutritional security.
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