MICROBE · Metagenomic Investigation of Cow Reproductive Biology and Ecology

Metagenomic Investigation of Cow Reproductive Biology and Ecology

Ireland has the fastest growing dairy industry in the EU and is expected to produce 41% more milk in 2026 compared with 2016. Dairy cows with poor fertility cows pose a substantial challenge to achieving this target. Milk production in Ireland is seasonal due to changes in pasture growth throughout the year. Cows calve in February and March; lactate until December when they are “dried off”; and are non-lactating until the birth of a new calf initiates a new lactation cycle. Reproductive performance is evaluated as the proportion of the herd that calves in the first six weeks of the calving season. The current average of 65% in dairy herds is considerably below the target of 90%. This means 35% of cows produce milk for only 230 to 270 days each year instead of the optimum 305 days. Endometritis is an inflammatory disease of the endometrium lining the uterus, and is a leading cause of failed pregnancy establishment. The disease affects ~30% of cows, increases embryo mortality by 25%, and costs the EU and USA dairy industries €2 billion annually. The endometrium and microbiota (population of microbes) are usually in a state of symbiosis when the cow is either receptive to pregnancy or pregnant. This symbiosis is disrupted (dysbiosis) at calving when pathogens such as Fusobacterium necrophorum and Trueperella pyogenes populate the uterus and produce inflammatory, pore-forming toxins or virulence factors that damage the endometrium. This may explain why endometritis has long term negative effects on embryo survival, but the mechanisms of how endometrium-microbe interactions affect embryo survival are unknown. Presently, mechanisms linking the uterine microbiota to embryo survival have not been elucidated. Cows offer many advantages as an animal model to study the function of the uterine microbiota: bovine uterine biology and pregnancy development are well characterized; and the uterus is relatively accessible through non-invasive sampling. The objectives of this project were to (1) examine endometrium-bacteria interactions at the level of the transcriptome and metagenome, and test the hypothesis that such interactions are responsive to genomic selection for fertility; (2) isolate and culture specific uterine microbes from two genotypes of dairy cows divergent in fertility; and (3) use ex-vivo tissue culture systems to validate novel functional mechanisms by which uterine bacteria isolated from cows divergent in genetic merit for fertility interact with the oviduct and endometrium during sperm transport and embryo development.

Data: CORDIS, © European Union