Follicular dynamics after treatment with hCG for ovulation induction in mares

In this study the use of hCG for induction of ovulation is described. Factors such as follicle diameter at the time of administration of hCG (3000 IE hCG i.v.), follicular growth after hCG and the rate of double ovulations were evaluated. A total of 168 mares presented for artificial insemination were used. In 249 estrous periods hCG was given to mares exhibiting standing estrous when a minimum follicle diameter of 30 mm and a well developed edema of the endometrium could be detected by ultrasonography. In nine estrous periods ovulation occurred within 24 hours after hCG. The majority of mares (216; 86.7%) ovulated 24 to 48 hours after hCG and in 24 cases ovulation was delayed beyond 48 hours. Follicle size at the time of hCG administration (30-34 mm, 35-39 mm, > or = 40 mm) had no influence on the percentage of mares ovulating 24 to 48 hours after hCG (89.2%, 87.9%, and 83.7%, respectively). Double ovulations could be observed in 17.7% of estrous periods. The one cycle pregnancy rate was not influenced by follicle size (small 45.9%; medium 41.6%; large 47.5%). Repeated treatments with hCG during successive estrous cycles within one year did not influence the rate of responding to hCG. Mares in standing estrous respond well to hCG if a minimum follicle size of 30 mm and a well developed endometrial folding is present.     

The probable identification of monozygous twin embryos in mares

Observations based upon ultrasonic examination in early pregnancy of over 6000 brood mares between 1988 and 1995 identified 956 sets of multiple pregnancies. Ovaries of all mares were examined during estrus and up to four days after ovulation, and again at early (13 to 17 days) and later pregnancy diagnoses. By detailed recording of all identifiable follicles and corpora lutea, it was concluded that 18 twin and seven triplet pregnancies resulted from only single and double ovulations, respectively. The apparent incidence of monozygous twin embryos was at least 2.6%.     

Embryo reduction before day 11 in mares with twin conceptuses

Incidence of embryo reduction (natural elimination of one member of a twin set) before d 11 was studied by comparing the number of ultrasonically detected conceptuses per ovulation between single and double ovulators. Effect of unilateral (n = 24) vs bilateral (n = 26) double ovulations on the incidence of embryo reduction also was considered. Each of 50 double-ovulating mares was matched with two single ovulators yielding 100 ovulations, or potential embryos, per group. Frequency with which an ovulation resulted in a conceptus was greater for single ovulators (85%, P less than .01) and for bilateral double ovulators (77%, P less than .05) than for unilateral double ovulators (60%). The difference between single and bilateral ovulators was not significant. Expected frequencies for none, one or two conceptuses per mare for double ovulators were calculated using the d-11 pregnancy rate for the single ovulators (85%). For unilateral ovulators, but not for bilateral ovulators, observed frequencies of none, one or two conceptuses were different (P less than .05) from expected (observed and expected, respectively, for no conceptuses, 29% and 2%; one conceptus, 21% and 26%; two conceptuses, 50% and 72%). Results did not indicate the existence of an embryo reduction phenomenon before d 11 in bilateral ovulators; each ovum had the same chance (no significant difference) of developing into a d-11 conceptus as an ovum in single ovulators. In unilateral double ovulators, the lower d-11 pregnancy rate per ovum, compared with bilateral ovulators and single ovulators, was attributable to a greater frequency of mares with no embryonic vesicles rather than to a greater frequency of mares with one vesicle.(ABSTRACT TRUNCATED AT 250 WORDS)     

The nature of embryo reduction in mares with twin conceptuses: deprivation hypothesis

