ParityPropylene glycol a b s t r a c t This work was conducted as a first time commercial production of embryos from lactating Holstein and Brown Swiss cows using multiple ovulation embryo transfer (MOET) technology in Egypt. We studied factors affecting the superovulatory response (SR) in superovulated cows and effects of propylene glycol (PG) on embryo quality. Daily milk production at flushing had significantly negative effects on SR and embryo yields in superovulated cows. In addition, Brown Swiss cows had better SR than Holstein cows.Moreover, cows having more than 3 parities yielded better response, compared to cows in the first three parities. However, factors such as body weight at flushing, body condition score (BCS) at flushing and days in milk (DIM) at flushing did not have any association with SR in cows. In addition, drenching of PG prior to and during the superovulatory treatment improved SR (Right CL number, P < 0.05; Left CL number, P < 0.05), total embryos per flush (P < 0.05), first grade embryos per flush (P < 0.01) and tended to improve transferable embryos (P ¼ 0.13) and second grade embryos per flush (P ¼ 0.11). However, it tended to increase the number of degenerated embryos per flush (0.06). In conclusion, commercial production of embryos from lactating Holstein and Brown Swiss cows regardless of stage of estrous cycle by MOET proved successful under Egyptian conditions. Milk yield was negatively associated with SR and embryo yields in superovulated cows. Moreover, drenching of PG prior to and during the superovulatory treatment improved SR and embryo yields.

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 have not 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 < .001). At their first calving, primiparous MOET‐heifers experienced a greater (p < .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 < .001), took a greater number of inseminations to achieve pregnancy (p < .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.

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Global warming is an international alarming phenomenon that affects all aspects of life including animal biology. Environmental heat stress is associated with compromised reproductive performance in mammals, particularly animals under stressful conditions (De Rensis et al., 2021). Temperature-humidity index (THI) is the most important indicator of the degree of heat stress to which dairy animals are exposed (Ratchamak et al., 2021) as it combines effects of both ambient temperature and relative humidity. Heat-stressed cows show poor reproductive performance and achieve lower conception rates when compared to non-stressed herd-mates, particularly when inseminated using sexed semen (Oikawa et al., 2019). Despite the modern cooling technologies and its favourable consequences on conception rates during hot summer months, embryo transfer (ET) is still representing the most effective strategy to overcome the negative impacts of heat