The effect of postpartum uterine lavage on foal heat pregnancy rate

Mares (n = 37) were treated on Days 2 and 4 post partum with a uterine lavage of 10 l of warm, sterile NaCl (0.9%) solution. Endometrial cytology and culture were performed on Day 7. Mares were bred on the first postpartum estrus by artificial insemination. Pregnancy rates were determined by ultrasound examination at Day 16 post ovulation. No differences were noted in degree of uterine inflammation or presence of uterine bacteria at Day 7 post partum between treated (n = 18) and control (n = 19) mares. Pregnancy rates at the first postpartum estrus for treated mares (55.5%) was not statistically different from that of control mares (68.4%). No advantage was noted in the use of intrauterine lavage with 10 l of warm sterile NaCl (0.9%) at Days 2 and 4 post partum as a means of improving foal heat pregnancy rate.     

Induction of ovulation during the postpartum period in the thoroughbred mare with a prostaglandin analogue,Synchrocept™

Breeding of mares at the foal heat is desirable, but the low pregnancy rate and the not infrequent occurrence of subsequent anestrus are a deterrent. A PGF_2a analogue, Synchrocept^? (prostalene), as a single 2 mg subcutaneous injection was used to induce ovulation, either during the corpus luteum phase subsequent to a foal heat (test group 1) or at a fixed interval of 20 days from parturition (test group 2) in mares that also had a foal heat. Mares with no signs of a foal heat were treated 20 days postpartum (test group 3). A total of 80, mostly Thoroughbred, mares were treated in more than 15 breeding centers in Northern Germany between mid-January and mid-May 1975. At the same locations and over the same time periods, 60 control mares (control group 1) were bred at the foal heat and 40 additional control mares (control group 2) were bred later than 25 days postpartum.In groups 1 and 2, treatment induced estrus in 95% of the mares and in group 3 estrus was induced in 68% of the mares. Of these animals, 92% were bred and 81% conceived on the average 28 days after parturition. The number of services per conception in mares treated was 25% lower (2.5) than in controls (3.2). Synchrocept acted as a luteolysin, but seems also to have induced heat and estrus in animals with plasma progesterone levels below 1 ng/ml, as has been reported previously. Neither mares nor foals showed detectable clinical signs of drug intolerance.     

Influence of day of postpartum breeding on pregnancy rate, pregnancy loss rate, and foaling rate in Thoroughbred mares

Records (years 2005-2007) were analyzed from a Thoroughbred stud farm in central Kentucky. Data from all breeding cycles of foaling mares were tabulated (3184 cycles of 2003 foaling mares bred between 7 and 163 days postpartum). A multiple logistic regression model employing Bayesian statistics was used to adjust for factors that significantly affected outcome; odds ratios (ORs) for pregnancy rate, pregnancy loss rate, and foaling rate were determined to examine the influence of day of postpartum breeding on these parameters. Mares bred before Day 22 (Day 0 = day of foaling) postpartum had a decreased OR for becoming pregnant (P < 0.05); the median OR for becoming pregnant (1.00) was not reached until Day 46 postpartum. Mares bred before Day 13 postpartum had an increased OR for pregnancy loss (P < 0.05). The median OR for pregnancy loss did not decline below 1.00 until Day 78 postpartum. Mares bred before Day 20 postpartum had a decreased OR for producing a foal (P < 0.05). The median OR for producing a foal (1.00) was not reached until Day 75 postpartum. We concluded that fertility (in terms of a higher OR for becoming pregnant and a lower OR for pregnancy loss, resulting in a higher OR for producing a foal) continued to improve in Thoroughbred mares for approximately 2.5 mo postpartum. These findings are of importance to management strategies directed at early postpartum breeding, and explain some of the reported drift in subsequent foaling dates of Thoroughbred mares, despite management practices that employ early postpartum breeding.     

