Search

Luteolysis is a key event in cattle reproduction. A standard dose of exogenous PGF(2α) will induce full luteolysis in the majority of cows with a matured corpus luteum (CL). However, this will not occur in cows with a CL

Early embryonic loss (EEL) negatively affects the reproductive efficiency of equine reproduction. A sign of future EEL is when the embryo proper (EP) fails to develop within the embryonic vesicle after 30 days of gestation. The earlier the identification of impending EEL, the earlier the mare can be rebred to allow a second chance of pregnancy. The objectives of this study were to determine the percentage of embryonic vesicles with a visible EP at 18-28 days of gestation and to study the association between the presence/absence of the EP at different days of gestation and the future viability of the pregnancy. A total of 1,256 pregnancies were identified and followed by transrectal B-mode ultrasonography 12-45 days post ovulation in mares of the same Thoroughbred farm. The identification of the EP was attempted once during days 18-28. Pregnancy reconfirmation was performed on days 35-45. The percentage of vesicles with an EP increased gradually from days 18 (2.8%) to 21 (86.9%) (P 71%) on day 20 of gestation. The lack of a positive identification of an EP from day 20 onward is associated with a higher EEL rate.

https://www.sciencedirect.com/journal/theriogenology Este es el pre-print que se ha publicado de forma definitiva en https://doi.org/10.1016/j.theriogenology.2011.07.006 Preprint

The association between use of hormone treatments to induce estrus and ovulation and the incidence of hemorrhagic anovulatory follicles (HAFs) was studied in a mixed population of mares (Equus caballus) during two breeding seasons in a commercial breeding clinic. Mares treated with cloprostenol (CLO) were more likely to develop HAFs than were mares with spontaneous cycles (P0.001) or those treated with human chorionic gonadotropin alone (P=0.08). There was no significant effect of season on the incidence of HAFs. The mean (+/-SEM) interval from CLO treatment to beginning of HAF development was 6.1+/-0.5 d. Age of mares with HAF cycles was not different (12+/-1.3 yr; P0.05) from that of mares with ovulatory cycles (10.5+/-1.5 yr).

Reproductive records of the entire lives of two mares with abnormally high incidence of multiple ovulation and hemorrhagic anovulatory follicles were analyzed retrospectively. Chi-square analysis was used to test statistically the effect of cloprostenol, a prostaglandin F2 analog, on the incidence of multiple ovulations, hemorrhagic anovulatory follicles, and its ultrasonographic appearance. A total of 319 estrous cycles during a 17-year period were analyzed. Cycles induced with cloprostenol were more likely ( P

Although the ovulatory effects of prostaglandins are well documented in several domestic species including horses, there has been little attention paid to the use of this ovulatory effect for clinical purposes. Mares often grow large follicles during the luteal phase that may or may not ovulate before progesterone levels decline. Clinical observations of administering prostaglandins in disestrous mares with large follicles suggest that there may be a negative correlation between follicular diameter and interval from treatment to ovulation. The objectives of this study were twofold: to investigate the cloprostenol dose rate effect on interval to ovulation and to confirm the negative correlation between follicular diameter and interval to ovulation. The hypothesis tested was that high doses of cloprostenol given in diestrous to mares with larger follicles would induce ovulation more rapidly than in mares given lower doses or with smaller follicles. To test the hypothesis, a total of 1,234 estrous cycles were induced with different doses of cloprostenol (ranging from 8.75 to 625 mu g). All mares had at least one follicle of 28 mm or larger. Dominant follicles were followed by transrectal ultrasound examinations every other day until ovulation was detected. There was a significant effect of dose (P < .000) and follicular diameter (P < .000) on the interval from treatment to ovulation. The shortest mean interval (2.4 days) was observed after administration of 625 mu g in mares with follicles 36mm or larger, whereas the longest (4.9 days) occurred after 8.75 mu g in follicles to 28 to 31 mm.

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