Koi carp (Cyprinus carpio) are well-known and highly valuable fish in the international ornamental fish community that have been plagued by Aeromonas veronii infections in recent years. Some A. veronii infections are serious enough to cause death. Lactobacillus plantarum, a probiotic, is one of the most environmentally friendly and safe alternatives to antibiotics for use as a feed additive for aquatic animals such as fish. The present study investigated the effects of L. plantarum C20015 on growth performance, immune responses, and eradication of A. veronii infection in koi carp. During a 6-week feeding experiment in an indoor aquarium and a 14-day A. veronii artificial infection experiment, a control diet group was fed with untreated feed twice a day, while experimental groups were given different concentrations of L. plantarum in their feed. The results indicated that the specific growth rate and percent weight gain of fish were significantly higher in the experimental groups than in the control diet group (P < 0.05). The activity of superoxide dismutase (SOD), peroxidase (POD), and lysozyme (LZM) and the levels of IgM antibody were significantly higher in the L. plantarum–supplemented groups than in the control diet group, and the enzymatic activity in the 10⁸ CFU/g C20015 group was higher than that in the 10⁷ CFU/g C20015 and 10⁹ CFU/g C20015 groups (P < 0.01). In contrast, alkaline phosphatase (AKP) activity in the experimental groups was the highest at 42 days. All fish in the control diet group died 7 days after A. veronii infection. After 14 days, the relative percent survival (%, RPS) of the fish in the L. plantarum–supplemented groups was significantly higher than that of the fish in the control group, and the 10⁸ CFU/g C20015 group had the highest RPS. Therefore, we first reported that fish fed with 108 CFU/g of L. plantarum C20015 could promote food intake and growth for koi carp.

锦鲤（Cyprinus carpio）是国际观赏鱼界中的知名和极有价值的鱼，近年来一直受到维罗纳气单胞菌感染的困扰。某些维罗纳弧菌感染严重到足以导致死亡。益生菌植物乳杆菌是抗生素的最环保，最安全的替代品之一，可作为鱼类等水生动物的饲料添加剂。本研究调查了L. plantarum C20015对锦鲤生长性能，免疫反应和根除A. veronii感染的影响。在室内水族馆进行的为期6周的喂养实验和14天的拟南芥中在人工感染实验中，对照饮食组每天饲喂未经处理的饲料两次，而实验组的饲料中则添加了不同浓度的植物乳杆菌。结果表明，实验组鱼的比生长速率和体重增加百分比显着高于对照组饮食组（P < 0.05）。在补充植物乳杆菌的组中，超氧化物歧化酶（SOD），过氧化物酶（POD）和溶菌酶（LZM）的活性以及IgM抗体的水平显着高于对照饮食组，而在10个饮食组中的酶促活性⁸ CFU / g C20015组高于10 ⁷ CFU / g C20015和10 ⁹CFU / g C20015组（P < 0.01）。相反，实验组中碱性磷酸酶（AKP）活性在42天时最高。对照饮食组中的所有鱼类均在Veronii感染后7天死亡。14天后，补充植物乳杆菌的鱼的相对存活百分率（％，RPS）显着高于对照组鱼，并且10 ⁸ CFU / g C20015组的RPS最高。因此，我们首先报道了以108 CFU / g的植物乳杆菌C20015喂养的鱼可以促进锦鲤的食物摄入和生长。