Control of estrus in the lactating postpartum mare with fluprostenol (ICI-81,008)

During the 1976 breeding season 68 mares (56 Thoroughbred and 12 Quarter Horse) were allotted to 4 treatment groups. On day 7, 8 or 9 post-ovulation or day 6, 7 or 8 after foal heat each of 28 mares was injected intramuscularly with 250 μg of the prostaglandin analogue ICI-81,008 (generic name fluprostenol). In the second group, 32 mares were bred at foal heat. Group 3 consisted of 9 mares, which were passed at foal heat and bred at the second postpartum estrus. In group four, 12 of the mares which had failed to conceive at foal heat were bred at the second estrus. Twenty-four prostaglandin treated mares returned to estrus 4.2±.4 days post-injection. The interestrual interval was shorter (P<.05) for prostaglandin treated mares (11.4±.6 days) than for previously mated second heat control mares (19.2±2.3). Also, the interval between parturition and second estrus was decreased (P<.05) in treated mares (24.5±.8 days) compared to group three (32.8±2.5 days). Duration of the second postpartum estrus was similar for both treated and control mares. Plasma progesterone levels in prostaglandin treated mares as determined by RIA were 7.5±.5 and 6.9±.5 ng/ml before treatment and at l hour post-injection, then dropped precipitously to near undetectable levels at 48 hours after injection. Pregnancy rate at 45 days was significantly higher (P<.05) in prostaglandin treated mares (78%) as compared to foal heat mares (48%) and mares which were passed at foal heat and bred at the second postpartum estrus (44%).     

Reproductive function of mares given daily injections of prostaglandin F2alpha beginning at day 42 of pregnancy

Mares at Day 42 of pregnancy received daily intramuscular (i.m.) injection of 5 mg of prostaglandin F2alpha (PGF(2alpha)) until the beginning of the first (Group I, n = 3) or second estrous cycle (Group II, n = 2). All mares aborted 3 to 4 d after the first injection; they displayed estrus 2 to 6 d after this injection. As determined by palpation per rectum and serum progesterone levels, each estrus was accompanied by an ovulation. Endometrial cups did not regress after PGF(2alpha) treatment since serum samples from the mares contained pregnant mare serum gonadotropin (PMSG) for at least 30 d after first injection, as determined by mare immunopregnancy test. After the first estrus, two of three mares in Group I displayed a prolonged diestrus (> 25 d). In contrast, the first estrous cycle was short (8 to 12 d) for mares in Group II. Serum progesterone levels in the first 6 d postovulation were lower (P < 0.05) for Group II than for Group I, indicating that formation of the corpus luteum was impaired by daily injections of PGF(2). Results indicate that 1) daily injections of PGF(2alpha) can induce abortion in mares at Day 42 of pregnancy, 2) abortion is followed by estrus and ovulation, 3) the endometrial cups do not regress as a result of this treatment, and 4) daily injections of PGF(2) can impair early corpus luteum development.     

Spontaneous and oxytocin-induced uterine motility in cyclic and postpartum mares

Intrauterine pressure was measured in three cyclic and two postpartum mares. Pressure was recorded using a catheter tip pressure transducer. The transducer was passed transcervically into the uterus.. In cyclic mares recordings were started on Day 1 of estrus and continued daily until ovulation as well as on Days 1 and 8 of diestrus. In postpartum mares recordings were started within 48 h after foaling and continued until the mares ovulated. The intrauterine pressure changes in postpartum mares was also recorded on Days 1 and 8 of diestrus. Spontaneous uterine contractions were recorded in cyclic mares for 30 min and in postpartum mares for 10 min. Induced uterine motilities were recorded for 30 min in both groups after the administration of oxytocin (40 USP, i.v.). Total area under the contraction curve in a 10-min period was used as a uterine motility quantitating unit. All mares demonstrated uterine contractions during estrus and diestrus. All mares demonstrated significant responses to oxytocin during estrus and diestrus. It appears that estrogen priming is not necessary for a significant uterine response to oxytocin.     

