Management Strategies Aiming to Improve Horse Welfare Reduce Embryonic Death Rates in Mares

The objective of this retrospective study was to evaluate the effect of management strategies aiming to improve animal well‐being on pregnancy and embryonic death (ED) rates. Breeding records of a cohort of 1206 Thoroughbred mares brought to a stallion station facility, to be bred with the stallions housed there, were evaluated during ten breeding seasons. Mares were blocked according to management strategies in two groups: Stress and Relax. Strategies used to improve animal well‐being (Relax group) were as follows: stopping the teasing routine, reducing or eliminating stall confinement, reducing the number of mares per group and maintaining herd stability during the breeding season. In barren mares, the pregnancy rate was higher in the Relax group (91.8%) when compared to the observed in Stress group (84.7%). However, no difference in pregnancy rates were observed (Stress = 85.2% vs. Relax = 86.2) in foaling mares. ED rate was higher in barren and foaling mares of the Stress group mares (25.5% and 26.8%, respectively) compared with the Relax group (16.1% and 14.7%, respectively). No significant differences were observed on foal heat pregnancy rate between groups; yet, the embryo loss on foal heat was significant reduced in Relax mares (Relax = 8.7% vs Stress = 24.5%). In conclusion, management strategies aimed to reduce social stress can reduce early pregnancy losses and the average cycles per pregnancy, improving reproductive performance in mares.     

The Activity and Localization of 3β-hydroxysteroid Dehydrogenase/Δ5-Δ4 Isomerase and Release of Androstenedione and Progesterone by Uterine Tissues During Early Pregnancy and the Estrous Cycle in Pigs

Steroid hormones are produced by the porcine uterus. We hypothesized that the uterus in pigs possesses active 3β-hydroxysteroid dehydrogenase/Δ⁵-Δ⁴ isomerase (3β-HSD) responsible for progesterone and androstenedione production, that uterine steroids may supplement the amount of steroid hormones produced by embryos and corpus luteum and that these steroids are necessary for maintenance of pregnancy. In this study, we examined 1) endometrial and myometrial expression of 3β-HSD mRNA, 2) uterine 3β-HSD protein activity and 3) in vitro production of A₄ and P₄ by uterine slices harvested from pigs on days 10 to 11, 12 to 13 and 15 to 16 of pregnancy and the estrous cycle. The expression of 3β-HSD and the presence and activity of 3β-HSD protein were different in the endometrium and the myometrium during the examined periods of pregnancy and the estrous cycle. Production of A₄ by the endometrium and myometrium was highest on days 12 to 13 of pregnancy and the estrous cycle. Endometrial secretion of P₄ did not differ in the course of early pregnancy and on the respective days of the estrous cycle. The gravid myometrium was the highest source of P₄ in pregnant pigs on days 12 to 13. The release of P₄ by the cyclic myometrium rose during the examined days of the estrous cycle. The steroidogenic activity of the uterus, as described in this study, may support early pregnancy or the luteal phase of the estrous cycle in pigs.     

Conception rate,uterine infection and embryo quality after artificial insemination and natural breeding with a stallion carrier of Pseudomonas aeruginosa: a case report

Background

Pseudomonas aeruginosa may cause venereal disease and infertility in horses. A Pseudomonas aeruginosa - carrier stallion, often unresponsive to artificial vagina collection, was used to naturally breed mares. Semen collected from the same stallion was also used to perform artificial inseminations. Pregnancy rates, embryo quality and incidence of uterine infection were compared between inseminated or naturally-bred mares.

Methods

P. aeruginosa was isolated from swabbing of the penis, prepuce and distal urethra of the stallion. Before being bred or inseminated, clitoral/vestibular samples were collected from all mares, and cultured for isolation of P. aeruginosa. At the first observed estrus, endometrial swabs were also collected. All mares subjected to natural mating (NS) were re-evaluated for P.aeruginosa by culture of clitoral and endometrial swabs. Artificial inseminations (AI) were performed either with fresh-extended semen (11 AI/7 mares) or frozen semen (10 AI/7 mares). The stallion was also used to breed 3 mares (4 services). For embryo collection, 2 mares were inseminated with fresh-extended semen (1 AI/mare), and 2 additional mares were inseminated with frozen semen (2 AI/mare). Two mares were naturally-bred with a total of 9 services, for embryo collection. All mares were examined after AI or natural service (NS), for uterine pathologies. Embryo recoveries were attempted passing a catheter with inflatable cuff connected to a sterile flexible 2-way flushing catheter, through the cervix. Flushed media was recovered into an Em-Con filter, and embryos searched using a stereoscope. Embryos were graded from 1 (excellent) to 4 (degenerated/dead).

