Fish farming artifact yeast culture, the role of yeast culture in aquaculture

【 Shuntian Classroom 】 Fish farming artifact yeast culture, the role of yeast culture in aquaculture and experimental data review【顺天课堂】养鱼人工酵母培养，酵母培养在水产养殖中的作用及实验数据综述

      Yeast culture (YC), as a natural fermentation product, has shown multiple effects in aquaculture in recent years, including replacing antibiotics, promoting growth, improving intestinal health, and enhancing immunity. This article combines multiple experimental data to systematically summarize its mechanism of action and practical application effects.酵母培养物（YC）作为一种天然发酵产物，近年来在水产养殖中显示出替代抗生素、促进生长、改善肠道健康、增强免疫力等多种作用。本文结合多项实验数据，系统总结其作用机理和实际应用效果。

1、 Promote the growth performance of aquatic animals1、促进水生动物生长性能

Improve specific growth rates and feed efficiency提高特定生长率和饲料效率

      Adding YC (0.07% -0.5%) to the feed of aquatic animals such as grass carp, flounder, and shrimp can significantly increase specific growth rate (SGR) and reduce feed efficiency. For example, adding 0.5% YC to grass carp feed can increase specific growth rates by 15% and reduce feed efficiency by 12%. In the experiment of blunt headed bream, the weight gain rate of the group fed with 2000 mg/kg YC continuously increased by 8.3% compared to the control group, and the optimization of feed efficiency was significant.草鱼、比目鱼、对虾等水产动物饲料中添加YC（0.07% ~ 0.5%）可显著提高特定生长率（SGR），降低饲料效率。例如，在草鱼饲料中添加0.5%的YC可使特定生长率提高15%，饲料效率降低12%。在钝头鲷试验中，连续添加2000 mg/kg YC组的增重率较对照组提高了8.3%，饲料效率优化显著。

      Research on Vannamei shrimp showed that adding 2% YC (B2 group) increased weight gain by 24% and reduced feed conversion rate (FCR) by 18%. In the grouper experiment, the survival rate of the 4% YC group (N2) was as high as 80%, significantly higher than the control group's 26.4%.对凡纳美对虾的试验表明，添加2%的YC （B2组）可使其增重提高24%，饲料转化率降低18%。在石斑鱼试验中，4% YC组（N2）的成活率高达80%，显著高于对照组的26.4%。

Relieve the negative impact of low-quality feed缓解低品质饲料的负面影响

      When replacing 20% of high-quality fish meal with low-quality fish meal in the feed of American eel, adding 0.1% YC can maintain a specific growth rate, and the height of intestinal villi and antioxidant capacity are close to the original level; But when the substitution ratio exceeds 30%, YC cannot completely offset the growth inhibition effect.在美洲鳗饲料中用低品质鱼粉替代20%的优质鱼粉时，添加0.1%的YC可保持一定的特定生长率，肠绒毛高度和抗氧化能力均接近原水平；但当取代率超过30%时，YC不能完全抵消生长抑制作用。

2、 Improve intestinal health and digestive function2、改善肠道健康和消化功能

Optimize the structure of gut microbiota优化肠道菌群结构

      YC improves intestinal microbiota balance by competitively inhibiting pathogen adhesion and promoting probiotic proliferation. For example, the proportion of Vibrio species in the gut of turbot has decreased from 90% to below 50%, with Bacillus becoming the dominant bacterial group. After adding 2% YC to Fenneropenaeus vannamei, the intestinal pathogenic bacteria Vibrio decreased, while beneficial bacteria such as Pseudomonas increased significantly. The abundance of lactobacilli and bifidobacteria in the intestinal tract of pearl gentian grouper increased, and the proportion of actinomycetes increased.YC通过竞争性抑制病原菌粘附和促进益生菌增殖来改善肠道菌群平衡。例如，大菱鲆肠道中弧菌种类的比例从90%下降到50%以下，芽孢杆菌成为优势菌群。凡纳滨对虾中添加2% YC后，肠道致病菌弧菌数量减少，有益菌如假单胞菌数量显著增加。珍珠龙胆石斑鱼肠道中乳酸菌和双歧杆菌丰度增加，放线菌比例增加。

Enhance intestinal morphology and digestive enzyme activity增强肠道形态和消化酶活性

      YC significantly increases the height and density of intestinal villi. Continuous feeding of the YC group resulted in a 25% increase in midgut villus density and an 18% increase in villus height in the flathead bream. In the shrimp experiment, the height and width of intestinal villi in the YC group increased by 20% and 15%, respectively. In addition, YC activates digestive enzymes through B vitamins and organic acids, such as increasing grass carp protease activity by 30% and lipase activity by 25%.

3、 Enhance immunity and disease resistance

Non-specific immune enhancement

      β - glucan and MOS in YC can activate macrophage and lysozyme activity. After feeding YC to Fenneropenaeus vannamei, serum lysozyme activity increased by 40% and superoxide dismutase (SOD) activity increased by 35%. In the grouper experiment, the total antioxidant capacity (T-AOC) of the 4% YC group increased by 50% compared to the control group, while the level of malondialdehyde (MDA) decreased by 30%.

Improvement in disease resistance and survival rate

      In the Vibrio parahaemolyticus challenge test, the survival rate of shrimp in the YC group was as high as 66.7%, while the control group was only 16.7%. The relative survival rate of pearl gentian grouper YC group against Vibrio infection increased to 80%, significantly higher than the control group.

4、 Optimize feed utilization and substitution potential

Alternative antibiotics and fish meal

      YC can replace antibiotics such as quinolones. The tilapia test showed no significant difference in weight gain rate compared to the antibiotic group, but it has stronger resistance to transport stress. In the low-quality fish meal substitution experiment, YC effectively alleviated enteritis caused by soybean meal and maintained intestinal barrier integrity.

Synergistic probiotic effect

      When Bacillus subtilis is combined with YC, the specific growth rate of pearl gentian grouper increases by 12%, the activity of intestinal digestive enzymes increases by 20%, and the concentration of ammonia nitrogen in water quality decreases by 30%.

5、 Application precautions and future directions

Dose and species differences

      The optimal amount of YC added varies depending on the species, such as 2% for shrimp and 4% for grouper. Excessive addition may lead to decreased palatability. In the experiment of blunt headed bream, the growth rate of the 2500 mg/kg group was lower than that of the control group, indicating the need for precise dosage control.

Production process and stability

      The active ingredients of YC, such as MOS and organic acids, are greatly affected by bacterial strains and fermentation processes, and require standardized production processes to ensure effectiveness.

Long term ecological impact

      Although YC is environmentally friendly and safe, the impact of long-term use on the microbial community in water bodies still needs to be evaluated. It is recommended to combine ecological prevention and control strategies such as biological flocculation technology (BFT).

conclusion 结论

      Yeast cultures significantly enhance the growth performance and disease resistance of aquatic animals through multiple mechanisms such as regulating gut microbiota, enhancing digestive enzyme activity, and activating immune pathways. Experimental data shows that it has broad prospects in replacing antibiotics, optimizing feed formulations, and promoting sustainable aquaculture.