Uterine involution, day and variance of first postpartum ovulation in mares treated with progesterone and estradiol-17beta for 1 or 2 days postpartum

The effects of a single or double regimen of exogenous progesterone and estradiol-17beta (P/E, total dose 300 mg P/20 mg E) were investigated in 50 postparturient Quarter Horse mares. In Trial 1, at 1 and 24 h after foaling, mares were injected with progesterone (150 mg) and estradiol-17beta (10 mg) (n = 7) or 0.9% NaCl (control, n = 13). In Trial 2, within 12 h after foaling, mares were injected with progesterone (300 mg) and estradiol-17beta (20 mg) (n = 13) or 0.9% NaCl (control, n = 17). Mares were examined daily by palpation per rectum and transrectal ultrasonography to determine the day of ovulation. The largest cross sectional diameters of each uterine horn and uterine body were measured ultrasonographically on Day 15 postpartum. Mean uterine diameters did not differ between treatment groups (P > 0.05) in Trial 1, Trial 2 or for combined data for both Trials 1 and 2. For mares bred on the first postpartum estrus pregnancy rates did not differ (P > 0.05) between treatment groups (16/18, 89%) and controls (22/30, 81%) nor was there a difference in mean day to first postpartum ovulation (P > 0.05) between treated and control groups in Trial 1, Trial 2 or Trials 1 and 2 combined. However, fewer (P < 0.05) total P/E treated mares (0/20) ovulated prior to Day 10 postpartum than did control mares (6/30). Variance in days to ovulation was lower (P < 0.05) for P/E treated mares (var = 3.73 days) than for control mares (var = 7.64 days) for data combined from Trials 1 and 2.     

Factors affecting the incidence of postpartum oestrus, ovarian activity and reproductive performance in Thoroughbred mares bred at foal heat under Indian subtropical conditions

Decreased reproductive performance due to summer stress is a well known phenomenon in farm livestock. Whether this occurs in the mare and specifically how this might affect postpartum reproductive activity and performance, especially at Foal Heat (FH), is unknown. This study, therefore, aims to investigate this and the factors that might affect postpartum reproductive activity. Reproductive records of 228 Thoroughbred mares (694 mare years) bred in subtropical north-western India were retrospectively analysed. Overt oestrous activity occurred within 21 d postpartum in 92.94% (645/694) of mares. Significantly (p < 0.001) more April foaling mares (97.37%, 185/190) expressed postpartum oestrous activity than those foaling in January (83.61%; 51/61) and February (88.49; 123/139). Similarly significantly (p < 0.01) fewer multiparous mares failed to demonstrate oestrous activity than primiparous mares (6.12% vs.15.07%; 38/621 vs. 11/73, respectively). 190 of these 694 mares were additionally monitored to confirm ovulation; in these mares onset of FH (oestrus plus confirmed ovulation) occurred 8.42 ± 0.17 d and first ovulation 13.64 ± 0.20 d postpartum. Month, stud farm, year, and parity did not affect interval from parturition to FH onset or to first ovulation; or FH onset to ovulation. In FH bred mares Day 16 pregnancy rate and overall foaling rate were 53.76% (100/186) and 46.24% (86/186) respectively and were similar to those of mares bred later postpartum. FH pregnancy rates were not affected by stud, season, month, year, number of matings, or day of ovulation but were significantly (p < 0.008) lowered by increasing mare age. Significantly (p < 0.01) lower Day 16 pregnancy rates were observed in uterine treated mares compared to untreated mares (31.09% vs. 57.96%; 9/29 vs. 91/157, respectively), this difference was not evident during the rest of pregnancy. In conclusion, postpartum reproductive and ovarian activity appears to be affected by environment, i.e., delayed in subtropical kept Thoroughbred mares compared to those kept in temperate climates. However, resulting reproductive performance at FH and the factors affecting postpartum reproductive activity are similar.     

