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The present study investigated the effect of superstimulation to improve in vitro embryo production in the Gulf area, where the temperature is high. Holstein cows were classified into the control and superstimulation groups. Superstimulation was induced with a single intramuscular injection of pregnant mare serum gonadotropin (PMSG; 2500 IU) on day 14 of the estrus cycle (day 0; estrus). The development of follicles was evaluated by ultrasonography of the ovaries daily. At 40 h after the PMSG injection, oocytes were collected by the ovum pick-up (OPU) technique. OPU was performed at the same stage of the estrus cycle in the control group as in the superstimulation group. The number of follicles with a diameter of more than 6 mm and the number of retrieved cumulus-oocyte complexes were significantly higher in the superstimulation group than in the control group. Furthermore, the maturation rate was higher in the superstimulation group than in the control group. Cloned embryos were produced by somatic cell nuclear transfer using matured oocytes. The cleavage and blastocyst formation rates were significantly higher in the superstimulation group than in the control group. In conclusion, a single injection of PMSG can facilitate the efficient production of cloned cow embryos.

Despite the tremendous advancement in somatic cell nuclear transfer (SCNT) in camels, the generation of cloned calf using SCNT in cows is yet to be reported in the United Arab Emirates (UAE). The present study intended to produce cloned calves in the local environment of the UAE. We surgically collected ear tissue from two high-performance Holstein cows (average production of 71 liter/day) and established the fibroblast cell line to perform SCNT. Fifty-seven (18.48%) blastocysts were derived from 330 fused oocytes for cell donor A, and 51 (19.14%) blastocysts were generated from 289 fused oocytes for cell donor B. We used 102 recipients for embryo transfer; among those, 53 and 49 recipients received embryos reconstructed with cell donor A and B, respectively. A single blastocyst in transfer media was transferred deep into the horn of the uterus of natural cycling recipient cows by trans cervical method on Day 7; where estrus was considered as Day 0. Non-return to estrus (up to 42 days), early pregnancy, and the live birth rate did not differ significantly for the two donor cells. Four (26.67%) and 1 (7.69%) live calves were produced for cell donor A and B, respectively. Microsatellite analysis of 18 bovine-specific loci confirmed the perfect match of cell donors and cloned calves. This is the first reported case of cloned calves using SCNT in the UAE. Our results could benefit the UAE dairy industry by supporting the locally produced high-performance replacement heifers. [ABSTRACT FROM AUTHOR]