Ultrasonography was used to determine whether there is embryo reduction in mares with unilaterally fixed twins when a major portion of the vascularized area of the wall of one of the embryonic vesicles is in apposition with the wall of the adjacent vesicle, rather than with the endometrium (deprivation hypothesis). In addition, the effect of ovulatory pattern (synchronous and asynchronous) on the incidence of embryo reduction was studied. Twin vesicles were ultrasonically detected on days 11 to 15 (ovulation = day 0) and were examined daily until there was embryo reduction or until day 40. In 31 mares with twin embryonic vesicles, unilateral fixation (71%) was more frequent (P less than 0.05) than was bilateral fixation (29%). In 28 mares with known ovulatory patterns, synchronous ovulations did not affect the type of fixation (9/17 unilateral and 8/17 bilateral); however, for asynchronous ovulators the frequency of unilateral fixation (10/11) was greater (P less than 0.01) than the frequency of bilateral fixation (1/11). The incidence of embryo reduction was greater (P less than 0.01) for unilateral fixation (14/19) than for bilateral fixation (0/9) and was greater (P less than 0.05) for asynchronous ovulators (9/11) than for synchronous ovulators (5/17). In mares with embryo reduction, the reduction was complete before detection of both embryo propers (early reduction) in 10/14 and after detection of both embryo propers (late reduction) in 4/14.(ABSTRACT TRUNCATED AT 250 WORDS)     

Increased Frequency of Double Ovulations after Induction of Luteolysis with Exogenous Prostaglandin F2α

The effect of induction of luteolysis by intramuscular treatment with prostaglandin F2α (PGF) on the frequency of double ovulations and formation of hemorrhagic anovulatory follicles (HAFs) was studied. The PGF (5 mg) was given 10 days after ovulation (n = 47 estrous cycles). No treatment or sham injection was used for control estrous cycles (n = 39). After treatment, the mares were scanned by transrectal ultrasonic imaging every 2 days until the largest follicle reached 25 mm and every day thereafter until the outcome of all follicles of at least 25 mm was determined. The frequency of two ovulations during the posttreatment ovulatory period was greater (P < .03) in the treated group (17%) than in the controls (3%). The combined frequency of two ovulations or one ovulation and one HAF also was greater (P < .002) in the treated group (30% vs. 5%). Equine veterinarians should be aware that PGF induction of luteolysis may increase the frequency of double ovulations or HAFs.     

Effect of exogenous progesterone administration on luteal sensitivity to PGF during the early development of the corpus luteum in mares and cows

The objective of this study was to determine the effect of exogenous progesterone administration at ovulation and during the early development of the CL, on its future sensitivity to a single administration of PGF2a in mares and cows. Horse Retrospective reproductive data from an equine clinic in the UK during three breeding seasons were used. Mares were divided into: control group, cycles with single ovulations; double ovulation group cycles with asynchronous double ovulations; and PRID group: cycles with single ovulations and treatment with intravaginal progesterone device (CIDR) immediately after the ovulation. All mares were treated with d‐cloprostenol (PGF) at either: (i) 88 hr; (ii) 96 hr; (iii) 104 hr; or (iv) 112 hr after the last ovulation. Cattle A total of nine non‐lactating Holstein cows were used. All cows were administered PGF14 d apart and allocated to one of two groups control group GnRH was administered 56 hr after the second PGF administration. CIDR group CIDR was inserted at the same time of GnRH administration. All cows were administered PGF at 120 hr post‐ovulation. The complete luteolysis rate of mares with double ovulation (66.7%) and those treated with exogenous progesterone (68.4%) was significantly higher than the rate of mares with single ovulation (35.6%) at 104 hr. In the cow, however, the treatment with CIDR did not increase the luteolytic response in cows treated at 120 hr post‐ovulation. In conclusion, the degree of complete luteolysis can be influenced by increasing the concentration of progesterone during the early luteal development in mares.     

Diagnosis and correction of twin pregnancy in the mare

Reproductive Physiology 1. Twin pregnancies result in high rates of abortion, stillbirth, and neonatal mortality. 2. Twins develop subsequent to multiple ovulations. Multiple ovulations are related to breed, parity, and mare history. Multiple ovulations are most frequently seen in Thoroughbred and Draft mares. Multiple ovulations are more common in barren and perhaps maiden mares than in lactating mares, and they are more common in certain individual mares. 3. Equine embryos are motile in the uterus from the time of first detection (Days 9 to 10) until fixation (Day 16). They are frequently located in the uterine body on Days 9 and 10. 4. Twin embryos have a pattern of motility and fixation similar to that of single embryos, and fixation is more frequently unilateral than bilateral (70 per cent versus 30 per cent, respectively). 5. Mares have an efficient natural embryo-reduction mechanism to eliminate excess (greater than 1) embryos resulting from multiple ovulations. Natural embryo reduction is more successful in unilateral than bilateral twin pregnancies (89 per cent versus 11 per cent successful reduction, respectively). 6. After the establishment of endometrial cups (Days 35 to 40), mares that are aborted will frequently not cycle for several months. Management of Twin Pregnancy 1. Breed all mares regardless of the number of preovulatory follicles. Withholding mares with preovulatory follicles from breeding does not decrease the incidence of twin pregnancy, but it decreases the overall pregnancy rate and results in a loss of breeding time. 2. Check all mares for twins, regardless of the number of detected ovulations.(ABSTRACT TRUNCATED AT 250 WORDS)     