The effect of the gonadotrophin-releasing hormone analog, buserelin, administered in diestrus on pregnancy rates and pregnancy failure in mares

Two trials involving 578 mares were performed to investigate the effect of a single intramuscular treatment of 40 microg buserelin, an analog of gonadotrophin releasing hormone, on pregnancy rate in mares. All mares were bred by natural mating and were allocated into pairs One mare in each pair was injected with buserelin either on Day 10 or 11 (Trial 1) or on Days 8 to 10 (Trial 2) after ovulation. Pregnancy status of mares was determined by transrectal ultrasonographic examination on Day 14 or 15 after the day of ovulation and was repeated between Days 28 and 30 of pregnancy. In Trial 1, buserelin treatment increased the pregnancy rate at Days 14 and 15 (72.5 vs 66.6%, P < 0.01). At the second pregnancy examination, pregnancy losses were lower in the treated group of mares (4.1 vs 7.4%; P < 0.05). In Trial 2, buserelin also improved the pregnancy rate (57.2 vs 53 5%; P < 0.05) at Days 14 and 15 Pregnancy losses between the first and second examinations were lower in the treated group of mares (6.5 vs 12.0%; P < 0.05). Buserelin increased pregnancy rates after breeding at the first estrus in both trials. In addition, buserelin treatment increased the pregnancy maintenance rate at Days 28 to 30.     

Biodegradable estradiol microspheres do not affect uterine involution or characteristics of postpartum estrus in mares

Quarterhorse mares were used to investigate effects of estradiol-17beta on uterine involution, duration of estrus, interval to ovulation, and fertility achieved by breeding on the first postpartum estrus. On the day of foaling, mares were injected with biodegradable poly (DL-lactide) microspheres containing either 100 mg estradiol-17beta (25 mares) or no drug (27 mares). The treatment period was considered to last for 12 to 15 d. Estrus was determined by teasing mares (n=16) with a stallion. Ovulation was detected by transrectal ultrasonographic examination of ovaries (n=48). On Days 6, 11 and 16 post partum, transrectal ultrasonography was used to measure cross-sectional diameters of the uterine body, uterine horns, and fluid within the uterine lumen (n=28). Uteri were swabbed for bacteriologic culture, and uterine biopsies were obtained from the previously gravid uterine horn on Days 11 and 16 post partum, for assessment of endometritis and morphometric analysis of endometrial histioarchitecture (n=19). Twenty-two mares were bred on foal-heat, and pregnancy was determined by transrectal ultrasonography on 14 to 16 and 30 to 35 d after breeding. With only one exception (diameter of previously gravid uterine horn on Day 11), mean values for all measures of uterine involution did not differ between treatment groups (P > 0.05). No differences were detected between treatment group means for length of estrus or interval to ovulation (P > 0.05). No differences were detected between treatment group liklihoods for recovery of potential bacterial pathogens, presence of endometritis, or presence of intrauterine fluid at 11 or 16 d post partum (P > 0.05). Pregnancy rate of mares treated with estradiol (5 11 ; 45%) was not different from that of control mares (9 11 ; 82%; P > 0.05). Estradiol treatment did not hasten uterine involution, increase duration of estrus, delay ovulation, or increase fertility in these postpartum mares.     

Management and fertility of mares bred with frozen semen.

