We previously demonstrated that dairy calves having access to drinking water since birth (W0) achieved greater body weight, fiber digestibility, and feed efficiency than those that first received drinking water at 17 d of age (W17). Since gut microbiota composition could be linked to growth and development of animals, the objective of this study was to examine the effect of offering drinking water to newborn calves on composition of bacteria in the gut using a fecal microbiota analysis. Fresh feces were collected directly from the rectum of calves in W0 (n = 14) and W17 (n = 15) at 2, 6, and 10 wk of age. All of the calves were fed pasteurized waste milk, weaned at 7 wk of age, and offered tap water according to the treatment. The DNA was sequenced using 16S rRNA gene-amplicon sequencing on an Illumina MiSeq system (Illumina Inc., San Diego, CA). The sequences were clustered into operational taxonomic units (OTU) with a 99% similarity threshold. Treatment effects on α-diversity indices and relative abundance of the 10 most abundant genera were analyzed using GLIMMIX procedure of SAS (SAS Institute Inc., Cary, NC). Statistical significance (q-value) of treatment effects on the 50 most abundant OTU was determined with a false discovery rate analysis. At 2 wk of age, W0 had a greater number of observed OTU (5,908 vs. 4,698) and species richness (Chao 1 index) than W17. The number of OTU and richness indices increased from wk 2 to 6, but the increment of W17 was greater than that of W0. The Shannon and inverse-Simpson indices increased linearly with age, but no difference was observed between W0 and W17 at any time point. The Firmicutes to Bacteroidetes ratios were also similar at every time point but decreased markedly when calves were weaned. The relative abundance of genera Faecalibacterium and Bacteroides was greater in W0 than W17 at 2 wk of age. The genus Faecalibacterium continued to be more abundant in W0 than W17 at 6 wk of age but had similar abundance 3 wk after weaning (10 wk of age). The abundance of Faecalibacterium at wk 6 was positively correlated with apparent total-tract digestibility of acid detergent fiber at 10 wk of age. Calves receiving water since birth had greater abundance of OTU related to Faecalibacterium prausnitzii, and Bifidobacterium breve at 6 wk of age (q < 0.085). These species are known to improve growth in preweaned calves. The abundance of none of the genera and OTU was different between W0 at W17 at 10 wk of age (q > 0.100). Overall, beginning to offer drinking water at birth has a potential to modulate gut microbiota composition and thereby positively affect performance of young dairy heifer calves (≤10 wk of age).

中文翻译：

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在出生时开始提供饮用水会增加断奶前小牛肠道中的物种丰富度以及费氏杆菌和双歧杆菌的含量。

我们以前的研究表明，自出生（W0）以来可以接触饮用水的奶牛犊，比在17 d时首次获得饮用水的犊牛（W17）具有更高的体重，纤维消化率和饲料效率。由于肠道菌群的组成可能与动物的生长发育有关，因此本研究的目的是使用粪便菌群分析研究为新生犊牛提供饮用水对肠道细菌组成的影响。在第2、6和10周龄，分别从W0（n = 14）和W17（n = 15）的小牛直肠中收集新鲜的粪便。给所有小牛喂食经巴氏消毒的废牛奶，在7周龄时断奶，并根据处理情况提供自来水。在Illumina MiSeq系统（Illumina Inc.，圣地亚哥，加利福尼亚）上使用16S rRNA基因-amplicon测序对DNA进行测序。将序列聚类为具有99％相似性阈值的操作分类单位（OTU）。使用SAS（SAS Institute Inc.，Cary，NC）的GLIMMIX程序分析了对10个最丰富属的α多样性指数和相对丰度的处理效果。用错误发现率分析确定了对50个最丰富OTU的治疗效果的统计显着性（q值）。在2周龄时，W0的观察到的OTU数量（5,908对4,698）和物种丰富度（Chao 1指数）比W17大。OTU的数量和丰富度指数从wk 2增加到6，但是W17的增量大于W0。香农指数和辛普森反指数随年龄线性增加，但在任何时间点，W0和W17之间均未观察到差异。在每个时间点，硬毛虫与拟杆菌的比率也相似，但是当犊牛断奶时，其比率显着下降。在2周龄时，W0中的Faecalibacterium和Bacteroides属的相对丰度高于W17。在6周龄时，Faecalibacterium属的W0继续比W17丰富，但断奶后3周周龄（10周龄）的丰度相似。6周龄时，产杆菌的丰度与酸性洗涤剂纤维的表观总消化率呈正相关。出生后接受水的犊牛在6周龄时与普氏杆菌和短双歧杆菌有关的OTU含量较高（q <0.085）。已知这些物种可改善断奶小牛的生长。在10周龄（w> 0）时，W0在W17时，属和OTU的丰度均不同。100）。总体而言，出生时开始提供饮用水有可能调节肠道菌群组成，从而对年轻的乳牛小母牛（年龄≤10wk）产生积极影响。