Effect of flavanone rich lemon peel extract on feed intake and growth of Labeo rohita (Hamilton, 1822) fingerlings reared at low temperature recirculatory aquaculture system

Abstract

An 8-week experiment was conducted to study the effect of dietary lemon peel extract on feed intake and growth of Labeo rohita (rohu) fingerlings reared at low temperature (18 ± 1 °C). As a preliminary study, the antioxidant activity of lemon peel extract from water and ethanol was performed using DPPH, TPC, and FRAP assays, and found that the antioxidant activity in all three assays was higher for ethanol extract (25 mg L−1). Five isonitrogenous (300.0 g kg-1) and isocaloric (16.10 MJ kg−1) practical diets with varying levels of ethanol lemon peel extract viz, control (0.0 g kg−1 lemon peel extract), LPE2.5 (2.5 g kg−1 lemon peel extract), LPE5.0 (5.0 g kg−1 lemon peel extract), LPE10 (10.0 g kg−1 lemon peel extract), LPE20 (20.0 g kg−1 lemon peel extract) were prepared. The average initial body weight of the experimental animal was 10.30 ± 0.5 g, and the experiment was conducted in a low temperature (18 ± 1 °C) recirculatory aquaculture system (RAS) with a flow rate of 1.5 L min−1. The results showed that dietary lemon peel extract (LPE) supplementation increased the feed intake and growth performance in rohu fingerlings (p < 0.05). Fish fed with 5.0 g kg−1 LPE exhibited the best growth rates, thermal growth coefficient (TGC), and feed conversion (p < 0.05); however, TGC was similar in LPE5.0 and LPE10 fed groups (p > 0.05). Protease and aminotransferase enzyme activities positively correlated with growth rates (p < 0.05). Dietary LPE supplementation significantly augmented the hepatic malate dehydrogenase, citrate synthase, superoxide dismutase, and catalase activities (p < 0.05). From these results, it can be concluded that dietary supplementation of lemon peel extract at 5–10 g kg−1 level had positive effects on feed intake and metabolic activities of rohu reared at low temperature.