Semen quality, mare status and mare management during estrus will have the greatest impact on pregnancy rates when breeding mares with frozen semen. If semen quality is not optimal, mare selection and reproductive management are crucial in determining the outcome. In addition to mare selection, client communication is a key factor in a frozen semen program. Old maiden mares and problem mares should be monitored for normal cyclicity and all, except young maidens, should have at least a uterine culture and cytology performed. Mares with positive bacterial cultures and cytologies should be treated at least three consecutive days when in estrus with the proper antibiotic. With frozen semen, timing the ovulation is highly desirable in order to reduce the interval between breeding and ovulation. The use of ovulation inducing agents such as human chorionic gonadotropin (hCG) or the GnRH analogue, deslorelin, are critical components to accurately time the insemination with frozen semen. Most hCG treated mares ovulate 48h post-treatment (12-72h) while most deslorelin (Ovuplant) treated mares ovulate 36-42h post-treatment. However, mares bred more than once during the breeding cycle appear to have a slight but consistent increase in pregnancy rate compared to mares bred only once pre- or post-ovulation. In addition, the "capacitation-like" changes inflicted on the sperm during the process of freezing and thawing appear to be responsible for the shorter longevity of cryopreserved sperm. Therefore, breeding closer to ovulation should increase the fertility for most stallions with frozen semen. Recent evidence would suggest that breeding close to the uterotubal junction increases the sperm numbers in the oviduct increasing the chances of pregnancy. Post-breeding examinations aid in determining ovulation and uterine fluid accumulations so that post-breeding therapies can be instituted if needed. Average pregnancy rates per cycle of mares bred with frozen semen are between 30 and 40% with a wide range between sires. Stallion and mare status are major factors in determining the success of frozen semen inseminations. Pregnancy rates are lower for barren and old maiden mares as well as those mares treated for uterine infections during the same cycle of the insemination. To maximize fertility with frozen semen, a careful selection of the stallions and mares, with proper client communication is critical. Dedication and commitment of mare owner and inseminator will have the most significant impact on the pregnancy rates.     

Effects of deslorelin or hCG administration on reproductive performance in first postpartum estrus mares

A tendency for deslorelin implants to suppress subsequent follicular growth and delay return to estrus following induced ovulation has been documented in nonlactating mares. To investigate this phenomenon in lactating mares, 22 broodmares in southeast Texas were administered either deslorelin or hCG to induce ovulation in the first postpartum estrus during February and March 2001. Mares were teased daily and examined twice weekly (Tuesdays and Thursdays) by transrectal ultrasonography. When a follicle >35 mm diameter was detected on Tuesday, mares were treated with either 2,500 U hCG administered intravenously or with one implant (2.1 mg) deslorelin administered subcutaneously. Mares were bred every other day until ovulation was detected or until they ceased behavioral estrus, and were examined 16 days after treatment to detect pregnancy. Follicular measurements were recorded for all mares during each examination, and interestrous intervals were recorded for mares not becoming pregnant. Treatment of mares with either hCG or deslorelin resulted in similar ovulatory responses and pregnancy rates. Deslorelin-treated mares had fewer ovarian follicles >20 mm in diameter 16 days after treatment than hCG-treated mares (P < 0.01). Interestrous intervals for mares failing to become pregnant on foal heat breeding were prolonged in deslorelin-treated compared to hCG-treated mares (P < 0.01). Date of treatment was negatively correlated with length of the interestrous interval in deslorelin-treated mares (P < 0.01), but was not correlated with length of interestrous interval in hCG-treated mares (P > 0.10). All mares failing to become pregnant from foal heat breedings became pregnant from later breedings, but the parturition to conception interval was prolonged in deslorelin-treated compared to hCG-treated mares that did not become pregnant on foal heat (P < 0.01).     

The effect of oxytocin and PGF2alpha on the uterine involution and pregnancy rates in postpartum Arabian mares