Results

Pregnancy rates obtained after NS was 50% per cycle. However, more than half of the NS resulted in uterine disease, while uterine pathology was seen only in 22% of the time following AI. Half of the mares bred by NS got positive to P. aeruginosa. Percentage of embryo recovery rates was identical after AI or NS (66.7%). The 4 embryos recovered after AI were classified as Grade 1, while after NS only 2 out of the 6 recovered embryos were Grade 1.

Conclusion

a) there was no evidence of reduced fertilization after AI or NS, b) a numerically higher incidence of uterine disease was noticed after NS, c) venereal transmission of P. aeruginosa after NS was confirmed, d) a lower percentage of G1 embryos may be obtained after NS. Overall, the data supports the indication for P. aeruginosa-carrier stallions to be bred by AI rather than by NS, and raises the possibility that P. aeruginosa may affect embryo quality.     

Retrospective study on the incidence of postinsemination uterine fluid in mares inseminated with frozen/thawed semen

Uterine fluid accumulation has been reported after insemination or natural breeding of mares. This retrospective study examined the factors affecting the incidence of uterine fluid after insemination of frozen semen. Specifically, this study determined the association between mare age, reproductive status, fluid accumulation, and pregnancy rates in mares. Records were available from 283 warmblood mares throughout 496 cycles. Mares were divided into maiden, foaling, and barren and age groups of 3 to 9, 10 to 16, and more than 16 years. Mares were inseminated only once with frozen semen within 4 to 8 hours before or after ovulation. Ultrasound examinations were performed 12 to 18 hours after insemination. A depth of at least 20 mm of fluid was considered significant. Mares with less than 20 mm were treated with oxytocin, and those with more than 20mm of fluid were given oxytocin and uterine lavage. Pregnancy determination was performed at 14 to 16 and 30 to 50 days after ovulation. Fluid level of more than 20 mm was recorded in 25% of the cycles. Barren mares and aged mares (10-16 and > 16 years) had a higher incidence of uterine fluid accumulations. Per-cycle pregnancy rate was lower (45%) in mares with uterine fluid than in mares without uterine fluid (51%). This difference was primarily due to the reduction in fertility of mares who were older than 16 years and retained fluid after insemination. Apparently, oxytocin and lavage treatments provided acceptable fertility in the other groups of mares that had uterine fluid.

Introduction

Use of equine frozen semen is accepted by the majority of horse registries. According to several field studies,[1, 2, 3, 4 and 5] insemination of frozen semen has resulted in acceptable pregnancy rates. Postbreeding fluid accumulation is a physiologic inflammation that clears the uterus of foreign material such as excess spermatozoa, seminal plasma, bacteria, and extenders. [6, 7, 8, 9 and 10] Uterine fluid can be easily diagnosed with ultrasonography. [10, 11 and 12] Persistent postbreeding uterine fluid has been associated with a decrease in fertility after natural mating or artificial insemination (AI) of fresh semen. [11, 12 and 13] Predisposing factors to persistent fluid accumulations are reduced myometrial contractions, poor lymphatic drainage, large overstretched uterus, and cervical incompetence. [7, 14 and 15] Normal mares are able to expel uterine fluid quickly after inseminations, whereas susceptible mares accumulate fluid in their uterine lumen for more than 12 hours after breeding or insemination. [10]It is commonly stated that insemination with frozen semen leads to greater post-AI fluid accumulation than insemination with fresh or cooled semen or after natural mating. Apparently, there is only 1 controlled study on this comparison.[7] The authors reported that infusion of frozen semen resulted in a greater inflammatory response than natural breeding. In a field study, [16] 16% of mares naturally mated had persistent postbreeding fluid accumulations compared with a 30% rate reported for mares inseminated with frozen semen. [1 and 2] More recently, Watson et al. [17] reported a postbreeding fluid accumulation rate of 16%, which is identical to that reported for natural mating. [16] It is difficult to compare studies because details of mare selection and insemination or breeding frequencies are not always reported. Obviously, a higher proportion of barren and aged mares in a study would increase the incidence of postbreeding fluid accumulation. [1 and 2]The study presented herein was a retrospective study designed to determine the incidence of postbreeding fluid accumulation in a large number of mares inseminated with frozen semen. Associations were determined between mare age, reproductive status and fluid accumulation, and pregnancy rate in mares with and without uterine fluid accumulation.

