Evaluation of graded replacement levels of fish meal with duckweed (Lemna minor) in diets of Channa striata fingerlings: Growth performance, nutrient utilization, and economic analysis

Abstract

A 90-day feeding trial was conducted to evaluate the effects of graded replacement of fish meal with L. minor (0%, 25%, 50%, 75%, and 100%) alongside a commercial feed (CF) as control group, on growth performance, feed utilization, carcass composition, nutrient excretion, and economic assessment in 180 Channa striata fingerlings (3.04 ± 0.01 g), allocated randomly in 18 tanks, across 6 treatments. CF achieved the highest growth, with a specific growth rate (SGR) of 1.72 ± 0.00. Among lab-prepared diets, 25% L. minor replacement (D2 diet) produced significantly (p < 0.05) superior growth performance with 1.56 ± 0.00 SGR, a satisfactory feed conversion ratio (FCR) (2.27 ± 0.01), and carcass protein deposition (15.75% ± 0.11%) compared to higher inclusion levels, which resulted in poor growth, higher FCR (3.66 ± 0.01–6.36 ± 0.25), increased nitrogen (864.34 ± 7.20–1139.4 ± 12.99 mg kg-¹ BW day-¹) and phosphorous excretion (215.62 ± 8.99–296.42 ± 2.95 mg kg-¹ BW day-¹). Economic analysis revealed that the D2 achieved the highest profit index (5.27), leaving CF (3.02) less profitable despite achieving the highest growth. Overall, the outcomes suggest that L. minor can serve as a cost-effective alternative protein source by effectively replacing up to 25% of the fish meal in the diets for C. striata fingerlings. However, it does not fully match the performance of CF under present conditions.