Abstract
BACKGROUND: High dietary protein levels in aquafeeds lead to increased nitrogenous waste, which requires the development of sustainable feeding strategies that balance growth performance with environmental responsibility. OBJECTIVES: This study calculated the ratio of essential amino acids to lysine and investigated whether dietary protein could be reduced in feeds for Lvpan abalone (Haliotis discus hannai♀ × Haliotis fulgens♂) by lysine supplementation. METHODS: Five diets were formulated to be isoenergetic: a control diet (CP27, 27% crude protein), 2 low-protein diets (CP23 and CP19, 23% and 19% CP, respectively), and their lysine supplementation counterparts (CP23 + AA and CP19 + AA). After an 84-d feeding trial (initial abalone weight, 19.49 ± 0.52 g), the growth, digestibility, nitrogen excretion, hepatic transaminases, muscle composition, water-holding capacity, texture, and volatile profile were measured. RESULTS: The CP23 + AA diet maintained growth performance, improved apparent protein digestibility, and decreased nitrogen excretion compared with the control (P < 0.05). In contrast, the CP19 + AA diet reduced growth (P < 0.05). Lysine supplementation in the CP23 + AA group resulted in an increase in transaminase activity compared with the CP23 group, but it was not statistically significant (P > 0.05). Transaminase activity was greater in the CP19 + AA group than in the unsupplemented CP19 group (P < 0.05). CONCLUSIONS: A 4% reduction in dietary protein, when supplemented with lysine, demonstrates potential for sustainable abalone aquaculture through sustained growth and product quality coupled with reduced nitrogenous waste production.