http:∥xuebao.gxnu.edu.cn

表 4 Alpha 多样性指数分析结果

Tab. 4 Alpha diversity index

样本组别

多样性指数值

Ace Chao1 Shannon Simpson

MA 313.14±5.99 319.61±5.47 3.62±0.09

ab

0.06±0.01

ab

MB 314.46±3.37 315.88±3.48 3.72±0.16

ab

0.06±0.01

ab

MC 310.67±4.84 315.27±6.40 3.38±0.14

b

0.10±0.01

ab

MD 307.23±20.01 305.31±25.97 3.26±0.46

ab

0.15±0.08

a

ME 311.10±8.92 318.39±8.20 3.76±0.19

ab

0.15±0.08

a

MF 304.13±8.34 307.57±8.07 3.87±0.07

a

0.05±0.01

b

注:同列数据肩标小写字母相邻表示差异显著(P<0.05),小写字母相间表示差异极显著(P<0.01)。

2.3.2 肠道菌群 Beta 多样性分析

肠道菌群 Beta 多样性的主坐标分析(PCoA)和无度量多维标定法(NMDS)分析结果见图 4。 将数据

以点的形式反映在二维坐标图上,样本距离越近,表示物种组成结构越相似。 6 个组样本极大程度聚集在

一起,微生物群落结构的差异显著(P>0.05),表明 6 个组样本的微生物群落结构具有较高的相似性。

点分别表示各样品;不同颜色代表不同分组;横、纵坐标为导致样品间差异最大的 2 个特征值,以百分数的形式体现主要影响程度

图 4 PCoA 和 NMDS 分析结果

Fig. 4 PCoA and NMDS analysis chart

3 讨论

3.1 BCAAs 比例对攸县麻鸭肠道菌群组成的影响

肠道微生物主要是指肠道细菌,由有益菌、致病菌及中性菌构成,肠道细菌种群多达 500 种,但这些种

主要归属于少数的几个门类[18]

。 研究发现,厚壁菌门和拟杆菌门是单胃大型动物与小型动物肠道的两大

优势门类[18]

。 除去以上两大优势门类,鼠肠道中的主要菌群还有变形菌门与脱铁杆菌门[19]

,反刍动物和

鸡肠道中主要菌群还有变形菌门[20-21]

。 本研究中,两大优势门类为厚壁菌门和拟杆菌门,这与前人研究

结果[18-21]相一致,第三大优势门类为变形菌门,与反刍动物和鸡肠道主要菌群更为一致。 以上结果表明,

动物肠道的优势门类不会被轻易改变,但饲粮中添加 BCAAs 会对其中部分主要菌门有一定的影响。 另有

研究指出,15 月龄小鼠肠道中 BCAAs 补充组的拟杆菌门丰度较对照组下降3.9%,厚壁菌门丰度上升

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广西师范大学学报(自然科学版),2022,40(2)

3.62%,变形菌门作为其第三优势门类在补充组中的丰度远远低于对照组[17]

,而变形菌门中通常包含较多

的致病菌,因此,补充 BCAAs 可能有助于降低肠道菌群中的致病菌。 结合本研究,ME 组变形菌门丰度最

低且显著低于 MD 组,可以推测 BCAAs 中 Leu 比例在三者中为 37% ~40%时,更有益于攸县麻鸭的肠道健

康。 本研究还发现 MF 组放线菌门丰度显著高于 MA 组,放线菌门中通常包含较多的共生菌与益生菌,所

以 MF 组可能更有益于攸县麻鸭肠道菌群。

属水平上,BCAAs 比例对丰度前 10 的菌属均无显著影响,然而各组间仍有一定差异。 拟杆菌是肠道

中的共生菌,为身体提供必需的营养,在 MC 与 MF 组中丰度最高;脱硫弧菌是常见的致病菌,在 MA 组的

丰度最高。 BCAAs 可以被肠腔内的细菌利用[22-24]

,提示它们可能参与调节肠道菌群的组成。 在对小鼠的

研究中,发现 BCAAs 能够影响其肠道菌群的结构,并增加潜在益生菌双歧杆菌的丰度和降低致病菌肠杆

菌的比例[17]

。 本研究中 MF 组出现较多的双歧杆菌。 此外,猪的低蛋白饮食降低了肠道乳酸菌水平,但

BCAAs 平衡显著改善了乳酸菌的增殖[25]

;Ile 促进了鲤鱼肠中乳酸杆菌和芽孢杆菌的生长,抑制了气单胞

菌和大肠杆菌的生长[26]

。 然而对仔猪的研究中却发现 BCAAs 补充组与正常蛋白组的结肠微生物菌群没

有差异[22]