Materials and methods

Mares

Records were available from 283 warmblood mares inseminated with frozen semen at the Cristella Veterinary Clinic in Italy during 1998 to 2001. Mares ranging in age from 3 to 20 years were inseminated with semen that was frozen in 10 centers and was from 34 stallions. The broodmare population was subdivided into 3 reproductive groups: 89 maiden mares (mean age, 7.2 years), 106 foaling mares (mean age, 9.4 years), and 87 barren mares (mean age, 11.9 years). Maiden mares older than 7 years were selected with biopsy scores of 1 or 2 only. Barren mares were open for no more than 2 consecutive seasons and had negative cytology and bacteriology scores. Age groups were divided as follows: 3 to 9 years (n = 132), 10 to 16 years (n = 137) and older than 16 years (n = 14). Data from 496 cycles were used. Distribution of the estrous cycles was 172, 157, and 167 in the maiden, foaling, and barren groups, respectively; and 224, 244, and 28 in the youngest, intermediate, and oldest groups, respectively.

Mare reproductive management and artificial insemination protocol

During estrus, all mares underwent a daily ultrasound examination with a 5-mHz transrectal probe (SA 600 Vet; Medison Inc., Seoul, South Korea) until 1 or more 35-mm ovarian follicles were detected. Ovulation was then induced by the intravenous administration of 2000 IU of human chorionic gonadotropin (hCG). Ultrasound examination was performed 12 hours after hCG treatment and then every 4 to 8 hours until ovulation occurred. Mares were inseminated only once within a period of 4 to 8 hours before or after ovulation. The semen used was thawed according to the distribution center's instructions and had the following minimum post-thaw quality requirements: not less than 200 × 10⁶ progressively motile spermatozoa per dose and a minimum of 30% progressive spermatozoal motility. Foaling mares were not inseminated at their first postpartum (“foal heat”) estrous period, because pregnancy rates are recognized to be lower than during the subsequent estrous periods.[18] During the first postpartum estrus, ovarian ultrasound scan examinations were performed every 2 to 3 days until an ovulation was detected. A prostaglandin F₂α injection was given 5 days later to short-cycle the mare.

Postinsemination monitoring

An ultrasound examination of the reproductive tract was performed 12 to 18 hours after insemination to detect any intrauterine fluid accumulation. The presence and depth of intrauterine fluid was recorded. Twenty millimeters or more of grade II or III intrauterine fluid[19] was recorded as a significant amount of fluid. Mares with less than 20 mm of fluid were treated with an intravenous injection of 20 IU oxytocin. For mares with more than 20 mm of fluid, oxytocin was administered, and the uterus was flushed daily with buffered saline solution: 1-L aliquots were infused and recovered until the recovered fluid was clear. In these mares, oxytocin treatment was repeated up to 3 times daily. Post insemination treatments were performed for no more than 4 days after ovulation had occurred.Pregnancy diagnosis was performed with ultrasound at 14 to 16 days after ovulation. Scans were then repeated at 30 and 50 days of gestation to confirm the presence in the uterus of an apparently healthy developing conceptus.

Statistical analysis

χ² Analysis was used to determine the effect of reproductive status and age on the incidence of fluid accumulation. In addition, the influence of persistent uterine fluid accumulation on pregnancy rates per cycle was determined for each reproductive class and age by using χ² analysis.

Results

The per-cycle pregnancy rate at 14-16 days after ovulation was 49.3% (245/496 cycles). By the end of the season, 245 of 283 mares (86.5%) were confirmed pregnant. Fluid level of at least 20 mm (grade II or III) was recorded in 126 of the 496 cycles (25.4%). Barren mares had a higher (P < .05) incidence of postbreeding fluid accumulation (64/167; 38.3%) than maiden (34/172; 19.7%) and foaling (28/157, 17.8%; Table 1) mares. The incidence of fluid accumulation was also higher in mares older than 16 years (19/28; 67.8%) than those aged 10 to 16 years (69/244; 28.2%) and 3 to 9 years (38/224; 17%). The incidence of uterine fluid was also higher (P < .05) for mares aged 10 to 16 years than those aged 3 to 9 years (Table 2). Overall, the per-cycle pregnancy rate was lower (P < .05) for mares with post-AI fluid accumulations than for those with no uterine fluid or only a small quantity of fluid (57/126, 41.9% vs 188/360, 56.2%). Pregnancy rates were similar (P > .05) for mares with or without uterine fluid when comparisons were made within maiden and barren mare groups. However, more foaling mares became pregnant when no fluid was detected after insemination. Pregnancy rate for this group (68.1%) was higher than that for maiden (44.2%) and barren (44.6%) mares (Table 3). Older mares with uterine fluid accumulations had a lower per-cycle pregnancy rate (36.8%) than mares in the same group but without fluid. Surprisingly, if no fluid was detected, the highest pregnancy rates were in mares older than 16 years ( Table 4).     

