Efficacy of Duckweed-Spirodela for Low Cost Carp Feed Formulation

Feeding experiments were conducted to assess the efficacy of dried duckweed(Spirodela) in carp feed. Spirodela was cultured in plastic pools using cow dung and poultry dropping as manure, which were harvested periodically and sun dried to make Spirodela powder. Experimental diets were prepared by incorporatingSpirodela powder @ 20% in all the diets excluding control diet, D-I (de-oiled rice bran -40%, de-oiled mustard cake -40% and meat cum bone meal-20%). Diet D-II and D-III were prepared by replacing 50% of de-oiled rice bran and 50% of de-oiled mustard cake respectively with Spirodela powder. However, Diet D-IV was prepared by replacing 100% of meat cum bone meal with Spirodela powder. These diets were fed to Indian major carps carps (Labeo rohita and Cirrhinus mrigala) under semi-intensive rearing system for 180 days. Fingerlings ofL. rohita fed diet D-III recorded significantly higher gain in weight than those fed diets D-I (Control), D-II and D-IV. Whereas, in case ofC. mrigala, highest weight gain was recorded for the group fed diet D-IV which however, did not differ significantly from those fed diet D-III, but was significantly higher than both control (D-I) and D-II fed groups. Overall results revealed better feed conversion ratio (FCR) and protein efficiency ratio (PER) in fish diet D-III (FCR=0.82, PER= 4.6) followed by D-IV (FCR=0.90, PER=4.1), D-I (FCR=0.97, PER=3.7) and D-II (FCR=1.05, PER=3.1). 16.83 and 12.77% higher yield was recorded in fish fed D-III and D-IV diets compared to those fed control diet D-I. Inclusion of dried Spirodela @ 20% in carp feed by replacing 50% of mustard cake or 100% of meat cum bone meal not only resulted in positive growth response in both the species but also lowered the feed cost by 15.94% and 49.25%, respectively and hence holds great potential for utilization in carp feed.