In this study, the effects of oxytocin and an analog of prostaglandin (cloprostenol) on the uterine involution and pregnancy rates were investigated. Mares received 3 ml of 0.9% NaCl in Group C (n=10), 30 IU/mare of oxytocin in Group O (n=10) and 250 microg/mare of cloprostenol in Group P (n=10) within 12h after parturition. The gravid uterine horn's cross-sectional diameter was measured by ultrasonography. The mean uterine diameters did not differ significantly between the treatment (O and P) and the control (C) groups (p>0.05). The difference between the postpartum ovulation periods (Group C: 12.6+/-0.72 days, Group O: 15+/-1.33 days, Group P: 14.6+/-1.11 days), the pregnancy rates at foal heat (Group C: 60%, Group O: 60%, Group P: 80%) and the embryonic death rates at foal heat (Group C: 33.3%, Group O: 16%, Group P: 25%) were not found to be statistically significant between the treatment and the control groups. The mean progesterone concentrations were similar in all groups and decreased continuously from parturition to until foal heat (Group C: from 2.43+/-0.24 to 0.66 ng/ml, Group O: from 3.07+/-0.6 to 0.27+/-0.27 ng/ml and Group P: from 2.8+/-0.44 to 0 ng/ml) (p>0.05). In conclusion, it was decided that the oxytocin and PGF2alpha treatments performed on the mares with the purpose of stimulating involution had no effect on the duration of parturition-first ovulation, the shrinkage of the uterus diameter, the pregnancy and embryonic death rates.     

Effects of different artificial insemination techniques and sperm doses on fertility of normal mares and mares with abnormal reproductive history

The effects of different artificial insemination (AI) techniques and sperm doses on pregnancy rates of normal Hanoverian breed mares and mares with a history of barrenness or pregnancy failure using fresh or frozen-thawed sperm were investigated. The material included 187 normal mares (148 foaling and 39 young maiden mares) and 85 problem mares with abnormal reproductive history. Mares were randomly allotted into groups with respect to AI technique (routine AI into the uterine body, transrectally controlled deep intracornual AI ipsilateral to the preovulatory follicle, or hysteroscopic AI onto the uterotubal junction ipsilateral to the preovulatory follicle), storage method of semen (fresh, frozen-thawed), AI volume (0.5, 2, 12 ml), and sperm dose (50 x 10(6) or 300 x 10(6) progressively motile sperm (pms) for fresh semen and 100 or 800 x 10(6) frozen-thawed sperm with >35% post-thaw motility). The mares were inseminated once per cycle, 24 h after hCG administration when fresh semen was used, or 30 h for frozen-thawed semen. Differences in pregnancy rates between treatment groups were analyzed by Chi-squared test, and for most relevant factors (insemination technique, mare, semen, and stallion) expectation values and confidence intervals were calculated using multivariate logistic models. Neither insemination technique, volume, sperm dose, nor mare or stallion had significant effects (P > 0.05) on fertility. Type of semen, breeding mares during foal heat, and an interaction between insemination technique, semen parameters, and mares did have significant effects (P < 0.05). In problem mares, frozen semen AI yielded significantly lower pregnancy rates than fresh semen AI (16/43, 37.2% versus 25/42, 59.5%), but this was not the case in normal mares. In normal mares, hysteroscopic AI with fresh semen gave significantly (P < 0.05) better pregnancy rates than uterine body AI (27/38, 71% versus 18/38, 47.3%), whereas in problem mares this resulted in significantly lower pregnancy rates than uterine body AI (5/15, 33.3% versus 16/19, 84.2%). Our results demonstrate that for problem mares, conventional insemination into the uterine body appears to be superior to hysteroscopic insemination and in normal mares, the highest pregnancy rates can be expected by hysteroscopic insemination.     

Efficacy of a prostaglandin analogue in reproduction in the cycling mare.

A prostaglandin F analogue caused luteolysis in normal cycling non-lactating mares, and lactating mares (treated after the foal estrus). Effective doses ranged from 1.0 to 4.0mg given as a single subcutaneous injection 8–10 days after ovulation. A dose of 0.5mg was ineffective, hence the dose-response relationship was steep, indicative of a quantal type of response. Mares usually returned to estrus within 2–4 days and ovulated by 7 days after treatment. Mares bred naturally or by artificial insemination at the induced estrus and ovulation were fertile. The compound was without side-effects, and hence should be of value in manipulating the estrous cycle of the mare.     

