The transfer of parthenogenetic embryos following artificial insemination in cows can enhance pregnancy recognition via the secretion of interferon tau.

Repeat breeding is a reproductive disorder in cattle. Embryo transfer following artificial insemination (AI) improves pregnancy rate by replenishing interferon tau (IFNT), but it results in a notably higher rate of twin occurrence. This study hypothesized that parthenogenetic (PA) embryo transfer following AI (AI + PA) could improve the conception rate because that PA embryo become as a supplemental source of IFNT without twins. PA embryos showed higher IFNT mRNA expression than in vitro fertilization (IVF) embryos. An examination of the effect of the cultured conditioned media (CM) of PA or IVF embryos on Madin-Darby bovine kidney cells with stably introduced promoter-reporter constructs of interferon-stimulated gene 15 (ISG15, marker of IFN response) showed higher stimulation levels of ISG15 promoter activity with PA than with IVF embryo. We investigated in vivo the effect of AI + PA on healthy Japanese Black cattle. Cattle transferred with PA embryo alone were non-fertile, but those that underwent AI + PA showed a pregnancy rate of 53.3%, the similar as that with AI alone (60%). In pregnant cattle in AI + PA group, adding the PA embryo upregulated the expression of ISGs and plasma progesterone concentration. No twin were generated in AI only and AI + PA groups. Using repeat breeding Holstein cows that did not become pregnant with 4-9 times of AI, transfer of PA embryo following AI resulted in a higher pregnancy rate than that of control (AI only). We suggest that AI + PA may be beneficial for improving maternal pregnancy recognition in repeat breeder cattle while avoiding twin generation.

Improvement of fertility in repeat breeder dairy cattle by embryo transfer following artificial insemination: possibility of interferon tau replenishment effect.

Repeat breeder cattle do not become pregnant until after three or more breeding attempts; this represents a critical reproductive disorder. Embryo transfer (ET) following artificial insemination (AI) in repeat breeder cattle reportedly improves pregnancy rate, leading to speculation that interferon tau (IFNT) is associated with this phenomenon. However, the reason why the conception rate improves remains unknown. We investigated the effect of ET following AI on repeat breeder cattle in field tests, and determined whether adding an embryo affects the maternal immune cells detected by interferon-stimulated genes (ISGs), marker genes of IFN response. In total, 1122 repeat breeder cattle were implanted with in vitro fertilization (IVF) embryos after previous AI. ET following AI resulted in pregnancy rates of 46.9% in repeat breeder dairy cattle. In basic in vivo tests, to investigate the effect of adding embryos, ISGs mRNA expression levels were significantly higher in the AI + ET group than in the AI + sham group (transfer of only embryonic cryopreservation solution). Then, we examined the effect of cultured conditioned media (CM) of IVF embryos on splenic immune cells and Madin-Darby bovine kidney (MDBK) cells with stably introduced ISG15 promoter-reporter constructs. These cells exhibited a specific increase in ISG15 mRNA expression and promoter activity when treated with the CM of IVF embryos, suggesting that IVF embryos have the potential to produce and release IFNT. In conclusion, ET following AI is beneficial for improving conception in repeat breeder cattle. Added embryos may produce and secrete IFNT, resulting in the increased expression of ISGs.