Effects of Lysine-Supplemented Groundnut Cake Diets on Growth Performance and Carcass Quality of Heterobranchus longifilis fingerlings

Abstract

Aquaculture plays a vital role in meeting the increasing demand for high-quality animal protein. However, feed costs account for over 50% of production expenses, limiting profitability and sustainability. Locally available plant protein sources such as groundnut cake offer a cost-effective alternative, but their use is constrained by deficiencies in essential amino acids, particularly lysine. This study evaluated the effects of lysine-supplemented groundnut cake–based diets on the growth performance and carcass quality of Heterobranchus longifilis fingerlings. Fingerlings (mean weight 1.54 g) were stocked at 15 fish per 60-L circular plastic tank and assigned to six experimental diets in triplicate. Diets included a fishmeal-based control (GFM), groundnut cake without lysine (GL0), and four lysine-supplemented diets: GL1 (0.25 g/kg), GL2 (0.5 g/kg), GL3 (0.75 g/kg), and GL4 (1.0 g/kg). All diets contained approximately 35% crude protein and were fed for 8 weeks. Mean weight gain was highest in GL2 (4.05 g), followed by GL3 (3.31 g), GL0 (2.81 g), GL4 (2.67 g), and GL1 (2.25 g). GL2 also recorded the highest specific growth rate (0.63% day⁻¹), best feed conversion ratio (2.15), and protein efficiency ratio (1.48). Carcass protein content was highest in GL3 (56.76%), followed by GL2 (47.95%). Lysine supplementation significantly improved growth, feed utilization, and carcass composition, with 0.5 g/kg (GL2) identified as the optimum inclusion level.