Effect of administration of phenylbutazone or progesterone on recovery of embryos from the uterus of mares 5 days after ovulation.

Twelve horse mares were used to investigate the effect of phenylbutazone or progesterone administration on uterine tubal motility, as reflected by embryo recovery from the uterus on day 5 after ovulation. Four treatment groups were used: group A (controls), in which uterine flush was performed 7 to 11 days after ovulation; group B (5-day controls), in which uterine flush was performed 5 days after ovulation; group C, in which uterine flush was performed 5 days after ovulation following administration of phenylbutazone (2 g, IV) on day 3; and group D, in which uterine flush was performed 5 days after ovulation following administration of progesterone in oil (250 mg, IM) on days 0, 1, and 2. Each mare was randomly assigned to each group once. Embryo recovery for each group was: group A, 13 embryos from 12 mares; group B, 3 embryos from 12 mares; group C, 4 embryos from 11 mares; and group D, 1 embryo from 11 mares. Recovery of embryos on day 5 in 3 of 12 nontreated mares indicated that equine embryos may enter the uterus before day 6. Neither treatment increased embryo recovery from the uterus on day 5 over that from the uterus of the 5-day controls.     

The effects of an advanced uterine environment on embryonic survival in the mare

Reasons for performing the study: During embryo transfer (ET) the equine embryo can tolerate a wide degree of negative asynchrony but positive asynchrony of >2 days usually results in embryonic death. There is still confusion over whether this is due to the inability of the embryo to induce luteostasis or to an inappropriate uterine environment. Objectives: To assess embryo survival and development in an advanced uterine environment. Hypothesis: Embryo–uterine asynchrony, not the embryo's inability to induce luteostasis, is responsible for embryonic death in recipient mares with a >2 days chronologically advanced uterus. Methods: Experiment 1: Thirteen Day 7 embryos were transferred to the uteri of recipient mares with luteal prolongation, occasioned by manual crushing of their own conceptus, such that donor–recipient asynchrony was between +13 and +49 days. Experiment 2: Day 7 embryos were transferred to recipient mares carrying their own conceptus at Days 18 (n = 2), 15 (n = 2), 14 (n = 4), 12 (n = 4) or 11 (n = 4) of gestation. In addition, Day 8 embryos were transferred to 4 pregnant recipient mares on Day 11 of gestation. Results: No pregnancies resulted following transfer of Day 7 embryos to recipients in prolonged dioestrus with asynchronies between +13 and +49 days. However, the use of early pregnant mares as recipients resulted in 5/20 (25%) twin pregnancies, 4 of which came from the transfer of a Day 8 embryo to a Day 11 recipient. All transferred embryos showed retarded growth, with death occurring in 4/5 (80%). Conclusions and potential relevance: The results emphasise the importance of an appropriate uterine environment for embryo growth and the inability of equine embryos to survive transfer to a uterus >2 days advanced even when luteostasis is achieved. It is possible that in normal, non‐ET equine pregnancy, embryo–uterine asynchrony may account for some cases of embryonic death.     

Some Factors Associated With Fertility of Thoroughbred Stallions

The results of 3 years (2005–2007) of observations and mating (5,646 estrous cycles of 3,788 mares bred to 1 of 15 stallions) at one Thoroughbred breeding farm in central Kentucky were analyzed by a multiple logistic regression model using Bayesian statistics to evaluate the relationship between data entries (factors) and pregnancy outcomes. Factors found to be significantly (P < .05) associated with pregnancy outcome included stallion (one stallion had lower OR for pregnancy higher odds ratio [OR] for pregnancy, and one had, than other stallions), date of mating (OR for pregnancy declined slightly in May – July), mare age (OR for pregnancy were higher for mares <13 years old, and lower for mares >18 years old), mare beginning status (foaling mares had a higher OR for pregnancy), mating on foal heat (lowered OR for pregnancy), mating of the day for the stallion (OR for pregnancy was 4.16 times lower for fifth compared with first mating of day), reinforcement breeding (increased OR for pregnancy), dismount semen neutrophil score (lowered OR for pregnancy when neutrophils were present in dismount semen samples), and tranquilization before breeding (lowered OR for pregnancy in foaling and barren mares). The influence of dismount sample sperm motility scores on OR for pregnancy was weak, so motility scores were not included in the final logistic regression model. The majority of variation in pregnancy outcome was because of mare factors, with only approximately one-third of the variation in fertility explained by stallion.     

