Abstract
To date, there is a lack of research into the vaginal and sperm microbiome and its bearing on artificial insemination (AI) success in the ovine species. Using hypervariable regions V3–V4 of the 16S rRNA, we describe, for the first time, the combined effect of the ovine microbiome of both females (50 ewes belonging to five herds) and males (five AI rams from an AI center) on AI outcome. Differences in microbiota abundance between pregnant and non-pregnant ewes and between ewes carrying progesterone-releasing intravaginal devices (PRID) with or without antibiotic were tested at different taxonomic levels. The antibiotic treatment applied with the PRID only altered Streptobacillus genus abundance, which was significantly lower in ewes carrying PRID with antibiotic. Mageebacillus, Histophilus, Actinobacilllus and Sneathia genera were significantly less abundant in pregnant ewes. In addition, these genera were more abundant in two farms with higher AI failure. Species of these genera such as Actinobacillus seminis and Histophilus somni have been associated with reproductive disorders in the ovine species. These genera were not present in the sperm samples of AI rams, but were found in the foreskin samples of rams belonging to herd 2 (with high AI failure rate) indicating that their presence in ewes’ vagina could be due to prior transmission by natural mating with rams reared in the herd.
Highlights
Artificial insemination (AI) is a reproductive technique playing an important role in genetic breeding programs of milk ruminants as it: (i) enables progeny tests to predict rams genetic breeding values (EBVs) according to their daughters’ performances; (ii) contributes to connect herds, which is necessary to establish a common genetic basis to compare EBVs among animals of the whole population and (iii) enables dissemination of the genetic improvement achieved by the genetic program to the whole population, using genetically elite rams
We have performed this study using intravaginal devices and conventional sperm straws because our main aim was to detect the microbiota associated to artificial insemination (AI) failure, and AIs in commercial dairy ewes are always performed in this way
We can affirm that microbiota composition of the ewe’s genital tract is primarily responsible for AI success/failure, whereas sperm microbiota of AI rams did not show any relationship with AI outcome
Summary
Artificial insemination (AI) is a reproductive technique playing an important role in genetic breeding programs of milk ruminants as it: (i) enables progeny tests to predict rams genetic breeding values (EBVs) according to their daughters’ performances; (ii) contributes to connect herds, which is necessary to establish a common genetic basis to compare EBVs among animals of the whole population and (iii) enables dissemination of the genetic improvement achieved by the genetic program to the whole population, using genetically elite rams. Low AI efficiency has a negative economic impact on dairy sheep breeding programs for two main reasons; firstly, it extends the generational interval, delaying genetic enhancement and, secondly, it increases the number of rams to be tested to ensure sufficient progeny Many known factors, such as ewes’ cervix conformation, the need to use fresh semen to perform cervical inseminations and the lack of knowledge regarding the exact stage of the ewe’s ovulatory cycle at AI, all contribute to variable extents to lowering AI success rates in this species. Massive genome sequencing technologies can reveal bacterial composition based on the same 16S rRNA gene sequencing, targeting certain hypervariable regions within the gene These serve as a molecular fingerprint at the genus and species level [4,5] and are interesting for non-culturable species and those present in low abundance
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