Abstract
Reproductive performance is paramount to the success of livestock production enterprises focused on lamb meat production. Reproductive success is influenced by various factors, possibly including the reproductive tract microbial communities present at the time of copulation and throughout pregnancy. There are few publications that identify the vaginal microbial communities of livestock, and even fewer exist for sheep. To compare ewe vaginal microbial communities, vaginal swabs were taken from 67 Hampshire and Hampshire X Suffolk crossbred ewes from the Iowa State University sheep farm at a pre-breeding time point (S1) and after pregnancy testing (S2). Animals that were determined pregnant were sampled again within a few days of expected parturition (S3). DNA was extracted from these swabs, and 16S rRNA gene Illumina MiSeq amplicon sequencing was conducted to fingerprint the bacterial communities found within this system. Pre-breeding time point samples showed no differences in community structure between animals later found to be pregnant or non-pregnant, but significant changes were detected in species richness (Chao; P < 0.001) and species diversity (Shannon; P < 0.001) at the second sampling time point. A higher microbial diversity within the S2 time point samples may suggest a more stable environment driven by pregnancy, as this increased diversity is maintained in pregnant animals from the S2 to the S3 time point. Additionally, several bacterial phylotypes, such as Mannheimia, Oscillospiraceae-like OTUs and Alistipes, were more abundant at either the S1 or S2 time points in animals that established pregnancy, suggesting a beneficial effect on pregnancy outcome. This study identifies changes within the microbial communities of the ewe vagina before and during gestation and offers inferences on how these changes may impact pregnancy outcome. Information presented herein offers new knowledge about sheep vaginal microbial communities and serves as a starting point to help guide researchers to improve sheep reproductive performance in the future.
Highlights
Reproductive success is an important determinant of profitability for commercial sheep production enterprises focused on lamb meat production (Amer et al, 1999; Newton et al, 2017), and understanding factors that influence establishment of pregnancy in the ewe is key to improving flock reproductive performance
When considering the entire dataset, 11,026 operational taxonomic units (OTUs) were generated from 174 samples after quality control and removal of OTUs representing less than 10 sequences
The 11,026 OTUs were assigned to 32 phyla with Firmicutes, Proteobacteria, and Bacteroidetes being the three most abundant phyla representing 52, 16, and 11% of all reads, respectively (Supplementary Table 1)
Summary
Reproductive success is an important determinant of profitability for commercial sheep production enterprises focused on lamb meat production (Amer et al, 1999; Newton et al, 2017), and understanding factors that influence establishment of pregnancy in the ewe is key to improving flock reproductive performance. Numerous studies have shown the impact of factors such as age and nutrition on ewe reproductive performance (Gaskins et al, 2005; Pettigrew et al, 2019), there is a paucity of information regarding if and how the microbiota of the ewe reproductive tract may contribute to pregnancy outcome. Fluctuations within the host-associated microbial populations can explain specific phenotypes within a population. It is well known that the microbiota within the gastrointestinal tract of the ruminant is linked to several important aspects of host nutrition, metabolism, and health (Yeoman and White, 2014; Shabat et al, 2016; O’Hara et al, 2020). Other than knowledge about specific reproductive tract pathogens, comparatively little information is available about how the microbial communities as a whole, or specific members of the microbial communities within the vaginal tract, may influence aspects of reproduction in livestock
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