Utilization of Fermented Pistia Leaves in the Diet of Rohu, Labeo rohita (Hamilton): Effects on Growth, Digestibility and Whole Body Composition

The present study aimed at re-cycling of an aquatic weed (water lettuce, Pistia sp.) as a component in formulation of low cost non-conventional carp diet. Dried Pistia leaves (PL) was bio-processed through solid state fermentation (SSF) for 15 days at  32 ± 1 °C by a tannase producing yeast, Pichia kudriavzevii (GU939629) isolated from the gut of a freshwater carp, Cirrhinus cirrhosus. SSF of PL was effective in reducing the contents of crude fibre and antinutritional factors (e.g., tannin, phytic acid and trypsin inhibitor) significantly (P < 0.05), whereas enhancing crude protein, lipid, ash, total free amino acids and fatty acids. Six isonitrogenous (35%) and isocaloric (17 kJ g−1) experimental diets were prepared incorporating raw (R1–R3) and fermented (F1–F3) PL at 10, 20 and 30% levels by weight replacing fishmeal (FM) and other feed ingredients into a FM-based reference diet and fed to rohu, Labeo rohita fingerlings (initial weight 3.39 ± 0.06 g) for 80 days. In general, fish fed diets with SSF-processed PL resulted in significantly better growth, nutrient digestibility, carcass composition and digestive enzyme activity compared to the diets with raw PL. Fish fed the diet F2 containing 20% fermented PL had the highest live weight gain (106.3%), specific growth rate (SGR, % day−1), protein efficiency ratio and apparent net protein utilization. The highest protein gain (40.84%) and lipid accumulation in the carcass were also recorded in the fish reared on the diet F2. The present study might suggest incorporation of bio-processed PL up to 20% level (12.5% of FM replacement) without interfering growth, feed utilization efficiency and body composition in L. rohita fingerlings.