Abstract
Understanding of microbial communities inhabiting cattle vaginal tract may lead to a better comprehension of bovine physiology and reproductive health being of great economic interest. Up to date, studies involving cattle microbiota are focused on the gastrointestinal tract, and little is known about the vaginal microbiota. This study aimed to investigate the vaginal microbiome in Nellore cattle, heifers and cows, pregnant and non-pregnant, using a culture independent approach. The main bacterial phyla found were Firmicutes (~40–50%), Bacteroidetes (~15–25%) and Proteobacteria (~5–25%), in addition to ~10–20% of non-classified bacteria. 45–55% of the samples were represented by only ten OTUs: Aeribacillus, Bacteroides, Clostridium, Ruminococcus, Rikenella, Alistipes, Bacillus, Eubacterium, Prevotella and non-classified bacteria. Interestingly, microbiota from all 20 animals could be grouped according to the respiratory metabolism of the main OTUs found, creating three groups of vaginal microbiota in cattle. Archaeal samples were dominated by the Methanobrevibacter genus (Euryarchaeota, ~55–70%). Ascomycota was the main fungal phylum (~80–95%) and Mycosphaerella the most abundant genus (~70–85%). Hormonal influence was not clear, but a tendency for the reduction of bacterial and increase of archaeal populations in pregnant animals was observed. Eukaryotes did not vary significantly between pregnant and non-pregnant animals, but tended to be more abundant on cows than on heifers. The present work describes a great microbial variability in the vaginal community among the evaluated animals and groups (heifers and cows, pregnant and non-pregnant), which is significantly different from the findings previously reported using culture dependent methods, pointing out the need for further studies on this issue. The microbiome found also indicates that the vaginal colonization appears to be influenced by the gastrointestinal community.
Highlights
Cattle ranching has accompanied humankind for thousands of years, and today there are around one billion heads worldwide [1]
This is an important analysis that considers the number of species present in a given sample and their abundance, providing an estimate of the diversity of that sample—a low value of alpha diversity being attributed to communities dominated by only a few species, and a high value to communities dominated by a great variety of members
Our analysis shows that these bacteria are not among the major Operational Taxonomic Unit (OTU) found, and its dominance in studies involving cultivation can probably be explain by their rapid growth and low nutritional requirements, coupled with an insufficient knowledge of the vaginal microbiota
Summary
Cattle ranching has accompanied humankind for thousands of years, and today there are around one billion heads worldwide [1]. These animals are an important part of global economy—constituting a billion dollar market—especially for Brazil, the world’s larger beef exporter [1]. Despite the relevance of these animals, many aspects of their biology are still unknown, including the composition of the vaginal microbiota in cows. Few studies using culture dependent methods reported a low abundant microbiota, dominated by enterobacteria [7,8,9], but the real microbial composition remains to be defined
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