Rearing catfish Heteropneutes fossilis on feed supplemented by fermented leaf meal of Ipomoea aquatica

Replacement of fish meal by cost effective and sustainable plant resources in the formulation of feed for fish is a viable option to alleviate the current crisis in fish feed industries arising due to high cost and non-availability of fish meal. The present research was aimed to evaluate if fermented leaf meal of the aquatic plant Ipomoea aquatica could be used as a fish meal alternative in the formulation of feed for the catfish Heteropneustes fossilis .  Fresh green leaves of I. aquatica were sun dried and finely ground to make Ipomea leaf meal (ILM), which was then fermented for 12 days by the phytase producing bacteria Stenotrophomonas maltophilia strain KUAKSP1 (GenBank Accession No. KY790423) isolated from rumen of goat. Four iso-proteinous, iso-lipidous and iso-energetic feeds were formulated by replacing 0, 25, 50 and 75% of fish meal by the fermented Ipomoea leaf meal (FILM). Protein digestibility of the feeds was evaluated within 12 days in an indoor experiment in glass aquaria and growth performance of the fish was evaluated after 8 weeks rearing in outdoor cement tanks. H. fossilis grew better on FILM supplemented feed as compared to fish meal based control feed. Maximum apparent protein digestibility (APD) of the feed, maximum weight gain (WG) and specific growth rate (SGR) and minimum FCR of the fish were found in 50% replacement group. However, crude protein (CP) and crude lipid (CL) deposition in the muscle of the fish and activity of protease in the gut was higher in 25% replacement group. It is concluded that H. fossilis accepts and grows well on the plant based FILM supplemented feed. For better growth management of the fish, incorporation of FILM in the feed should be restricted to 25 to 50% of fish meal.