低聚木糖对奥尼罗非鱼肠道形态、菌群组成和抗嗜水气单胞菌感染的影响

选取960尾初始体重为(5.09±0.12)g的奥尼罗非鱼(Oreochromis niloticus×O.aureus),随机分为6组,分别投喂1种对照饲料和5种添加低聚木糖的试验饲料,添加量分别为0、200、400、600、800、和1 000mg/kg饲料,记作G0、G200、G400、G600、G800和G1000。饲养期为8周,每两周取样测定肠道双歧杆菌(Bifidobacterium)、乳酸杆菌(Lactobacillus)和大肠杆菌(E.coli)数量,4周和8周时取肠道样测定肠道形态。试验结束时注射嗜水气单胞菌(Aeromonas hydrophila)进行感染试验,计算96 h内的存活率。结果显示,4周和8周时,各添加组罗非鱼中肠皱襞面积和肌层厚度均显著高于对照组。饲料中添加低聚木糖对罗非鱼肠道双歧杆菌和乳酸杆菌数量有显著影响,与对照组相比,双歧杆菌数量在4周时G600和G800组显著增加(P<0.05),在6周时G400和G600显著增加(P<0.05);8周时,G800组罗非鱼肠道乳酸杆菌较对照组有显著增加(P<0.05);各添加组肠道大肠杆菌数量随养殖时间延长呈下降趋势,但各组之间在各时间段的差异没有达到显著水平(P>0.05)。注射嗜水气单胞菌96 h后,对照组的存活率为26.7%,低聚木糖添加组为78.3%～95.0%。结果表明,饲料中添加低聚木糖能改善肠道形态结构,显著提高奥尼罗非鱼肠道双歧杆菌和乳酸杆菌数量,有降低大肠杆菌数量的趋势,并提高罗非鱼抗嗜水气单胞菌感染的能力,添加600 mg/kg左右最合适。研究亮点:首次在饲料中添加低聚木糖饲喂奥尼罗非鱼幼鱼,动态取样,采用细菌培养方法,测定低聚木糖对奥尼罗非鱼在养殖期间不同时段肠道菌群的影响;采用组织切片技术,观察低聚木糖对奥尼罗非鱼肠道皱襞面积和肌层厚度的影响;并采用嗜水气单胞菌进行感染试验,了解低聚木糖对奥尼罗非鱼抗病能力的影响。

Effect of dietary xylooligosaccharides on intestinal histology and microflora of tilapia(Oreochromis niloticus×O.aureus) and resistance against Aeromonas hydrophila

This experiment was conducted to investigate the effects of dietary prebiotic xylooligosaccharides(XOS) levels on the intestinal histology,microflora,and disease resistance of the tilapia(Oreochromis niloticus×O.aureus).960 fishes with an initial weight of(5.09±0.12) g were randomly assigned to 6 groups.The fishes were respectively fed a basal diet and 5 diets supplemented with 200,400,600,800 and 1 000 mg/kg XOS,named G0(control),G200,G400,G600,G800 and G 1000.During 8 weeks feeding period,the number of intestinal microflora was measured every 2 weeks.Midgut was sampled in 4th and 8th week for histology analysis.At the end of feeding,the fish were infected with Aeromonas hydrophila.During 96 hours of artificial infection,the survival rate(SR) was measured.The results showed that in 4th and 8th week,compared with G0,the folding area and the muscle thickness of the intestine in the groups with XOS were significantly higher.Dietary XOS affected significantly the number of intestinal Bifidobacterium and Lactobacillus.Compared with G0,the number of Bifidobacterium in G600 and G800 was significantly higher(P<0.05) in 4th week,in G400 and G600 significantly higher(P<0.05) in 6th week.In 8th week,the number of Lactobacillus in G800 was significantly higher than that in G0(P<0.05).The number of E.coli in the groups with XOS tended to decrease with the feeding time in creasing,but the difference was not significant(P>0.05).After 96 hours of infection by Aeromonas hydrophila,SR in G0 was 26.7%,and that in the groups with XOS was from 78.3 to 95.0%.The results suggested that the supplementation of XOS into the practical diet could improve the intestinal histology,promote the intestinal bacteria,Bifidobacterium and Lactobacillus proliferation,while decrease the number of E.coli to some extent,and improve the resistance against Aeromonas hydrophila of tilapia(Oreochromis niloticus×O.aureus).