Strategies for Using eFSH for Superovulating Mares

The standard treatment for superovulation of mares is to administer equine follicle-stimulating hormone (eFSH) for 4 to 5 days to stimulate multiple follicles and human chorionic gonadotropin (hCG) to induce synchronous ovulations. Objectives of this study were: (1) to determine whether a short-term (3-day) eFSH treatment protocol would result in similar ovulation and embryo recovery rates compared with the standard eFSH protocol; (2) to determine the efficacy of a decreasing dose of eFSH (step-down protocol) on ovulation rate and embryo recovery; (3) to compare the efficacy of hCG and recombinant equine luteinizing hormone (reLH) for inducing ovulation in FSH-treated mares; and (4) to compare embryo recovery rates and embryo size when mares are flushed at 6.5 or 7.0 days after ovulation. Forty light-horse mares were used in 2005 (experiment 1) and 20 different mares were used in 2006 (experiment 2). In experiment 1, mares were randomly assigned to one of three treatment groups: (1) untreated controls, (2) standard eFSH treatment (12.5 mg intramuscularly twice daily), and (3) 3-day eFSH treatment. In experiment 2, mares were randomly assigned to one of four treatments: (1) untreated controls, (2) standard eFSH protocol, (3) 3-day eFSH treatment, and (4) step-down eFSH treatment (12.5 mg twice daily day 1, 8.0 mg twice daily day 2, 4.0 mg twice daily day 3). Within each treatment, mares were given either hCG (2,500 IU) or equine LH (750 mg, EquiPure LH; reLH) to induce synchronized ovulations. Embryo recovery was performed either 6.5 or 7.0 days after ovulation. In experiment 1, numbers of preovulatory follicles and ovulations were less for mares in the 3-day treatment group than the standard group, but were greater than for controls. Embryo recovery per flush was higher in the standard group (2.6) than the 3-day eFSH treatment (0.8) or control groups (0.8). In experiment 2, the number of preovulatory follicles and number of ovulations were greater in the standard and 3-day treatment groups than in control and step-down groups. The percent embryo recovery per ovulation and mean embryo grade were similar for all groups; however, the embryo recovery per flush was higher for mares in the standard treatment than controls (1.3 vs 0.6) but was similar to the 3-day (1.1) and step-down (0.8) treatments. Embryo recovery was similar for flushes performed on days 6.5 and 7.0 post-ovulation. The percentage of control mares ovulating within 48 hours in response to hCG or reLH was similar. In contrast, a higher percentage of eFSH-treated mares ovulated within 48 hours in response to reLH than hCG (92% vs 71%). In both years, the 3-day eFSH treatment protocol resulted in a greater number of preovulatory follicles and a greater number of ovulations than untreated controls. Unfortunately, the increased ovulation rate for mares administered eFSH for 3 days did not result in a greater number of embryos recovered per flush in either year. Use of a step-down eFSH treatment protocol resulted in fewer preovulatory follicles, fewer ovulations, and fewer embryos as compared with the standard eFSH treatment. In conclusion, the standard eFSH treatment resulted in a greater embryo recovery rate per cycle than either the 3-day or step-down treatment protocols. Recombinant equine LH was more effective than hCG in causing ovulation in eFSH-treated mares.     

