生物絮团养殖模式下益生菌添加对异育银鲫生长、消化酶活性及肠道组织结构的影响

前期研究表明,生物絮团技术(biofloc technology,BFT)适于异育银鲫(Carassius auratus gibelio)养殖。为进一步优化BFT养殖模式,本研究设置3个实验组:BFT模式下EM菌添加组(BB组)、枯草芽孢杆菌(Bacillus subtilis)添加组(BI组)和BFT对照组(B组),以均体重(1.60±0.50)g的异育银鲫为研究对象,探讨BFT模式下外源添加益生菌对养殖动物生长、消化酶活性及肠道组织结构的影响。结果表明:(1)益生菌添加组异育银鲫增重率和特定生长率显著高于对照组(P0.05),BB和BI组的增重率分别提高了216.70%和184.04%,特定生长率分别提高了141.18%和125.49%,BB和BI组间差异不显著(P0.05);(2)益生菌添加组(BB组和BI组)的消化酶(淀粉酶、脂肪酶和胃蛋白酶)活性均显著高于对照组(B组)(P0.05)。益生菌添加组间,BB组淀粉酶活性显著高于BI组(P0.05),脂肪酶和胃蛋白酶活性亦高于BI组,但差异不显著(P0.05);(3)益生菌添加组肠道肌层厚度和黏膜下层厚度显著高于对照组(B组)(P0.05),BB组异育银鲫肠道黏膜皱襞高度和皱襞间质宽度与BI和对照组相比,均无显著差异(P0.05)。研究表明,BFT养殖模式下外源添加益生菌可以更好地促进异育银鲫生长。

Effects of probiotic addition on the growth performance, digestive enzyme activity, and intestinal morphology of gibel carp (Carassius auratus gibelio) cultured using biofloc technology

Probiotics have been defined as live microorganisms, which confer health benefits to the host when administered in adequate amounts. The probiotics used in aquaculture commonly include effective microorganisms (EM bacteria), Bacillus sp. and Lactobacillus sp. The biofloc technology (BFT) is a zero-water exchange and eco-friendly aquaculture system. The BFT can recycle nutrient by introducing additional carbon source to culture water in order to stimulate the growth of heterotrophic bacteria that convert ammonia into microbial biomass. The microbial biomass will further aggregate with other microorganisms and particles to form bioflocs. The bioflocs contain a heterogeneous mixture of diatoms, macroalgae, food and fecal remnants, exoskeletons, bacteria, invertebrates, and other microorganisms. The bioflocs can maintain good water quality, increase fish growth performance, reduce feed cost by recycling feed residues and fecal excrements, aid enzymatic activity, and enhance innate immunity and disease resistance. Meanwhile, the BFT can minimize water exchange to save labor and environmental costs, and reduce water usage and waste generated in aquaculture. It can also avoid drug abuse for disease control, because of the key microorganism in the bioflocs. The BFT has the potential to be used widely in aquaculture. Gibel carp (Carassius auratus gibelio) is one of important freshwater species farmed in China, and it is a representative species of mudflat cultured fish. However, with the rapid development of aquaculture, the waste of water resources, pollution, and diseases seriously affected the sustainable development and aquaculture efficiency of gibel carp. Our previous studies showed that the BFT can be used in gibel carp culture and that it has positive effects on the growth performance and immune response of gibel carp. To further optimize the BFT system in gibel carp culture, a 35-day feeding experiment was conducted to evaluate the effects of probiotics on the growth performance, digestive enzyme activities, and intestinal morphology of gibel carp cultured using the BFT. A total of 1800 normal gibel carps with a mean body weight of 1.60 g were randomly assigned to nine ponds (3.0 m×1.0 m×0.8 m) as three experimental treatments, including the EM bacteria addition group in BFT system (BB), Bacillus subtilis addition group in BFT system (BI), and BFT without any probiotics addition (B). The results revealed the followings (1) Compared with those of the control group, weight gain and specific growth of gibel carp in the BB and BI groups were significantly higher (P<0.05); the weight gain in the BB and BI groups increased by 216.70% and 184.04%, respectively. Furthermore, the specific growth increased by 141.18% and 125.49%, respectively. The weight gain and specific growth in BB group were higher but no significantly different from those in BI group (P>0.05). These results indicate that the addition of probiotics to BFT system can promote the growth of gibel carp. Additionally, compound bacteria (EM bacteria) addition showed better efficiency than the addition of single strain B. subtilis. (2) The activity of digestive enzymes (amylase, lipase and protease) in the probiotics addition groups (BB and BI) was significantly higher than those in control group (P<0.05), and the highest activities were observed in BB group. The activity of amylase in BB group was significantly higher than that in BI group (P<0.05). (3) The thickness of muscularis and submucosa of gibel carp gut in the probiotics addition groups was significantly higher than those in control group (P<0.05). The mucosal fold height and fold mesenchyme width of gibel carp gut were not significantly different among the BB, BI, and control groups (P>0.05). The results suggest that the addition of probiotics can promote growth of gibel carp and improve their intestinal digestive enzyme activities. Furthermore, the addition of probiotics can also affect the intestinal morphology of gibel carp cultured in BFT system. This study provides some valuable information to promote the usage of BFT in aquaculture.