Assessing the fertility of two mares cloned from the same founder animal

Two cloned mares, produced from the same sample of skin fibroblasts, were bred during four breeding seasons from their second year of age, as embryo donors, in exactly the same conditions, using the same stallions for both cloned mares. The aim of this study was to test the embryo donor potential of cloned mares and to compare the results obtained from two cloned mares of the same mare with other embryo donor mares (n = 31–39 per breeding season) at the same stud. For both cloned mares, 19 embryos were recovered by 43 collection attempts (44%) (7/22 for one; 12/21 for the other), 16 (84%) pregnancies (5/7 for one, 11/12 for the other) were obtained at day 14 post-ovulation (D₁₄), and 12 (3/7 for one; 9/12 for the other) foals were born. One cloned mare was a less efficient donor mare than the other (p < .05), In control donor mares, 623 embryo collections were performed, with a recovery rate (80%—496/623) significantly higher than for cloned mares. The recovery rate in the subpopulation of 2–5-year-old control donor mares (same age of cloned mares) (89%—127/143) and The recovery rate in the subpopulation of 12 control mares bred with the seven same stallions as clones (55%—17/31), were both higher than for cloned mare (p < .05). The success rate of transfer was not different between embryos produced by cloned mares (84%—16/19) and those produced by control donor mares (79%—392/496). However, the foaling rate per embryo collection was significantly lower for cloned mares (28%—12/43) than for control donor mares (52% - 325/623) (p < .05).     

Embryo Transfer in Anovulatory Recipient Mares Treated with Estradiol Benzoate and Long-Acting Progesterone

This study aimed to prepare anovulatory mares in anestrus or in the transitional period as embryo recipients. Ninety embryo-recipient mares were divided into two groups (G). G1 (n = 45) comprised animals in anestrus or in the transitional period; these animals were treated for 3 days (D) with 5, 3, and 2 mg of estradiol benzoate (intramuscular) on D0 (day of the donor's ovulation), D1, and D2 (after ovulation), respectively, followed by weekly application of 400 mg of long-acting progesterone (intramuscular) from D3 after ovulation (donor) until the 120th day of gestation. G2 (n = 45) comprised mares with normal estrous cycles. Plasma levels of progesterone (P₄) were measured on days D1, D2, D8, and D14. Sixty percent of the animals in G1 and 71.1% in G2 (P > .05) completed the pregnancy. On D8, there was no difference in P₄ levels between G1 and G2 animals, but there was a difference in P₄ levels on D14 (P < .05). It was concluded that anovulatory mares in anestrus or in the transitional period could be used as embryo recipients. The protocol was efficient and also considered an appropriate alternative to prepare the uterine environment for embryo transfer; long-acting progesterone administration kept P₄ levels high enough to maintain pregnancy until the 120th day and provided recipients during the time of the year when fewer mares were cycling and ovulating.     

Efficacy of Deslorelin Acetate (SucroMate) on Induction of Ovulation in American Quarter Horse Mares

Equine clinicians rely on ovulation induction agents to provide a timed ovulation in mares for optimal breeding management. Numerous studies have been performed on the efficacy of human chorionic gonadotropin (hCG) to induce ovulation in the mare, but limited clinical data are available for the new deslorelin acetate product SucroMate. This study was designed to evaluate the efficacy of SucroMate (deslorelin) in comparison with hCG to induce ovulation. American Quarter horse mares (n = 256) presented to Colorado State University for breeding management were used in this study. Mares received either deslorelin or hCG when a follicle ≥35 mm was detected by transrectal ultrasound in the presence of uterine edema. Ultrasonographic examinations were subsequently performed once daily until ovulation was detected. Deslorelin was administered to 138 mares during168 estrous cycles, and hCG was given to 118 mares during 136 estrous cycles. Mares administered deslorelin had a similar (P < .05) higher ovulation rate (89.9%) within 48 hours following drug administration than mares administered hCG (82.8%). There are no effects of season or age on ovulation rates in either treatment group. Twenty-one mares administered deslorelin and 11 mares administered hCG were monitored by transrectal ultrasound every 6 hours to detect ovulation as part of a frozen semen management program. Average intervals from deslorelin or hCG administration to ovulation were 41.4 ± 9.4 and 44.4 ± 16.5 hours, respectively. Results of this study indicate that SucroMate is effective at inducing a timed ovulation in the mare.     

