Merino ewe lambing after stimulation with prostaglandin and PMSG and insemination with sperm of grey Karakul rambs

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Aim. To determine the effectiveness of a two-time treatment with prostaglandin F-2α (PGF2α) followed by the injection of pregnant mare serum gonadotropin (PMSG) for stimulation of sexual activity in sheep in the second half of the estrous season in the scheme of increasing the lambing rate. Methods. Thirty-seven 2.5-yearold ewes of the Askanian Merino breed, which were kept together from the age of one year, were used. In September 2018, 28 animals of this group lambed and had sucklings until November 20. Hormonal stimulation was started on December 7, 2018 by injecting all ewes with 1 ml of synthetic PGF2α and 1 ml of Prozerin. The second injection of PGF2α was given 10 days after the fi rst one. Simultaneously with the second treatment with PGF2α, the animals were injected with 500 IE of PMSG (Sergon, Czech Republic) and 2.5 ml of SuperAminoC (South Korea). The presence of estrus was not detected, and the ewes were forcibly inseminated with freshly obtained sperm of 4 grey rams of the Askanian Karakul breed in the morning for three days, beginning with the fi rst day after the PMSG injection. During the fi rst treatment with PGF2α and 3 days before the second one, the genitals of 12 ewes were sonographically examined. Results. In total, 45.9 % of stimulated animals lambed; the total fecundity was 75.7 %, and the average prolifi cacy – 1.65 ± 0.18 lambs per ewe. Among the animals, which before the experiment had the sucklings, 57.1 % lambed, among those, who did not have the suckling, – 11.1 %. After using the sperm of ram 17314, 77.8 % of ewes lambed, for rams 73697, 73792 and 73796 – 30.0, 44.4 and 33.3 %, respectively. Among the 19 lambs analyzed by wool color, 10 lambs were completely black, 9 were black with white spots. Among the spotted lambs, the color on the back, forearms and hips of one lamb had an additional shade, close to gray. Ultrasound testing showed that the ewes, which before the experiment had sucklings, showed better genital reactivity. According to the distribution of lambs by wool color, an assumption about possible partial incompatibility of the genotypes of Askanian Merino ewes and grey Karakul sheep was made that requires further study. Conclusions. The scheme of stimulating sexual activity based on two-time treatment with PGF2α followed by an injection of PMSG is capable of ensuring lambing of more than 70 % of stimulated sheep with the prolifi cacy of 1.65 lambs per ewe. A factor, increasing the effectiveness of the scheme, is the presence of sucking lambs of ewes before the stimulation starts.