Successful reduction of a monozygotic equine twin pregnancy via transabdominal ultrasound‐guided cardiac puncture

In horses, twin pregnancy is pathological and represents a potentially life‐threatening condition to the mare and foal. Twinning occurs in approximately 2% of pregnancies. Of these, the majority of cases are dizygotic twins, resulting from 2 ovulations and monozygotic twins are rare. A 12‐year‐old Quarter Horse mare was presented for breeding management with shipped cooled semen and embryo transfer. Seven days post ovulation, a single late morula/early blastocyst was recovered and transferred immediately to a recipient mare. Thirty‐six days after transfer, transrectal ultrasound examination revealed the presence of 2 embryos. A transcutaneous reduction of one of the fetuses was performed successfully at 128 days of gestation. This report is the first to describe a successful reduction of monozygotic twins by transcutaneous ultrasound‐guided cardiac puncture.     

Relationship between pharmacological induction of estrous and/or ovulation and twin pregnancy in the Thoroughbred mares

The aim of this study was to evaluate the possible relationship of pharmacological induction of estrous and/or ovulation with the occurrence of twin pregnancies in Thoroughbred mares. Out of 680 mares, 356 received one of the following treatments during the estrous cycle in which they became pregnant: injection of 0.5mg of cloprostenol at the ultrasonographic detection of a CL (n=86); injection of 5000 IU human chorionic gonadotropin (hCG) immediately before mating (n=221); injection of 0.5mg of cloprostenol at the ultrasonographic detection of a CL plus injection of 5000 IU hCG immediately before mating on cloprostenol-induced estrous (n=49). The other 324 mares, not treated for induction of estrous or ovulation in the estrous cycle resulting in pregnancy, were used as control group. The occurrence of twin and single pregnancies in treated and control mares underlines that the percentage of twin pregnancy in treated mares (16.6%) was statistically significantly higher (P<0.0001; odds ratio, OR=2.87) than the percentage of twinning in the control group (6.5%). Comparison of the occurrence of twins between treatments revealed a statistically significant difference between mares treated with hCG alone compared to animals given prostaglandin F2alpha (PGF2alpha) plus hCG. The results show a statistically significant difference for each treatment compared to controls, with the least difference (P<0.05; OR=2.18) for the comparison between hCG treatment group and controls, a significance of P<0.01; OR=3.05 for the comparison between PGF2alpha treatment and controls, and a highly statistically significant difference (P<0.0001; OR=6.37) for the comparison between PGF2alpha plus hCG-treated animals and controls.     

Effect of eFSH on Ovarian Cyclicity and Embryo Production of Mares in Spring Transitional Phase

The use of equine FSH (eFSH) for inducing follicular development and ovulation in transitional mares was evaluated. Twenty-seven mares, from 3 to 15 years of age, were examined during the months of August and September 2004, in Brazil. Ultrasound evaluations were performed during 2 weeks before the start of the experiment to confirm transitional characteristics (no follicles larger than 25 mm and no corpus luteum [CL] present). After this period, as the mares obtained a follicle of at least 25 mm, they were assigned to one of two groups: (1) control group, untreated; (2) treated with 12.5 mg eFSH, 2 times per day, until at least half of all follicles larger than 30 mm had reached 35 mm. Follicular activity of all mares was monitored. When most of the follicles from treated mares and a single follicle from control mares acquired a preovulatory size (≥35 mm), 2,500 IU human chorionic gonadotropin (hCG) was administered IV to induce ovulation. After hCG administration, the mares were inseminated with fresh semen every other day until ovulation. Ultrasound examinations continued until detection of the last ovulation, and embryo recovery was performed 7 to 8 days after ovulation. The mares of the treated group reached the first preovulatory follicle (4.1 ± 1.0 vs 14.9 ± 10.8 days) and ovulated before untreated mares (6.6 ± 1.2 vs 18.0 ± 11.1 days; P < .05). All mares were treated with prostaglandin F_2α (PGF_2α), on the day of embryo flushing. Three superovulated mares did not cycle immediately after PGF_2α treatment, and consequently had a longer interovulatory interval (22.4 vs 10.9 days, P < 0.05). The mean period of treatment was 4.79 ± 1.07 days and 85.71% of mares had multiple ovulations. The number of ovulations (5.6 vs 1.0) and embryos (2.0 vs 0.7) per mare were higher (P < 0.05) for treated mares than control mares. In conclusion, treatment with eFSH was effective in hastening the onset of the breeding season, inducing multiple ovulations, and increasing embryo production in transitional mares. This is the first report showing the use of FSH treatment to recover embryos from the first cycle of the year.     