Presence of a Temperature Gradient Among Genital Tract Portions and the Thermal Changes Within These Portions Over the Estrous Cycle in Beef Cows

The aim of the present study was to describe the temperature of the different portions of the female genital tract and their relation to rectal temperature and to investigate the effect of steroid hormones profiles on these variables over the estrous cycle in cattle. Four nonpregnant Japanese Black cows were investigated daily over two successive estrous cycles using a digital thermometer with a long probe and rounded-end sensor to record the temperature of the rectum (RT), vagina (VT), cervix (CT), uterine body (UBT) and uterine horns (UHT). Blood samples were collected immediately before temperature recording to assay peripheral levels of progesterone (P₄) and estradiol-17β (E₂). Moreover, transrectal ultrasonography was carried out after temperature recording to monitor the ovulatory follicle and track ovulation. During the experiment, the ambient temperature and relative humidity were recorded for further calculation of the temperature humidity index (THI). The temperature within the genital tracts in these cows progressively increased towards the uterine horns from the vagina. The VT, CT, UBT and UHTs were significantly higher in association with peripheral P₄ concentrations greater than 4 ng/ml (mid-luteal phase) when compared with lower peripheral P₄ concentrations. The VT was more significantly (P<0.01) correlated to the CT, UBT and UHTs than RT. In conclusion, a temperature gradient was present among the vagina, cervix and uterus over the estrous cycle, and changes in peripheral P₄ concentrations were associated with the thermal variations within these portions. The VT could be more beneficial than RT in monitoring temperature of deeper portions of the female genital tract in bovine.     

Elevating the uterus (uteropexy) of five mares by laparoscopically imbricating the mesometrium

Reasons for performing study: There is a need for study of a method for restoring a ventrally positioned uterus to a horizontal position involving fertility of mares with delayed uterine clearance. Hypothesis: A ventrally‐angled uterus can be elevated to a horizontal position using a laparoscopic technique. Objective: To develop a laparoscopic technique of imbricating the mesometria to elevate the uterus to a horizontal position. Methods: The right and left mesometria of 5 pluriparous mares, all barren for 1–8 years (mean 3.8 years), with a pendulous, ventrally‐angled uterus were shortened laparoscopically, by imbrication, with the mares standing, to raise the uterine body and horns to a horizontal position. Sutures were placed through the dorsal aspect of the uterine body and uterine horn and the adjacent region of the mesometrium using a simple continuous suture pattern. Results: The uterus of all 5 mares was elevated successfully to a horizontal position. Three of the mares became pregnant the same year, without other treatment, after the procedure. Conclusions: A pendulous, ventrally‐angled uterus can be returned to a normal, horizontal position by imbricating the mesometria, using a laparoscopic technique. Potential relevance: Elevating a ventrally‐angled uterus to a horizontal position may improve egress of uterine debris, thereby improving fertility.     

Historical Aspects of Equine Embryo Transfer

Early embryo transfer in equids was undertaken simultaneously in the early 1970s in Cambridge, England, and Kyoto, Japan. Both groups achieved limited success when flushing the uterine horn ipsilateral to the side of ovulation but the rates improved markedly when the whole uterus was flushed on realization of the continued movement of the embryo throughout the uterine lumen after day 6. Initial transfers of embryos to recipient mares were carried out surgically, but nonsurgical transfer via the cervix has been used subsequently with increasing success, culminating in pregnancy rates of 75%–90% today. Experimental use of embryo transfer in horses and donkeys demonstrated the unique ability of equids to carry to term a full range of interspecies hybrid conceptuses and extraspecies pregnancies created by embryo transfer. Furthermore, splitting of day 4–8 cell embryos and day 6 compact morulae allowed the creation of genetically identical twin foals. But despite these and other significant advances over the past 45 years, a persisting limitation is the relatively low embryo recovery rates from donor mares treated with exogenous gonadotropins in attempts to induce them to superovulate. This is due to the toughness of the ovarian tunica albuginea which forces ovulation through the ventrally situated ovulation fossa where multiple follicles compete with each other and luteinize before they can ovulate properly.     

Timed artificial insemination in crossbred mares: Reproductive efficiency and costs

