Abstract The use of low-gossypol cottonseed protein concentrate (CPC) as a replacement for fishmeal (FM) in the juvenile hybrid grouper (Epinephelus fuscoguttatus ♀ × Epinephelus lanceolatus ♂) was investigated concerning differences in growth performance, immune response, and intestinal microbiota among the dietary treatments. Hybrid grouper were fed a diet (isonitrogenous and isolipidic) with FM or FM replaced with either 20% (CPC20), 40% (CPC40) or 60% CPC (CPC60) for 10 weeks. At the end of the study, there were no significant differences in the weight gain rate, specific growth rate, survival rate, and feed intake of fish among the groups. However, the feed conversion ratio of fish in the CPC-containing groups was higher than that in the FM group and was significantly higher in the CPC40 and CPC60 group. The levels of immunity-related enzyme activities and gene expression in the fish intestine were also investigated. In the CPC-containing groups, the lysozyme activity and immunoglobulin M levels were significantly increased, while the superoxide dismutase and catalase activities were significantly reduced compared to the FM group. The mRNA expression of innate immune genes (MHC-II-β, TLR22, TNF-α1, IL-6, IFN-γ, and IL-10) of the distal intestine (DI) was significantly increased in CPC-fed fish; however, there was no significant change in the TGF-β1 expression. The bacterial community in the DI was analyzed by Next-Generation Sequencing, which showed no significant difference in alpha diversity among the four diet groups. At the family level, the relative abundance of Burkholderiaceae was significantly higher in the CPC20 group compared to the FM group, while the relative abundance of Bacteroidales S24–7 group and Lachnospiraceae was significantly higher in the FM group. The functional prediction of the microbiota indicated that the pathways of amino acid metabolism, xenobiotics biodegradation and metabolism were significantly more abundant in the CPC-containing groups than the FM group. In contrast, the pathways associated with genetic information processing (translation, replication and repair) were more prevalent in the FM group. These results demonstrated that although dietary CPC replacement of levels up to 60% did not significantly alter the growth performance in hybrid grouper, the immune responses were adversely influenced. Replacing FM with CPC had an important impact on microbial profiles but not on diversity.

中文翻译：

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低棉酚浓缩棉籽蛋白用作杂交石斑鱼幼鱼（Epinephelus fuscoguttatus ♀ × Epinephelus lanceolatus ♂）替代鱼粉：对生长性能、免疫反应和肠道微生物群的影响

摘要 研究了使用低棉酚浓缩棉籽蛋白 (CPC) 作为杂种石斑鱼幼鱼 (Epinephelus fuscoguttatus ♀ × Epinephelus lanceolatus ♂) 中鱼粉 (FM) 的替代品在生长性能、免疫反应和肠道微生物群方面的差异。饮食治疗。用 FM 或 FM 代替 20% (CPC20)、40% (CPC40) 或 60% CPC (CPC60) 的饲料（等氮和等脂）喂养杂种石斑鱼 10 周。研究结束时，各组鱼的增重率、比生长率、成活率和采食量均无显着差异。但含CPC组鱼的饲料转化率高于FM组，且在CPC40和CPC60组显着较高。还研究了鱼肠中免疫相关酶活性和基因表达的水平。与FM组相比，含CPC组溶菌酶活性和免疫球蛋白M水平显着升高，而超氧化物歧化酶和过氧化氢酶活性显着降低。CPC喂养的鱼的远端肠（DI）先天免疫基因（MHC-II-β、TLR22、TNF-α1、IL-6、IFN-γ和IL-10）的mRNA表达显着增加；然而，TGF-β1 表达没有显着变化。通过下一代测序分析了 DI 中的细菌群落，结果表明四个饮食组的 alpha 多样性没有显着差异。在家庭层面，与 FM 组相比，CPC20 组中伯克霍尔德菌科的相对丰度显着更高，而 FM 组中拟杆菌属 S24-7 组和毛螺菌科的相对丰度显着更高。微生物群的功能预测表明，含CPC组的氨基酸代谢、异生物质生物降解和代谢途径明显多于FM组。相比之下，与遗传信息处理（翻译、复制和修复）相关的通路在 FM 组中更为普遍。这些结果表明，虽然日粮 CPC 替代水平高达 60% 并没有显着改变杂交石斑鱼的生长性能，但免疫反应受到不利影响。