Repeatability of preovulatory follicular diameter and uterine edema pattern in two consecutive cycles in the mare and how they are influenced by ovulation inductors

Abstract

Follicular diameter is used as a guiding tool to predict ovulation in the mare. However, the great range in preovulatory follicular diameter makes prediction of optimal breeding time based on follicular diameter unreliable. Uterine edema pattern is also useful to determine the best time to breed, since intensity of edema tends to dissipate as ovulation approaches, however, not every mare follows this pattern. The aims of this study were to assess the repeatability of preovulatory follicular diameter and uterine edema pattern in two consecutive spontaneous cycles and to determine how induction treatments (hCG, PGF(2)alpha and GnRH analogues) influence them. Fifty-three mares were followed during two consecutive cycles and scanned three times a day from 2 to 3 days before ovulation. During the first cycle, mares had a spontaneous ovulation and in the consecutive cycle mares received either: (a) no hormonal treatment; (b) 1500 IU hCG; (c) 125-250 microg Cloprostenol or (d) 2.1 mg Deslorelin implant. Mares ovulated consistently from similar follicular diameters in two consecutive spontaneous cycles (r=0.89; P<0.000). All three induction treatments had a significant effect on reducing the preovulatory follicular diameter (P<0.005). Mares showed fair correlation in uterine edema patterns in both consecutive non-induced cycles (r=0.71; P<0.005). In conclusion mares in consecutive cycles ovulated from consistent follicular diameters. Follicular diameters recorded from previous ovulations can be relied on to predict the optimal breeding time in successive cycles especially in mares that ovulate from unusually small follicles.

Effects of a single use of the GnRH analog buserelin on the induction of ovulation and endocrine profiles in heavy draft mares

“…The diameter of dominant follicles and uterine edema findings are considered effective indicators to predict ovulation timing in horses [3, 21, 28, 32]. The mean maximum diameter of the ovulatory follicle is usually between 40 and 45 mm, but there are variations depending on season and type of horse [32].…”

“…Uterine edema findings become most clear approximately 3 days before ovulation, but decrease 1 to 2 days before ovulation, thus uterine edema is considered an effective indicator for the timing of ovulation [3, 11]. However, uterine edema findings were found in 64% of anovulatory cycles during the breeding transition period [36], and significant uterine edema findings are also observed in endometritis [31].…”

The effect of mare's age on multiple ovulation rate, embryo recovery, post-transfer pregnancy rate, and interovulatory interval in a commercial embryo transfer program in Argentina

“…Mares with short intervals are usually found with a large follicle (>30 mm) at the time of flushing (time of PGF treatment), whereas mares with long IOI have small follicles at the time of flushing which may take 10-16 days to grow and ovulate or on fewer cases may have a large follicle which does not ovulate but regresses. It has been shown that there is a good degree of individual repeatability in the preovulatory follicular diameter (Cuervo-Arango and Newcombe, 2008) and in the length of the IOI within consecutive cycles of individual mares (reviewed by Ginther, 1992). …”

Equine Infectious Endometritis—Clinical and Subclinical Cases

“…Christoffersen et al [31] showed that mares susceptible to endometritis had a prolonged endometrial gene expression of proinflammatory cytokines compared with resistant mares in response to experimentally induced endometritis. It can be difficult to compare edema patterns between mares because of differences in estrogen profiles; however Cuervo-Arango and Newcombe [39] investigated the repeatability of the endometrial edema pattern in two consecutive cycles in mares. They found a fair correlation (Spearman rank correlation, r ¼ 0.71) of the endometrial edema pattern between the cycles.…”