The study aimed to investigate the effects of dietary sodium butyrate (NaBT) supplementation on the gut health of largemouth bass (Micropterus salmoides) fed with a high soybean meal diet. Three isonitrogenous and isolipidic diets were formulated: a high fishmeal group (Control); a high soybean meal group (SBM), in which the 30% fishmeal protein in the Control diet was replaced by soy protein; and an NaBT group, in which 0.2% NaBT was added to the SBM diet. Each diet was fed to triplicate tanks (20 fish in each tank). After 8 weeks of feeding trial, the distal intestine and intestinal digesta of the fish in each treatment were sampled. The results showed that fishmeal replacement and NaBT supplementation did not affect fish growth performance. Dietary 0.2% NaBT supplementation improved intestinal morphology, increasing the villus width and villus height and reducing the width of lamina propria. The distal intestine of fish in the control and NaBT groups demonstrated lower activities of total superoxide dismutase (T-SOD) and glutathione peroxidase (GPx) and a lower malondialdehyde (MDA) content, compared with the fish in the SBM group. Moreover, the addition of 0.2% NaBT in the feed significantly decreased the expression of tumor necrosis factor α (TNF-α) and interleukin 1β (IL-1β) compared to the SBM diet. PCoA and UPGMA analyses based on weighted UniFrac distances demonstrated that intestinal microbial communities in the NaBT group were closer to those in the control group than to those in the SBM group. In addition, dietary 0.2% NaBT supplementation significantly increased the abundance of Firmicutes and Bacteroidetes and decreased the abundance of Tenericutes at the phylum level. Furthermore, the abundance of Bacteroides, Lachnospiraceae_unclassified, and Lachnospiraceae_uncultured was significantly increased, while that of Mycoplasma was significantly decreased in fish intestine at NaBT group at the genus level. In conclusion, dietary NaBT supplementation had beneficial roles in protecting the gut health of largemouth bass from the impairments caused by soybean meal.

该研究旨在调查膳食丁酸钠（NaBT）补充剂对高豆粕饲料喂养的大口黑鲈（ Micropterus salmoides ）肠道健康的影响。制定了三种等氮和异脂饮食：高鱼粉组（对照）；高豆粕组（SBM），其中对照日粮中的30%鱼粉蛋白被大豆蛋白替代； NaBT 组，其中在 SBM 饮食中添加 0.2% NaBT。将每种饲料喂入一式三份的水箱中（每个水箱中 20 条鱼）。饲养试验8周后，对各处理鱼的远端肠和肠食糜进行取样。结果表明，鱼粉替代和NaBT补充不会影响鱼的生长性能。膳食中添加 0.2% NaBT 可改善肠道形态，增加绒毛宽度和绒毛高度，并减少固有层宽度。与 SBM 组的鱼相比，对照组和 NaBT 组的鱼远端肠总超氧化物歧化酶 (T-SOD) 和谷胱甘肽过氧化物酶 (GPx) 活性较低，丙二醛 (MDA) 含量较低。此外，与SBM日粮相比，饲料中添加0.2% NaBT显着降低了肿瘤坏死因子α（TNF-α）和白细胞介素1β（IL-1β）的表达。基于加权 UniFrac 距离的 PCoA 和 UPGMA 分析表明，NaBT 组的肠道微生物群落比 SBM 组更接近对照组。此外，膳食中添加 0.2% NaBT 显着增加了厚壁菌门和拟杆菌门的丰度，并降低了门水平的软壁菌门的丰度。 此外，在属水平上，NaBT组鱼肠中拟杆菌属、毛螺菌科_未分类和毛螺菌属_未培养的丰度显着增加，而支原体丰度显着下降。总之，膳食中添加 NaBT 对于保护大口黑鲈的肠道健康免受豆粕造成的损害具有有益作用。