Abstract
The purpose of our work was to determine the effectiveness of using of dairy cows as recipients for obtaining twin calves of the meat direction of produc-tivity. The study was conducted in LLC "Agricultural enterprise" Nikolaevskoe", Lugovets village, Mglinsky district. For the experiment cows and first-calf heifers (n=50) were selected and divided into three groups according to the breed princi-ple. In group I (n=22) Swiss breed animals were selected, in group II (n=13) - black-and-white cows, in group III (n=15) - crossbred cattle. All animals selected for the experiment were previously subjected to hormonal stimulation in order to synchronize the sexual cycles. The synchronization scheme included the injection of GnRh analogues at a dose of 10 ml IM and PgF2a cloprostenol at a dose of 500 mg per animal. With the manifestation of symptoms of estrus, all animals were arti-ficially inseminated with the sexed semen of a Belgian blue bull. On the seventh day of the sexual cycle, all inseminated animals had the procedure of replanting a frozen-thawed embryo into the contralateral uterine horn relative to the corpus lu-teum diagnosed on the ovary. To avoid freemartinism of heifers, the recipients were implanted with sexed embryos which were previously obtained from donor cows of the Hereford breed. During the study, it was found that the recipients in groups I, II and III had twins in 45.46% (10/22), 15.39% (2/13) and 20.0% (3/15) cases of joint application of biotechnological methods. The birth of one transplant calf was recorded in group I in 18.18% (4/22) of cows, in group II - 23.08% (3/13) and in group III - 33.33% (5/15) respectively. The birth of one calf obtained from artificial insemination was noted in group I in 31.82% (7/22) of animals, in group II - 38.46% (5/13) and in group III - 40.0% (6/15) respectively. The rest of the cows had no calves. Thus, it was found that the percentage of twins in the progeny was significantly higher (P?0.01) in group I compared with groups II and III. In groups I, II and III the total yield of calves was 140.92% (31/22), 92.32% (12/13) and 113.33% (17/15), respectively.
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