The main purpose of the agriculture circular economy is waste recycling with the intended goal of economic efficiency and environmental protection. In this study, the potential use of lemon peel, an agricultural waste, as a functional feed additive in aquafeed was evaluated by estimating the effects of fermented lemon peel (FLP) supplementation in diet on the growth, immune responses, and intestinal morphology of Asian sea bass, Lates calcarifer. Lemon peel was fermented by Lactobacillus plantarum. Basal diet was supplemented with 0%, 1%, 3%, and 5% FLP. Four experimental diets were each fed in triplicate to juvenile Asian sea bass (initial weight: 11.42 ± 0.39 g) in a recirculation rearing system for 8 weeks. Final weight, weight gain, feed intake, and survival were similar (p > 0.05) among all dietary treatments. Plasma lysozyme activity was higher in fish fed the diet with 3% FLP than that in fish fed the diet with 5% FLP. Hepatic thiobarbituric acid-reactive substance values were lower in fish fed diets with ≤3% FLP than that in fish fed the diet with 5% FLP. Fish fed diets with 1% and 3% FLP showed a tight lamina propria (LP) in microvilli compared with fish fed diets with 0% and 5% FLP. The microvilli area/height ratio was higher in fish fed diets with 0% and 5% FLP than that in fish fed diets with 1% and 3% FLP. The minimum level obtained from the second-order polynomial regression model were 0.26 % for microvilli area and area/height ratio. Results indicate that diets supplemented with 1 %–3 % fermented lemon peel can improve intestinal health for Asian sea bass. However, 5% FLP supplementation may lead to low immune response and high oxidative stress.

农业循环经济的主要目的是废物回收利用，其预期目标是经济效益和环境保护。在本研究中，通过评估在日粮中添加发酵柠檬皮 (FLP) 对亚洲人的生长、免疫反应和肠道形态的影响，评估了柠檬皮（一种农业废弃物）作为水产饲料中功能性饲料添加剂的潜在用途。鲈鱼，Lates calcarifer。柠檬皮是由植物乳杆菌发酵而成. 基础饮食补充有 0%、1%、3% 和 5% 的 FLP。在循环饲养系统中，将四种实验日粮每份一式三份喂给亚洲鲈鱼幼鱼（初始重量：11.42 ± 0.39 克），持续 8 周。在所有饮食处理中，最终体重、体重增加、采食量和存活率相似（p > 0.05）。饲喂含 3% FLP 饲料的鱼的血浆溶菌酶活性高于饲喂含 5% FLP 饲料的鱼。饲喂≤3% FLP 的鱼的肝脏硫代巴比妥酸反应物质值低于饲喂5% FLP 的鱼。与含 0% 和 5% FLP 的鱼饲料相比，含 1% 和 3% FLP 的鱼饲料在微绒毛中显示出紧密的固有层 (LP)。0% 和 5% FLP 的鱼饲料中的微绒毛面积/高度比高于 1% 和 3% FLP 的鱼饲料。对于微绒毛面积和面积/高度比，从二阶多项式回归模型获得的最低水平为 0.26%。结果表明，添加 1%–3% 发酵柠檬皮的日粮可以改善亚洲鲈鱼的肠道健康。然而，5% 的 FLP 补充剂可能会导致低免疫反应和高氧化应激。