Fishmeal has long been a staple protein feedstuff for fish, but its global shortage and high price have prompted its replacement with alternative sustainable sources. In this experiment involving largemouth bass (a carnivorous fish), a new mixture of feedstuffs (45% poultry byproduct meal, 30% soybean meal, 15% blood meal, and 10% krill shrimp meal) was added to low (14.5%) fishmeal diets along with 0.0%, 0.5% taurine, 0.5% methionine, or 0.5% taurine plus 0.5% methionine (dry matter basis). The positive control diet [65.3% fishmeal (46% crude protein on dry matter basis)] and all low-fishmeal diets contained 40% true protein and 10% lipids. There were 3 tanks per treatment group (20 fish/tank). Fish with the mean initial body weight of 16.6 g were fed to satiety twice daily. Compared with the unsupplemented low-fishmeal group, supplementing either 0.5% methionine or 0.5% methionine plus 0.5% taurine to the low-fishmeal diet improved (P < 0.05) the growth, feed utilization, retention of dietary protein and lipids, and health of largemouth bass, reduced (P < 0.05) the occurrence of black skin syndrome from ~ 40 to ~ 10%. Histological sections of tissues from the fish with black skin syndrome showed retina degeneration, liver damage, and enteritis in the intestine. Compared with methionine supplementation, supplementing 0.5% taurine alone to the low-fishmeal diet did not affect the growth or feed efficiency of fish and had less beneficial effects (P < 0.05) on ameliorating the black skin syndrome. These results indicated that: (a) the basal low-fishmeal diet was inadequate in methionine or taurine; and (b) dietary supplementation with methionine was an effective method to improve the growth performance, feed efficiency, and health of largemouth bass. Further studies are warranted to understand the pathogenesis of the black skin syndrome in largemouth bass.

鱼粉长期以来一直是鱼类的主要蛋白质饲料，但其全球短缺和高价格促使其被替代的可持续来源替代。在这项涉及大嘴黑鲈（肉食性鱼类）的实验中，将一种新的饲料混合物（45% 家禽副产品粉、30% 豆粕、15% 血粉和 10% 磷虾虾粉）添加到低 (14.5%) 鱼粉中与 0.0%、0.5% 牛磺酸、0.5% 蛋氨酸或 0.5% 牛磺酸加 0.5% 蛋氨酸（干物质基础）一起的饮食。阳性对照日粮 [65.3% 鱼粉（46% 的干物质粗蛋白）] 和所有低鱼粉日粮均含有 40% 的真蛋白质和 10% 的脂质。每个处理组有 3 个鱼缸（20 条鱼/鱼缸）。平均初始体重为 16.6 克的鱼每天喂两次饱腹感。与未添加低鱼粉组相比，P  < 0.05) 大嘴 黑鲈的生长、饲料利用率、日粮蛋白质和脂质的保留以及健康，将黑皮综合征的发生率从~40% 降低到~10% ( P < 0.05)。黑皮肤综合征鱼的组织切片显示视网膜变性、肝损伤和肠道肠炎。与添加蛋氨酸相比，在低鱼粉日粮中单独添加0.5%牛磺酸不影响鱼类的生长或饲料效率，且有益效果较小（P < 0.05) 改善黑皮肤综合征。这些结果表明： (a) 基础低鱼粉日粮中蛋氨酸或牛磺酸不足；(b) 在日粮中添加蛋氨酸是提高大口黑鲈生长性能、饲料效率和健康的有效方法。需要进一步研究以了解大口黑鲈黑皮综合征的发病机制。