。 以上表明,BCAAs 对肠道菌群一定是有影响的,得到不一致的结果可能与动物品种、饲料组成

和 BCAAs 添加水平以及比例等问题有关。 因此,需要进一步深入研究来揭示 BCAAs 对机体肠道菌群的

影响。

3.2 BCAAs 比例对攸县麻鸭肠道菌群结构与多样性的影响

Yang 等[17]研究指出,补充 BCAAs 使小鼠肠道微生物多样性更丰富;文献[22-24]认为,BCAAs 通过

被肠道中细菌利用进而可能参与肠道微生物种类和多样性的调节。 但目前没有发现 BCAAs 比例对肠道

菌群影响的研究。 在本研究中,Alpha 多样性分析结果表明,6 组 Ace 和 Chao1 指数无显著差异(即 6 组具

有相同的物种丰度),而 MF 组 Shannon 指数显著大于 MC 组,Simpson 指数极显著小于 MC 组和 MA 组。

在相同物种丰度条件下,Shannon 指数越大,Simpson 指数越小,说明物种多样性越高,由此可见,在本研究

条件下,MF 组具有最高的微生物多样性,MC 组肠道微生物多样性最低。 在 Beta 多样性分析中,PCoA 与

NMDS 分析都是采取降维的思想对多样本数据进行定位、分析和归类,而 NMDS 分析克服了以前排序方法

(包括 PCoA 在内)的缺点,更具有可靠性。 结合 OTU 聚类分析发现,虽然 MD 组具有一特有的 OTU,但 6

组微生物菌落结构仍具有较高的相似性,表明不同 BCAAs 比例在该研究条件下没有对攸县麻鸭的肠道菌

群结构造成影响。

4 结论

63 日龄攸县麻鸭盲肠的核心菌群是拟杆菌门、厚壁菌门、变形菌门,BCAAs 比例显著影响变形菌门及

放线菌门,当亮氨酸、缬氨酸、异亮氨酸的质量比 m(Leu) ∶ m(Val) ∶ m(Ile)= 1 ∶ 0.9 ∶ 0.8 时,攸县麻鸭

盲肠微生物物种多样性最高。

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Effect of Dietary Branched-chain Amino Acid Ratio on Intestinal

Flora of 28-63 Days Old Youxian Duck

SUN Yue

1,2,3

, DAI Qiuzhong

2,4

, JIANG Guitao

2,4

, HUANG Xuan

2,4

,

LI Chuang

2,4

, DENG Ping

2,4

, SUN Tao

1,3∗

(1. College of Life Science, Guangxi Normal University, Guilin Guangxi 541006, China; 2. Hunan Institute of

Animal Science and Veterinary Medicine, Changsha Hunan 410131, China; 3. Key Laboratory of Ecology of Rare and

Endangered Species and Environmental Protection (Guangxi Normal University), Ministry of Education, Guilin

Guangxi 541006, China; 4. Hunan Engineering Research Center of Poultry Production Safety, Changsha Hunan 410128, China)

Abstract: A single factor experiment was adopted to investigate the effects of dietary branched-chain Amino Acid

ratio flora of 28-63 days old Youxian duck. 504 Youxian ducks of 28 day-old and healthy and similar in weight

were randomly allocated to 6 groups with 6 replicates each group and 14 in each replicate. Six diets with leucine,

valine and isoleucine ratios of 1 ∶ 0.4 ∶ 0.3 ( group MA), 1 ∶ 0.5 ∶ 0.4 ( group MB), 1 ∶ 0.6 ∶ 0.5 ( group

MC), 1 ∶ 0.7 ∶ 0.6(group MD), 1 ∶ 0.8 ∶ 0.7(group ME) and 1 ∶ 0.9 ∶ 0.8 (group MF) were avilable. The

experiment lasted for 35 days. At the end of the feeding experiment, one duck was selected from each replicate of

each treatment to collect cecal contents, and the cecal microbial structure and flora diversity were detected and

analyzed by 16S rDNA sequencing technology. The results show that: 1) There are 344 identical OTUs in the 6

groups, and only one unique OTU existed in group MD. 2) At the phylum level, the core flora are Bacteroidetes,

Firmicutes and Proteobacteria. At the genus level, Bacteroides and Desulfovibrio are the dominant genera; 3)

The results of comparion among the 6 groups show that, the abundance of Proteobacteria in group MD is

significantly higher than that in group ME ( P < 0. 05), and the abundance of Actinomycetes in group MF is

significantly higher than that in group MA (P<0.05); 4) There is no significant difference in Ace index and

Chao1 index among the 6 groups, however, the Shannon index in group MF is significantly higher than that in

group MC (P<0.05), and Simpson index in group MC is significantly higher than that in group MF (P<0.01)

and significantly higher than that in group MA (P<0.05). In summary, the core flora of the cecum of 63-day-old

Youxian duck is Bacteroides, Firmicutes, and Proteobacteria. The proportion of branched-chain amino acids in

diets significantly affects the Proteobacteria and Actinomycetes. When the ratio of mleucine, valine and

isoleucine is 1 ∶ 0.9 ∶ 0.8, the microbial species diversity of the cecum in Youxian duck is the highest.

Keywords: branched-chain amino acid; Youxian duck; intestinal flora; species abundance; species diversity

(责任编辑 马殷华)

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