Evaluation of the nutritional quality of four unexplored aquatic weeds from northeast India for the formulation of cost-effective fish feeds

A study was conducted to evaluate the nutritional potential of four commonly available, unexplored aquatic weeds namely, Salvinia cuculata, Trapa natans, Lemna minor and Ipomoea reptans from northeast India for ascertaining their suitability for utilization as supplementary fish feed with the aim to reduce the cost of commercial feeds. Results of proximate analysis showed that the crude protein content of the aquatic weeds ranged between 11.0% and 32.2% (w/w), whereas crude fibre and ash contents varied between 4.2% and 20% (w/w), and 13.3% and 31.2% (w/w), respectively. Protein to energy ratio (P/E) of these weeds ranged between 30.7 mg/kcal and 95.3 mg/kcal and the highest value was displayed by I. reptans. All these aquatic weeds contained high amounts of vitamins E and C and mineral elements required for the normal growth and development of fish.Analysis of antinutritional factors showed that the concentration (g%) of trypsin inhibitor (TIA) ranged from 1.1% to 1.5%, calcium oxalate concentration ranged from 0.6% to 3.5%, tannin concentration ranged from 0.25% to 0.93% and phytate concentration ranged from 0.004% to 0.005% in these plant samples, and the amounts of these antinutritional components were within the tolerable limits of fish, particularly for carp. The present study demonstrates that commercial exploitation of these aquatic weeds, particularly I. reptans and L. minor, for the formulation of cost-effective and balanced artificial fish feeds appears to be highly promising.