Associations among thermal biology, preovulatory follicle diameter, follicular and luteal vascularities, and sex steroid hormone concentrations during preovulatory and postovulatory periods in tropical beef cows

In Vivo Follicular and Uterine Arterial Indices as an Indicator of Successful Hormonal Stimulation for Inactive Ovaries in Repeat-Breeder Crossbred Dairy Cows Using a Short-Term Progesterone-Based Programme

“…The results of the present study support the hypothesis that the vascular index (coloured area) of ovary and UtA can be applied as an indicator of successful hormonal induction for ovarian dysfunction in repeat-breeder dairy cows. Although the information regarding the relationship between ovarian and uterine arterial indices and the resumption of follicular activity after hormonal stimulation in infertile dairy cows is scarce, the blood flow to the preovulatory follicle (POF) is markedly reduced in heat-stressed beef cows (vascularised area in pixels and %) with a synchronised ovulatory cycle [10] and heat-stressed dairy cows (Doppler index) with a spontaneous oestrous cycle [21]. Similar to normally cyclic dairy cattle [22], the vascularity (vascularised area in pixels) of POF and CL is a valuable predictor of pregnancy outcomes in fertile dairy cows.…”

“…For these responsive cattle, cows had greater follicular and UtA vascular indices on the day of the FTAI. Investigations in beef cows receiving CIDR in combination with GnRH, PGF, and equine chorionic gonadotropin have observed that, during the preovulatory period, POF vascularisation positively correlated with POF growth rates and vasodilator (oestradiol; E2) levels and tended to associate with POF growth rate in ovulating cows [10]. The blood flow of ovarian artery and middle UtA changed after the end of ovarian superstimulation in dairy cows that previously synchronised with CIDR and received follicle stimulating hormone [27].…”

“…To visualise the ovarian LF structure and UtA on the day of the FTAI (day 8), transrectal colour Doppler ultrasonography was performed by a single operator using a 7.5 MHz lineararray ultrasonic probe (HS-1600V; Honda Electronics, Toyohashi, Aichi, Japan) for B mode (grey scale) and Doppler functions (colour flow mapping and power Doppler functions). The amount of cross-sectional tissue areas of ovarian LF (LF ≤ 10.0 mm and LF > 10.0 mm) and UtA contralateral and ipsilateral to the LF ovary in which vascularisation was indicated as vascular areas, as well as being quantified from the Doppler colour sonogram images using the procedures described for beef cows [10] and mares [12]. Briefly, Doppler colour images per pixel density were created using Adobe Photoshop CC software (1990-2017, Adobe system).…”

“…As a non-invasive method, transrectal colour Doppler ultrasonography is considered to be an effective technique for the quantitative evaluation and clinical application of arterial blood flow not only in beef cows [8], but also in dairy cows [9]. Recently, our research group in the study of beef cows [10] and other research teams in the study of mares [11,12] and in dairy heifers [13] demonstrated that the reproductive vascular index, as indicated by the coloured area (pixels and %) of reproductive organ sections from the Doppler sonogram images, is able to indicate the blood supply of the female reproductive system. However, the investigation of vascularity of ovarian and uterine arteries after the hormonal treatment for inactive ovaries using the short-term P 4 -based programme has not yet been investigated in repeat-breeder crossbred dairy cows.…”

Effects of Heat Stress on Follicular Physiology in Dairy Cows

“…As expected, following the reduced size of the dominant HS follicle will influence the diameter of the pre-ovulatory follicle. The size of the pre-ovulatory follicle is reduced with a high environmental THI value [ 43 ]. In fact, the diameter of the pre-ovulatory follicle is reduced by an estimated 0.1 mm for each additional point on the THI value on the day of estrus [ 44 ].…”