Timed artificial insemination (TAI) has boosted the use of conventional artificial insemination (CAI) by employing hormonal protocols to synchronize oestrus and ovulation. This study aimed to evaluate the efficiency of a hormonal protocol for TAI in mares, based on a combination of progesterone releasing intravaginal device (PRID), prostaglandin (PGF_2α) and human chorionic gonadotropin (hCG); and compare financial costs between CAI and TAI. Twenty-one mares were divided into two groups: CAI group (CAIG; n = 6 mares; 17 oestrous cycles) and TAI group (TAIG; n = 15 mares; 15 oestrous cycles). The CAIG was subjected to CAI, involving follicular dynamics and uterine oedema monitoring with ultrasound examinations (US), and administration of hCG (1,600 IU) when the dominant follicle (DF) diameter's ≥35 mm + uterine oedema + cervix opening. The AI was performed with fresh semen (500 × 10⁶ cells), and embryo was recovered on day 8 (D8) after ovulation. In TAI, mares received 1.9 g PRID on D0. On D10, PRID was removed and 6.71 mg dinoprost tromethamine was administered. Ovulation was induced on D14 (1,600 IU of hCG) regardless of the DF diameter's, and AI was performed with fresh semen (500 × 10⁶ cells). On D30 after AI, pregnancy was confirmed by US. The pregnancy rate was 80.0% in TAIG and 82.3% in CAIG (p > .05). The TAI protocol resulted in 65% reduction in professional transport costs, and 40% reduction in material costs. The TAI was as efficient as CAI, provided reduction in costs and handlings, and is recommended in mares.     

Post-partum uterine rupture: Standing repair in three mares using a laparoscopic technique

Three mares underwent diagnostic laparoscopy because of suspicion of post-partum uterine ruptures. All three horses showed clinical signs of a uterine rupture between 1 and 3 days after parturition and underwent diagnostic laparoscopy. In all cases a full thickness uterine rupture could be detected and was sutured laparoscopically. Availability of suture material and surgeon experience were responsible for the surgical methods chosen for repair. In the first case, a hand-assisted laparoscopic approach was chosen for suturing the ruptured uterus, whereas in the other cases the approach was entirely laparoscopic. In the second case, extracorporeal knots were used for the repair and in the last case described a barbed loop suture was available for closure of the uterus. Two of three mares were alive for at least 12 months after surgery without any abdominal problems. One of these mares delivered a healthy foal 2 years after surgery. The remaining mare died 3 months after surgery but no necropsy was done. Laparoscopy should be considered for post-partum mares with signs of peritonitis to access the uterus and repair a rupture if it is accessible. A laparoscopic approach using intracorporeal knots or barbed sutures for the repair of the uterine rupture as well as a hand-assisted laparoscopic approach are feasible. The use of the barbed suture for intracorporeal closure makes the minimal invasive laparoscopic technique easier to perform.     

Twinning in mares: A review of recent studies

Recent studies on twinning are reviewed. Multiple ovulations were more frequent in thoroughbreds (19%) than in quarter horses (9%) and Appaloosas (8%). The multiple ovulation rate was reduced approximately 50% in foaling mares compared to barren and maiden mares. There was a high degree of repeatability of double ovulations and twin pregnancies within mares and within family lines.Only one embryo was found in each of 23 pituitary extract-treated mares with multiple, synchronous ovulations (<2 days apart) and in each of 39 brood-farm mares with double, synchronous ovulations. Pregnancy rates (number of mares pregnant, regardless of number of embryos/mare) were significantly higher for double, synchronous ovulations than for single ovulations in artificially stimulated mares (58% vs 38%) and in brood-farm mares (83% vs 54%). The results indicated that ova produced by synchronous, double ovulations are viable and fertilizable (indicated by the higher pregnancy rates), but that one of the resulting embryos is eliminated (indicated by the absence of twins).Synchronous, double ovulations were not recorded in association with any of 107 sets of natrually occurring twins. Most (76%) of the twin sets were associated with one detected ovulation. The remaining twins were associated either with one ovulation, but a large unovulated follicle was present at the time of the last examination (10%), or with asynchronous, double estrous ovulations (14%). Twins originated more frequently (P < .05) from asynchronous, double estrous ovulations (9/57) than from synchronous, double ovulations (0/39).Approximately 50% of the mares in which twin embryos were diagnosed rectally before day 31, had 1 foal. However, mares in which twins were recorded as present at day 32–36 and day 40–42 had a single foal in only 17% and 6% of the mares, respectively. The methods used for intervention when twins were diagnosed were unsatisfactory. Complete termination of pregnancy with a prostaglandin or intrauterine flushing resulted in failure to establish a singleton pregancy during the remaining breeding season in 10/11 mares. Attempts to eliminate one embryo resulted in loss of both embryos in 6/7 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)     

Clinical experience with deslorelin (ovuplantTM) in a kentucky thoroughbred broodmare practice (1999)

