Monitoring of health status, performance and transcript abundance of some genes in dairy heifers produced by embryo transfer or artificial insemination.

The use of multiple ovulation and embryo transfer (MOET) technology in the dairy cattle industry has increased dramatically in recent decades for the production of offspring from genetically superior cows. Yet, its long-term ramifications on adult performance haven't been adequately clarified. Therefore, this study targeted comparing dairy heifers born after the transfer of in vivo-produced embryos (MOET-heifers, n=400) and those born after artificial insemination (AI-heifers, n=340). The performance of MOET-heifers and AI-heifers was compared from birth till completion of the first lactation regarding health, fertility and some lactational performance parameters. The transcript abundance of several genes was also assessed in peripheral blood leukocytes (PBWC). Results showed greater pre-weaning mortalities, greater likelihood of being culled as a nulliparous heifer and younger age at first insemination in AI-heifers (P<0.001). At their first calving, primiparous MOET-heifers experienced a greater (P<0.01) incidence of stillbirth compared to primiparous AI-heifers. In spite of that, primiparous AI-heifers were more likely to be culled due to infertility (P<0.001), took a greater number of inseminations to achieve pregnancy (P<0.01) and displayed a longer first calving interval. There was a similar lactational performance between the two groups. Upregulation of the transcript levels of TAC3, LOC522763, TFF2, SAXO2, CNKSR3, and ALAS2 was interestingly observed in primiparous MOET-heifers, compared to primiparous AI-heifers. In conclusion, MOET-heifers were less likely to be culled during the first year of life, had superior reproductive performance versus AI-heifers during their first lactation and expressed upregulation of genes associated with fertility.