Evaluation of the factors that affect the pregnancy rates during embryo transfer in beef heifers

Abstract

The aim of this study was to evaluate the effects of the transfer side, transfer location, cervix transfer score, type and diameter of corpus luteum (CL) during embryo transfer on pregnancy rates in beef heifers. Progesterone‐based synchronization and superovulation protocol were applied to Simmental cows used as donors (n = 168). Uterine flushings were performed on day 7 following artificial insemination. Obtained Code I (excellent or good) and II (fair) quality embryos were transferred to recipient beef heifers (n = 561). During embryo transfer, side of transfer (right or left), transfer location (the cranial or middle third of uterine horn), cervix transfer score (easy, moderate or difficult) and type (CLa, CLb and CLc) and diameter of CL were determined. Pregnancy rates following the transfer of Code I and II embryos were 44.66% and 33.07%, respectively (p < .05). The rates of pregnancy after transfers to the right and left uterine horn were 37% and 42.2%, respectively (p > .05). The pregnancy rates were 41.2%, 34.9% and 30.3% for cervix transfer scores as easy, moderate and difficult, respectively (p > .05). Pregnancy rates after transfer to the cranial third and middle third were 41.06% and 29.67%, respectively (p < .05). According to types of CL, pregnancy rates were 31.7%, 40.4% and 45.3% for CLa, CLb and CLc, respectively (p < .05). Moreover, it was found that as the CL diameter increased, the pregnancy rates increased. As a result, it was concluded that there was no effect of side of transfer and cervix transfer score, but embryo quality, transfer location, type and diameter of CL had significant effects on the pregnancy rate during embryo transfer in beef heifers.

The incompletely fulfilled promise of embryo transfer in cattle—why aren’t pregnancy rates greater and what can we do about it?

“…That one or more of insults to the reproductive tract are potentially deleterious to pregnancy establishment is indicated by observations that the difficulty in passing the cervix and depositing the embryo in the uterus is negatively associated with P/ET ( Jaśkowski et al, 2010 ; Kasimanickam et al, 2018 , 2019 ; Alkan et al, 2020 ). Moreover, the physical characteristics of the transfer instrument have been reported to affect pregnancy success.…”

Factors Affecting Pregnancy Rate Per Embryo Transfer of In Vivo Produced Embryos in Recipient Holstein Heifers

“…Nevertheless, other research papers reported that increase in the concentration of P4 in accordance with the corpus luteum increase in crossbred recipients and according to Binelli et al, (2001), larger corpus luteum in recipients may increase pregnancy rates in embryo transfer programs. On the other hand, Alkan et al, (2020) reported that cavity-containing corpora lutea resulted in higher pregnancy rates in heifers receiving fresh in vivo produced embryos. In addition, that, Szelenyi et al, (2019) found that pregnancy losses in Holstein-Friesian cows examined by ultrasonography between days 29-42 after insemination were higher among cows with cavity-containing corpora lutea The present investigation cleared that PR/ET was significantly higher in embryo recipient Holstein heifers in which estrus or heat was induced using PGF2 alpha, as compared to recipient heifers with spontaneous heat.…”

“…Embryo transfer technology is an important breeding technique which aids in fortification of genetic superiority of cattle herds for both improved production and reproduction with potential improvement of farm economics (Dochi, 2019;Alkan et al, 2020). Multiple studies have been conducted to elucidate factors affecting pregnancy establishment in embryo recipient heifers and cows after transfer of in vivo or in vitro produced embryos (Block et al, 2009).…”

“…Embryo quality grade was demonstrated to have significant effects on pregnancy rates (Van Soom et al, 2001;Stroud and Hasler, 2006). Embryos of the highest grade were associated with significantly higher pregnancy rates than embryos of lower grades (Stringfellow, 2010;Alkan et al, 2020). According to the study conducted by Alkan et Theriogenology al., (2020), code 1 embryo (excellent or good) resulted in higher (P<0.05) pregnancy rates, when compared to code 2 embryo (Fair) after transfer into recipient beef heifers.…”

“…Cavities of corpus luteum are found in 40-80% of the estrous cycles of cows and heifers treated with progesterone or prostaglandin, and progesterone concentrations are not influenced by the presence of the cavity (Spell et al, 2001;Marques et al, 2002). However, the use of corpus luteum with cavity has generated controversy (Grygar et al, 1997;Marques et al, 2002;Looney et al, 2006 andSiqueira et al, 2009;Alkan et al, 2020). Pregnancy rate in embryo recipient cows was not affected by the type of corpus luteum (compact versus cavitory) or circulating progesterone concentrations (Nogueira et al, 2012).…”