This study aimed to investigate the effects of solid-state fermentation products of yeast (SFPY) on liver and intestinal health and disease resistance of common carp (Cyprinus carpio). A total of 200 common carp with an initial average weight of 2.55 ± 0.004 g were divided into 5 groups (4 replications per group and 10 fish per replication), and were fed with one of five diets, including a control diet and 4 diets supplemented with 2‰ (Y2), 3‰ (Y3), 4‰ (Y4), or 5‰ (Y5) SFPY, respectively, for 8 weeks. Results indicated that, the addition of SFPY to the diet of common carp did not affect the growth performance or survival rate of fish (P = 0.253). Interestingly, with the addition of SFPY, the triacylglycerol (TAG) content of the liver presented a linear decreasing tendency (P = 0.004), with significantly decreased in Y4 and Y5 groups (P = 0.035) compared with control. Serum lipopolysaccharide (LPS) content and diamine oxidase (DAO) activity presented a negative linear relationship with the addition of SFPY (P = 0.015, P = 0.030), while serum lipopolysaccharide binding protein (LBP) content first decreased and then increased (P < 0.001). The total antioxidant capacity (T-AOC) in the intestine of fish increased continuously with increasing SFPY supplementation (P = 0.026), reaching the highest level in Y5 group. The villus height in all experimental groups were significantly higher than that in the control group (P < 0.001). Furthermore, compared to the control, adding 3‰ SFPY to the control diet of common carp significantly increased the relative abundance of Fusobacteria (P = 0.018) and decreased that of Proteobacteria (P = 0.039) at phylum level, and increased the relative abundance of Cetobacterium (P= 0.018) and decreased that of Shewanella (P = 0.013) at genus level. Compared with the control, the relative mRNA expression level of spring viraemia of carp virus N protein (SVCV-n) in the kidney was lower than that of the control group without significance and bottomed out in Y4 group (P = 0.138). In conclusion, dietary SFPY enhanced the SVCV resistance capacity of common carp by improving liver and intestinal health and modulating the gut microbiota. Thus, SFPY is a potential feed additive to be used in aquaculture to reduce the huge economic loss of common carp due to SVCV disease. Based on liver TAG content and intestinal villus height, the optimal addition level of SFPY was 3.02‰ and 2.72‰, respectively.

中文翻译：

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酵母补充剂的固态发酵产物对肝脏和肠道健康的影响，以及鲤鱼 （Cyprinus carpio） 对春季病毒血症鲤鱼病毒的抵抗力


本研究旨在探讨酵母固态发酵产物 （SFPY） 对鲤鱼 （Cyprinus carpio） 肝脏和肠道健康和抗病性的影响。将初始平均体重为 2.55 ± 0.004 g 的鲤鱼共分为 5 组（每组 4 次重复，每次重复 10 条鱼），饲喂 5 种日粮中的一种，包括对照日粮和 4 种日粮补充 2‰ （Y2）、3‰ （Y3）、4‰ （Y4） 或 5‰ （Y5） SFPY， 分别持续 8 周。结果表明，在鲤鱼的饮食中添加 SFPY 不会影响鱼类的生长性能或存活率 （P = 0.253）。有趣的是，加入 SFPY 后，肝脏的三酰甘油 （TAG） 含量呈线性下降趋势 （P = 0.004），与对照组相比，Y4 和 Y5 组 （P = 0.035） 显著降低。血清脂多糖 （LPS） 含量和二胺氧化酶 （DAO） 活性与 SFPY 的添加呈负线性关系 （P = 0.015，P = 0.030），而血清脂多糖结合蛋白 （LBP） 含量先降低后升高 （P < 0.001）。随着 SFPY 添加量的增加，鱼肠道内总抗氧化能力 （T-AOC） 持续增加 （P = 0.026），在 Y5 组中达到最高水平。所有实验组的绒毛高度均显著高于对照组 （P < 0.001）。此外，与对照相比，在鲤鱼对照日粮中添加 3‰ SFPY 在门水平上显著增加了梭杆菌门的相对丰度 （P = 0.018） 和变形菌门的相对丰度 （P = 0.039），增加了鲸杆菌门的相对丰度 （P = 0.018） 和降低了希瓦氏菌的相对丰度 （P = 0.013） 在属水平上。与对照组相比，鲤鱼病毒N蛋白春季病毒血症（SVCV-n）在肾脏中的相对mRNA表达水平低于对照组，无显著意义，Y4组触底（P = 0.138）。综上所述，膳食 SFPY 通过改善肝脏和肠道健康和调节肠道菌群增强了鲤鱼的 SVCV 抵抗能力。因此，SFPY 是一种潜在的饲料添加剂，可用于水产养殖，以减少 SVCV 病害对鲤鱼的巨大经济损失。根据肝脏 TAG 含量和肠绒毛高度，SFPY 的最佳添加水平分别为 3.02‰ 和 2.72‰。