Follicle stimulating hormone, luteinising hormone and progesterone concentrations in the blood of thoroughbred mares exhibiting single and twin ovulations

The concentrations of follicle stimulating hormone, luteinising hormone and progesterone were measured in serial blood samples taken throughout one or more oestrous cycles from 12 Thoroughbred mares, some of which exhibited single and others twin ovulations. The resulting profiles clearly demonstrated that no simple relationship exists between circulating gonadotrophin levels and subsequent ovulation rate in the mare. However, plasma progesterone concentrations during dioestrus are, as expected, higher following twin than single ovulations. The findings suggest that the underlying cause of twin ovulation in some mares may exist at the ovarian end of the pituitary-ovarian axis which controls follicular development and ovulation.     

Ovulation,Pregnancy Rate and Early Embryonic Development in Vernal Transitional Mares Treated with Equine‐ or Porcine‐FSH

The objective of this study was to compare the efficacy of purified equine‐ and porcine‐FSH treatment regimes in mares in early vernal transition. Mares (n = 22) kept under ambient light were examined ultrasonographically per‐rectum, starting January 30th. They were assigned to one of two treatment groups using a sequential alternating treatment design when a follicle ≥ 25 mm was detected. In the eFSH group, mares were treated twice daily with equine‐FSH, and in the pFSH group mares were treated twice daily with porcine‐FSH; treatments were continued until follicle(s) ≥ 35 mm, and 24 h later hCG was administered. Oestrous mares were inseminated with fresh semen and examined for pregnancy on days 11–20 post‐ovulation. In the eFSH group, 11/11 (100%) mares developed follicle(s) ≥ 35 mm, 8/11 (73%) ovulated and 6/8 (75%) conceived. In the pFSH group, 5/11 (45%) developed follicle(s) ≥ 35 mm, 4/11 (36%) ovulated and 3/4 (75%) conceived. Treatment with eFSH resulted in a greater ovarian stimulation; higher number of pre‐ovulatory‐sized follicles, higher number of ovulations and higher number of embryos (p < 0.05). Following ovulation, serum progesterone concentrations were correlated with the number of CLs and supported early embryonic development; maternal recognition of pregnancy occurred in all pregnant mares. We concluded that eFSH can be used to effectively induce follicular growth and ovulation in vernal transitional mares; however, if bred, diagnosis and management of twins’ pregnancies would be required prior to day 16 because of the increased risk of multiple embryos per pregnancy. Conversely, the current pFSH treatment regime cannot be recommended.     

Evaluation of ovulation rate and ovarian phenotype in puberal heifers from a cattle population selected for increased ovulation rate

Long-term selection for increased ovulation rate (1984 to 2002) has resulted in a unique ovarian phenotype in the MARC Twinner cattle population. Ovulation rate and frequency of bilateral ovulations were examined by rectal palpation in 29,547 estrous cycles for 3,910 heifers (12 to 18 mo of age) in this population. Bilateral ovulations (one corpus lutuem [CL] on each ovary) were of interest because bilateral twin pregnancies result in decreased dystocia and increased calf survival. Ovulation rate increased linearly at a rate of 0.026 CL per year, and it currently averages 1.48 +/- 0.04 CL per estrous cycle. Concurrent with the increase in ovulation rate, the frequency of triplet ovulations increased from 0% to 2.3 +/- 0.8% (P < 0.001). Ovulation rate of both the right and left ovary increased equally at a rate of 0.013 CL per year, and mean ovulation rate of the right ovary remained greater than mean ovulation rate of the left ovary throughout the study (0.66 vs. 0.55 +/- 0.003 CL per estrous cycle; P < 0.001). Although correlations were low, ovulation rate of one ovary was negatively correlated (P < 0.001; r = -0.07) with ovulation rate of the same ovary in the previous estrous cycle, but positively correlated (P < 0.001; r = 0.13) with the contralateral ovary of the previous estrous cycle. The proportion of bilateral ovulations averaged 55.7 +/- 0.7%, a value greater than the predicted 49.5% (P < 0.001). In addition to dystocia and retained placenta, triplet pregnancies increase the incidence of pregnancies gestating fetuses of opposite sexes and subsequent incidence of freemartins; thus, selection pressure on ovulation rate may need to be adjusted in the MARC Twinner population. The proportion of bilateral ovulations in the population is greater than expected, and this may be an economically important trait, which will respond to selection and be beneficial for improving bovine reproductive efficiency. Understanding factors controlling the increased functional activity of the right ovary and bilateral ovulations may provide further insights into the mechanisms controlling follicle selection and methods to improve reproductive management of cattle.     

