Influence of hormonal synchronization protocols in heifers-recipients on their pregnancy rate with the use of frozen-thawed embryos

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At the moment, there are a great number of protocols enabling to prepare recipients for embryo transfer. However, because of their effectiveness variety on cattle breeding farms the issue of searching of practical schemes that allow successful reproductive cycle synchronization in recipients with the achievement of their highest pregnancy rate becomes relevant. Based on the information above, the aim of the study was to determine the most effective estrous cycle synchronization protocol in recipient heifers before embryo transfer which provide the high level of their pregnancy rate with the use of frozen-thawed embryos. The research was carried out on the beef cattle in Samara region of Russia. In the course of the study, the heifers (n=107) were selected as the potential recipients and then divided into three groups depending on the applied protocol for the estrous cycle synchronization. All the recipients were transferred with frozen-thawed embryos obtained in vivo from Aberdeen Angus donor cows. The doses of the drug products indicated below were administrated per one animal. During the study, it was found that in group I where we used a protocol included a double administration of 2 ml of the drug "Oestrophan" (Czech Republic) with an interval of 11 days estrous cycles were synchronized in 72.73±0.80 percent of animals. The pregnancy rate in group I was 29.17±0.97 percent. In group II where we applied a protocol included a double administration of "Surfagon" (Russia) at a dose of 10 ml and Oestrophan with an interval of 11 days estrous cycles were synchronized in 50.0±0.86 percent of animals. The pregnancy rate in that group was 61.11±1.22 percent. In group III that included the application of intravaginal progesterone implant CIDR with a simultaneous administration of Surfagon at a dose of 2 ml and at the time of CIDR extraction the administration of 2 ml of Oestrophan, estrous cycles were synchronized in 63.16±0.80 percent of animals. The pregnancy rate in that group was 66.67±1.00 percent. Thus, the group III was characterized by the highest pregnancy rate that was achieved by the application of the protocol included intravaginal progesterone implant CIDR in combination with both medical products Surfagon and Oestrophan.