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

SIMPLE SUMMARY: Blood supply of female reproductive organs plays an important role in reproductive performance in cattle. Ovarian and uterine arterial indices (vascularised area) from colour Doppler imaging provided important information about ovarian activity, supporting clinical diagnoses and reproductive management decisions in female cattle. However, the information regarding the relationship between reproductive vascular indices and resumption of follicular activity after hormonal stimulation for inactive ovaries in infertile dairy cows is scarce; thus, infertile crossbred dairy cows with inactive ovaries were induced using a 5-day progesterone-based programme. Our results highlighted that repeat-breeder crossbred dairy cows with greater follicular size and follicular and uterine arterial indices underwent a resumption of ovarian activity after hormonal stimulation. Therefore, additional information on follicular and uterine arterial indices that can be helpful in predicting the resumption of ovarian activity after hormonal stimulation in inactive ovary cows can be gained by reproductive vascularisation from colour Doppler ultrasonography. ABSTRACT: An investigation of vascularity of ovarian and uterine arteries after hormonal treatment for inactive ovaries using the short-term progesterone-based programme had not yet been explored in repeat-breeder crossbred dairy cows. To investigate the in vivo follicular and uterine arterial indices as an indicator of successful hormonal stimulation for inactive ovaries in repeat-breeder crossbred dairy cattle, 59 cows with inactive ovaries were induced with a 5-day progesterone-based protocol. At the completion of hormonal synchronisation, cows were divided into two groups according to the size of the largest follicle (LF) on their ovary: small (≤10.0 mm) and large (>10.0 mm) LFs. Vascularities of LF and uterine artery (UtA) were evaluated using a colour Doppler tool. Cows that presented with large LF had greater follicular and UtA vascular indices (p < 0.001) and pregnancy rate (p < 0.01) than cows bearing small LF on their ovary. There was a positive correlation (p < 0.001) between follicular size and LF and UtA vascular indices. Our findings highlighted that in vivo LF and UtA vascular indices at the completion of hormonal stimulation might be a promising indicator for predicting success in ovarian response to hormonal stimulation for inactive ovaries of infertile crossbred dairy cows.