Palpation records of 155 Throughbred broodmares maintained on one of seven farms (3–80 mares per farm) that were administered deslorelin on one or more estrous cycles (204 treated cycles) during the 1999 breeding season were retrospectively examined. Some deslorelin-treated mares were also treated with hCG (2500 units intravenously), or had no ovulation-inducing drugs administered, during different estrous cycles of the same season. Most mares were treated with an ovulation- inducing drug after returning to their resident farm following breeding and were subsequently examined by transrectal ultrasonography daily until ovulation was confirmed, and again 13–14 and 15–16 days after ovulation for determination of pregnancy status.Per-cycle pregnancy rate for all 155 mares bred was 53%, and for all deslorelin breeding was 57%. Per-cycle pregnancy rates for mares ovulating 0–1 days, 1–2 days, and 2–3 days after treatment with deslorelin did not differ (P>0.05). Forty-six mares received more than one treatment during the breeding season, yielding 115 breedings (estrous cycles) for comparison of pregnancy rates among treatment. Per-cycle pregnancy rates for these mares did not differ among treatments (P>0.10).No differences due to treatment were detected in mean interval to ovulation (P>0.10). Mean interovulatory interval was longer for deslorelin-treated mares than for untreated or hCG treated mares (P>0.01). Eighty percent (80%) of deslorelin-treated mares had interovulatory intervals of 18–25 days, and 19% had interovulatory intervals>25 days. Ninety-seven percent (97%) of untreated or hCG-treated mares had interovulatory interovulatory intervals>25 days. More deslorelin-treated mares had extended (>25 days) interovulatory intervals than hCG- or nontreated-mares (P>0.05). In this group of Thoroughbred mares, it appeared that season (month) and management (farm) factors had only minor effects on the incidence of extended interovulatory intervals following use of deslorelin.     

Strategies for Increasing Reproductive Efficiency in a Commercial Embryo Transfer Program With High Performance Donor Mares Under Training

Exercise stress has a negative impact on embryo transfer efficiency (ET). For example, a 34% embryo recovery rate, 43% incidence of poor quality embryos, and a 29% pregnancy rate after transfer have been reported. Administration of nonsteroidal anti-inflammatory drugs (NSAIDs) may reduce the inflammatory response produced after nonsurgical embryo transfer. In addition, progesterone supplementation is commonly administered to some recipient mares to improve uterine conditions before the transfer and to ensure adequate progestational support compatible with pregnancy. The aim of the study was to evaluate embryo recovery rates using BioRelease deslorelin versus hCG and to increase posttransfer pregnancy rates by jointly administering BioRelease progesterone and a NSAID (flunixin or meloxicam) to recipient mares. Seventeen upper-level showjumping mares stabled and in daily training were used as embryo donors. To induce ovulation, 1-mg IM BioRelease deslorelin (BioRelease Technologies, Lexington, KY) was injected in treated cycles (n = 66), or 2500-IU hCG IV (Ovusyn, Syntex, Buenos Aires, Argentina) was given in control cycles (n = 79) when a ≥35 mm follicle was present. Artificial insemination with extended fresh semen (at least 500 × 10⁶ progressively motile sperm) was carried out in both groups immediately after injecting the ovulation induction agent. Day 8 embryos were recovered and nonsurgically transferred using a speculum and a cervical traction forceps. Recipient mares (n = 73) were randomly assigned to one of three groups: Group A received a single injection of 1.5-g IM BioRelease progesterone (Progesterone LA 300, BioRelease Technologies) and 3 IV injections of 0.5 g of flunixin meglumine (Flunix Deltavet, Argentina), one injection administered the day of the transfer and one on each of the next two successive days. Group B received 1.5-g IM BioRelease progesterone and a single dose of 1.5-g IM BioRelease meloxicam (Meloxicam LA, BioRelease Technologies) at the moment of embryo transfer. Group C did not receive any treatment. Pregnancy diagnosis was carried out 7 days after transfer. Results were analyzed using comparisons of proportions. More embryos were recovered per cycle (13% increase) when donor mares in training were induced to ovulate with BioRelease deslorelin (60.6%; 40/66) than with hCG (46.8%; 37 of 79; P < .05). Although both recipient groups given NSAIDs in combination with BioRelease progesterone numerically had higher pregnancy rates (A: 70.8%; 17/24 and B: 75%; 15/20) compared with nontreated control recipients (47.1%; 33/70), pregnancy rates were significantly higher only in recipients given LA meloxicam treatment at the time of transfer (P < .05). The LA meloxicam is released over a 72-hour period making it more practical to use as it requires a single IM injection versus the 3 IV flunixin meglumine injections. Thus, to minimize the effects of exercise stress on ET efficiency, a combination of BioRelease deslorelin to induce ovulation in donors and BioRelease progesterone and LA meloxicam in recipients at the time of transfer may offer an interesting alternative for improving results in commercial ET programs.     

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.