Reproductive biomarkers of cows - current state of research and prospects (review)

Production of in vitro embryos (IVP-embryos) using oocytes retrieved by aspiration of ovarian follicles (OPU) is today a traditional practice in cattle breeding (R.Yu. Chinarov et al., 2023; L.B. Ferré et al., 2023). Despite the significant progress made in this area, the challenge is to increase the number of transferable embryos produced per OPU session, as this directly affects the efficiency of embryo transfer programs. Considering the direct impact of reproductive hormones in the regulation of reproductive functions of females, their contents in the blood is considered as potential predictors of the efficiency of OPU/IVP technology (R.Yu. Chinarov, 2024). The aim of this review is to analyze the current state and research results of the associations between blood content of reproductive hormones of different classes and the efficiency of assisted reproductive technologies to identify potential predictors for improvement of OPU/IVP technology in cattle. Studies conducted on various breeds of European (Bos taurus) and zebu (Bos indicus) cattle have revealed associations between the content of progesterone, estradiol-17β, follicle-stimulating hormone (FSH) and Anti-Mullerian hormone (AMH) in follicular fluid and/or in blood with the efficiency of OPU. Higher concentrations of progesterone in the blood serum of Sahiwal cows were associated with a higher number of follicles suitable for aspiration (nF), the total number of retrieved oocyte-cumulus complexes (OCCs) and the number of viable OCCs (M. Nawaz et al., 2022). Bos taurus × Bos indicus crossbreeds with average progesterone concentrations in blood serum were characterized by a higher blastocyst rate (%BL) (L.F.M. Pfeifer et al., 2009). Higher concentrations of estradiol-17β in the follicular fluid were associated with higher nF values in crossbred beef heifers (F. Mossa et al., 2010) and non-pregnant Holstein cows (K. Sakaguchi et al., 2019), as well as with a higher %BL value in donor heifers of the Holstein breed (N. Araki et al., 1998). Higher values of the %BL indices were achieved in donor heifers of the Istobian breed, which have higher values of the ratio of the concentration of estradiol-17b in blood serum to the number of OCCs (R.Yu. Chinarov et al., 2025). Negative correlations of FSH concentration in blood serum or blood plasma with n F values were observed in heifers and non-pregnant Holstein cows (J.M. Haughian et al., 2004; K. Sakaguchi et al., 2019), in non-lactating dairy cows (F. Mossa et al., 2010), in heifers and lactating cows of beef cattle (J.J. Ireland et al., 2007; J. Singh et al., 2004). Higher concentrations of AMH were associated with higher nF values in donors of the Holstein breed (B.M. Guerreiro et al., 2014; A. Vernunft et al., 2015), in high-productive dairy cows (A.H. Souza et al., 2015), lactating cows of the Tagil breed (R.Yu. Chinarov et al., 2024), Hanwoo beef cattle (N. Ghanem et al., 2016), Japanese black cattle (H. Hirayama et al., 2019), and Nelore zebu cattle (B.M. Guerreiro et al., 2014). Thus, the results of the analysis showed the presence of a number of associations of reproductive hormones with the efficiency of assisted reproductive technologies in different cattle breeds. In this regard, monitoring the concentrations of reproductive hormones in the blood serum of females can be a useful tool for selecting donors for OPU and predicting the efficiency of production of IVP-embryos in cattle. It is advisable to conduct further studies of the associations of reproductive hormones with the efficiency of OPU/IVP in different cattle breeds, considering the age and physiological status of donors, as well as the technological regimens of their use.