Profile of steroid hormones during oestrus and early pregnancy in Arabian mares

Faecal and plasma steroid evaluations are well established approaches for monitoring reproductive function in mares. The purpose of this study was to detect the ovarian and uterine changes by transrectal ultrasonographic scanning, beside the estimation of gestagen and estradiol-1713 profiles in plasma and faecal samples of Arabian mares. Eight cyclic barren mares of different parities were used in the current work, and hormones were assayed using radioimmunoassay. The follicular growth was accompanied by a significant (P<0.05) decrease and increase in the profile of plasma progesterone (P4) and estradiol-1 713 (E 1 -176), respectively. In addition, the minimum level of P4, and the maximum level of El -1713 were detected at day 0 of ovulation. Similarly, the faecal progesterone metabolites (20oc-hydroxy-progesterone; i.e. 20oc-G) content showed a significant (P<0.05) decrease in its value starting from day -7 reaching its minimum level at second day post ovulation, meanwhile, the faecal El -1713 content was reaching its maximum value on day 1 after ovulation. Following ovulation, the plasma P4 and faecal 20oc-G content showed a continuous significant (P<0.05) increase starting from the 3rd day post ovulation, and the levels of both faecal and plasma El-17B showed a continuous significant decrease. The levels of P4 in plasma and 20-G in faeces increased significantly (P<0.05) at day 14 to day 45 of gestation than those recorded at day 0 in nonpregnant mares. Moreover, the levels of El -1713 in plasma and faeces increased significantly (P<0.05) at days 21 up to 45 of gestation than those estimated during 14th day of gestation as well as in nonpregnant mares. In conclusion, both ultrasonography and analysis of P4 and El -1713 in plasma, and 20cx-G and El -1713 in faeces have a predictive value for assessment of the follicular sizes, ovulation time and early pregnancy in Arabian mares.