MASS PRODUCTION OF AQUATIC MACROPHYTE SPIRODELA POLYRHIZA, ITS AMINO ACID AND FATTY ACID PROFILES STUDY AND ITS USE IN CARPS’ FEED FORMULATION

Abstract

Aquaculture is one of the fastest growing food producing sectors in the world. It contributes immensely in food security, livelihood and employment generation. Fish and fishery products provide a healthy food for human consumption with high protein and low saturated fat. In commercial aquaculture, feed constitutes around 60-70% of total expenditure due to the use of fish meal and fish oil as a prime source of protein and lipid, respectively. The limited availability of fishmeal and its price are major concerns in the present scenario. Therefore, the rising price and shortage of diet components created a crucial call to find out an inexpensive, abundantly available and innovative alternative raw material to be used in place of fish meal for fish feed without compromising the growth and meat quality of fish. Freshwater duckweeds are a potential ingredient to replace the costly fishmeal in aquaculture. The present study aimed to evaluate the application of freshwater macrophytes as fish feed ingredient. In the present study twelve macrophytes were collected from different water bodies and were cultured in outdoor cemented tanks. Among twelve different cultured macrophytes, greater duckweed Spirodela polyrhiza was selected as a potential fish feed ingredient for its nutritional value. The culture technique of selected macrophyte S. polyrhiza was developed in outdoor cemented tanks using different manures. The organic manure was found suitable for the production of S. polyrhiza. The organic manure was used for the mass production of S. polyrhiza in ponds. The production rate of S. polyrhiza in ponds was 2020±150 tonnes/ha/year. Fish feeds were formulated by using Winfeed 2.8 software package (WinFeed UK Limited, Cambridge, United Kingdom). The incorporation of S. polyrhiza at various levels in the diets of Labeo rohita and Cyprinus carpio showed the beneficial effect on the fishes. It improved the digestive enzyme physiology of the fishes, thereby enhanced the growth rate. The biochemical composition study of fish showed that there was improvement in the compositions of fishes like, crude protein, crude lipid and amino acids contents. The omega-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) contents increased in S. polyrhiza supplemented diets fed common carp compared to other diets fed fish. Expression levels of delta-6-desaturase (fads2d6), elongation of very long chain fatty acids protein 2 (elovl2), elongation of very long-chain fatty acids protein 5 (elovl5) and fatty acid synthase (fas) were up-regulated in common carp fed greater duckweed based diets compared to others. The knowledge generated from the present study is useful in the formulation of cost-effected diets for carps and thereby, the production of nutrient rich fishes for consumers.