Physiological and Endocrinological Characterization of Mid-Cycle Oestrus in Crossbred Cows

Abstract

To study the follicular, luteal and endocrinological turnover during Mid-cycle oestrus (MCO) in comparison with true oestrus (OES) in crossbred cattle. A total of 36 animals were categorized into two groups viz. OES (n = 18) and MCO (n = 18). The diameter of the dominant follicle (DF) and corpus luteum and peri-follicular blood flow parameters were documented ultrasonographically on the day of OES and MCO. Plasma progesterone and oestradiol concentrations were analysed on day 9 of OES group and on the day of MCO. There was no significant difference in the diameter of DF between OES and MCO, but the diameter of CL was significantly larger in MCO than in OES. The values of Doppler pulse duration and pulsatility index of peri-follicular blood flow were significantly higher in MCO than OES, which was indicative of an ovulatory status of DF in MCO. In MCO, the oestradiol secreted by the DF over rode the low progesterone and induced the animal to exhibit oestrus-like signs during the mid luteal phase of the cycle.