The Use of Equine Follicle Stimulating Hormone to Increase Equine Chorionic Gonadotropin in the Pregnant Mare

Equine chorionic gonadotropin (eCG), obtained from pregnant mares, is used for assisted reproductive technologies in laboratory rodents and livestock. The objective of the present study was to use equine follicle-stimulating hormone (eFSH) to increase the incidence of twin pregnancies, through multiple ovulations, and increase eCG. Nineteen light horse–type mares were enrolled in the study. The control group (n = 9) was bred with fresh or cooled semen and given human chorionic gonadotropin (hCG) at the time of breeding. The second group (n = 10) was given 12.5 mg of eFSH intramuscularly twice a day beginning 5–7 days after ovulation. Prostaglandin F2α was administered intramuscularly the second day of eFSH treatment. Treatment with eFSH continued until follicles were >35 mm in diameter, and mares were then given no treatment for 36 hours. The mares were then bred with fresh or cooled semen from the same stallion as the control group and given hCG. Blood samples were taken weekly from day 35 to day 105 after ovulation. Serum concentration of eCG was obtained, and data were analyzed with multivariate analysis using the mixed procedure. Significance was set at P < .05. Data were combined for all mares carrying twins and compared with those carrying singletons. The group of mares carrying twins had higher peak concentrations of eCG and higher values for area under the curve compared with mares carrying singletons (P < .05). These results suggest inducing twins could be a method used to increase eCG production.     

The Effect of Cloprostenol on the Incidence of Multiple Ovulation and Anovulatory Hemorrhagic Follicles in Two Mares: A Case Report

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 < .000) to develop hemorrhagic anovulatory follicles than spontaneous cycles. The incidence of multiple ovulation was higher in induced cycles than in spontaneous cycles in one of the two mares.     

Reproductive Parameters of Mangalarga Marchador Mares in a Commercial Embryo Transfer Programme

The objective of this study is to evaluate the reproductive efficiency in donors and recipient Mangalarga Marchador mares in commercial programmes of embryo transfer (ET) and the effects of some reproductive characteristics and ET methodology on conception rates in the recipient mares. A total of 1140 flushing procedures were performed and 830 embryos (72.8%) were recovered. There were no differences between the rates of embryonic recovery in the different breeding seasons (p > 0.05) and 92.8% of the recovered embryos were 8–9 days old. There was no difference in the embryonic recovery regarding the collection order from the first to the ninth embryo collection along the breeding season, as well as among mares inseminated during the foal heat or subsequent cycles (p > 0.05). Pregnancy rates observed in the total period of all reproductive seasons at 15, 30, 45 and 60 days of pregnancy were 73.4, 69.9, 66.7 and 64.5%, respectively. Differences in pregnancy rate and early embryonic loss rates were not observed between embryos transferred immediately after collection (66.8% and 13.5%) and embryos transported at room temperature for periods of <1 h (62.9% and 14.4%; p > 0.05). Pregnancy rates were higher when the interval between ovulations of donor and recipient mares remained between ?3 and ?2 days (p < 0.05), and the lowest rates were observed for intervals of ?6 days (p < 0.05) with intermediary values for intervals of ?1, 0 and +1 (p > 0.05). Embryonic loss rates, however, did not differ between intervals of ovulation’s synchronism between donor and recipient mares (p > 0.05). This flexibilization in the ovulatory synchronism between donor and recipient mares optimizes the use of recipient mares, thus reducing costs and facilitating management of horse breeding farms.     

