Infertility in lactating dairy cows is explained partially by the metabolic state associated with high milk production. The hypothesis was that lactating and nonlactating cows would differ in endometrial and placental transcriptomes during early pregnancy (day 28 to 42) and this difference would explain the predisposition for lactating cows to have embryonic loss at that time. Cows were either milked or not milked after calving. Reproductive [endometrium (caruncular and intercaruncular) and placenta] and liver tissues were collected on day 28, 35, and 42 of pregnancy. The hypothesis was rejected because no effect of lactation on mRNA abundance within reproductive tissues was found. Large differences within liver demonstrated the utility of the model to test an effect of lactation on tissue gene expression. Major changes in gene expression in reproductive tissues across time were found. Greater activation of the transcriptome for the recruitment and activation of macrophages was found in the endometrium and placenta. Changes in glucose metabolism between day 28 and 42 included greater mRNA abundance of rate-limiting genes for gluconeogenesis in intercaruncular endometrium and evidence for the establishment of aerobic glycolysis (Warburg effect) in the placenta. Temporal changes were predicted to be controlled by CSF1, PDGFB, TGFB1, and JUN. Production of nitric oxide and reactive oxygen species bymacrophages was identified as amechanism to promote angiogenesis in the endometrium. Reported differences in pregnancy development for lactating vs. nonlactating cows could be explained by systemic glucose availability to the conceptus and appeared to be independent of the endometrial and placental transcriptomes.
Expression of genes in the pregnant bovine uterus is not affected by lactation.