Effectiveness of a novel prostaglandin analog in postpartum mares and mares with early season anestrus

Contents Fifty thoroughbred mares, located at Central-Southern Brazil near Sao Paulo (13 anestrous maiden, 18 anestrous barren mares and 19 postpartum mares) were treated with one to three injections, 48 hrs apart, of 2 mg of the novel PGF analog K 11941*, during the early part of the breeding season. Early season anestrus in these problem mares was compounded by the adverse effects of a drought. Plasma progesterone determinations revealed unexpectedly elevated plasma progesterone levels in 61.5% of the maiden mares, in 77.8% of the barren mares and in 68.4% of the postpartum mares (20 to 25 days postpartum). Treatments with K 11941 initiated luteolysis, heat and ovulations in 91.4, 45.5 an 63.3% of these mares, respectively, but initiated also heat and ovulation in 13% and 33% of mares with baseline progesterone levels. Treatments initiated covert and overt cyclic functions in 17 and 12 of those animals which did not conceive immediately. Fifteen animals with recurrent anestrus received further treatment with K 11941. Ten mares cycling silently were force bred when palpations indicated ovulatory follicles, and 7 conceived. Of the 50 mares treated, 38 became pregnant (76%: maiden mares: 76.9%; barren mares: 77.8% and postpartum mares: 73.7%) with breeding indices of 1.9, 1.36 und 1.57, respectively; and 37 mares gave birth to a live foal (74%), At the same stud, 138 control mares had a foaling rate of 82.6%.     

Superovulation in Mares Using Recombinant Equine Follicle Stimulating Hormone: Ovulation Rates,Embryo Retrieval,and Hormone Profiles

The purpose of this research was to determine whether treatment with varying doses of recombinant equine follicle stimulating hormone (reFSH) stimulates the development of multiple follicles and ovulations and increases the number of embryos recovered in the mare. Therefore, because reFSH can be cloned in repeatable, sizeable quantities, it could be used as a tool to enhance superovulation in mares. In experiment 1, the number of preovulatory follicles, ovulations, and embryos recovered per flush was greater in the 0.85 mg reFSH group than in the control group; however, the embryo per ovulation rates were similar. Plasma inhibin and estradiol concentrations were greater in treated mares around the time of ovulation as compared with the control group, whereas concentrations of luteinizing hormone remained low throughout the treatment, ovulation, and postovulation. In treated mares, concentrations of follicle stimulating hormone increased during therapy and before ovulation, but decreased postovulation. In experiment 2, varying doses of reFSH (0.35, 0.50, and 0.65 mg) and 12.5 mg of Bioniche equine follicle stimulating hormone (eFSH) increased the number of preovulatory follicles as compared with control group. The greatest number of ovulations was induced by treatment with 12.5 mg eFSH, 0.5 mg reFSH, and 0.65 mg reFSH. The highest number of embryos recovered per flush was found with treatments of eFSH and 0.65 mg reFSH. However, the embryo per ovulation rates were similar in all treatment groups, including the control group. In experiment 3, reFSH (0.5 and 0.85 mg) and eFSH (12.5 mg) given twice daily showed a similar increase in the number of pre-ovulatory follicles and ovulations. A single daily treatment of reFSH (0.85 mg) as well as the twice daily dose of eFSH was determined to increase follicular activity. In conclusion, reFSH was as effective as eFSH in increasing the number of follicles ≥35 mm, ovulation rates, and embryo recovery rates per flush compared with the control group.     

Transcervical embryo transfer in performance mares

Pregnancy was established by transcervical transfer of embryos from performance mares into recipient mares. Estrus was synchronized between donor (n = 17) and recipient (n = 43) mares. After a greater than or equal to 25-mm follicle was detected, donor mares were bred artificially daily until ovulation. Day of ovulation was recorded. Uterine flushes (n = 111) were performed on donor mares 7 days after ovulation, and recovered embryos were transferred transcervically to recipient mares within 2 hours. Embryos were recovered from 40.5% of uterine flushes. Of transferred single embryos, 65.7% resulted in pregnancy, detectable by ultrasonographic examination 23 days after transfer. Only 35.3% of twin embryos resulted in pregnancy. Results over a 4-year period were as follows: uteri were flushed on 14, 44, 31 and 22 occasions, and 8, 21, 15, and 11 embryos were recovered (1 embryo was not transferred), with 6, 11, 4, and 6 resulting in 30-day pregnancy in years 1 to 4, respectively.