Periparturient events in ovariectomized embryo transfer recipient mares

Ovariectomized mares treated with progesterone have established and maintained pregnancy after embryo transfer. This study evaluated the ability of ovariectomized embryo transfer recipients to successfully undergo parturition, raise a foal, and return to a useful reproductive status. Periparturient events in three ovariectomized embryo transfer recipient mares and three intact mares were compared. All mares foaled normally. Mammary scores were similar for both groups and all mares produced sufficient colostrum and milk to allow normal growth of healthy foals. Plasma progesterone levels decreased to < 5 ng/ml by Day 4 post partum in both groups. Progesterone concentrations continued to decrease and remained at <1 ng/ml in ovariectomized mares, but increased after the first postpartum ovulation (Day 9 to 15) in intact mares. Endometrial involution as determined by histological evaluation was complete in ovariectomized mares by Day 10 post partum and in intact mares by Day 11 post partum. As assessed by palpation per rectum and clearance of bacteria from the uterus, uterine involution was similar in all mares. The three ovariectomized mares subsequently received embryos by transcervical transfer and two of them established pregnancy. These results indicate that normal parturition, lactation, maternal behavior and uterine involution are independent of ovarian function.     

Hastened transport of equine embryos through the oviduct of the mare

The purposes of this experiment were 1) to test the hypothesis that placing rabbit embryos into the mare's uterus would hasten oviduct transport and 2) to determine if placing fluid into the uterus of bred mares on Day 4 and/or Day 5 would subsequently disrupt the mare's pregnancy. The hypothesis that placing rabbit embryos into the mare's uterus would hasten oviduct transport was not supported, since the uterine recovery rate of equine embryos on Day 5 was not significantly higher (P>0.05) for mares receiving rabbit embryos on Day 4 than for mares receiving no uterine infusion on Day 4 (1 10 vs 0 10 , respectively). However, placing fluid into the mare's uterus on Day 4 was apparently responsible for hastened oviduct transport, since mares with media infused into the uterus on Day 4 had a significantly higher (P<0.05) recovery rate of equine embryos on Day 5 than did mares receiving either rabbit embryos or no uterine infusion on Day 4 post ovulation (5 10 vs 1 10 or 0 10 , respectively). The Day-14 pregnancy rate was significantly higher (P<0.05) for mares receiving no uterine infusion on Day 4 or Day 5 than for mares receiving uterine infusion on Day 5 or uterine infusion on both Days 4 and 5 (9 10 vs 4 10 , 2 10 and 0 10 , respectively).     

Comparison of equine pituitary extract and follicle stimulating hormone for superovulating mares

Sixty light-horse, nonlactating mares were used to compare the efficacy of equine pituitary extract versus follicle stimulating hormone (FSH-P) for inducing multiple ovulations. On Day 12 of diestrus, mares were assigned to receive 1) no treatment, controls; 2) subcutaneous injections of 750 Fevold rat units of equine pituitary extract once daily; or 3) intramuscular injection of 150 mg of FSH-P twice daily. Ultrasound was used twice daily to visualize follicular changes and ovulation. For mares in Groups 2 and 3, treatment was initiated when two or more follicles > 20 mm were detected, and it continued until all large follicles (> 30 mm) had ovulated or regressed. Five milligrams of prostaglandin F(2)alpha (PGF(2)) were administered to mares in Groups 2 and 3 on the first day of treatment. Human chorionic gonadotropin (3,300 IU) was given to all groups of mares during estrus when a 35-mm follicle was detected. Ovulation rate was greater (P < 0.05) for mares treated with pituitary extract (2.2) compared to FSH-P treatment (1.6) or no treatment (1.0). Thirteen of 18 mares treated with the extract had more than one ovulation versus only four of nine FSH-treated mares. Mares in the pituitary extract group were given injections for an average of 6.4 d compared to 6.8 d (13.7 injections) for FSH-treated mares. Intervals to estrus and ovulation from initial injection of extract were 2.9, 7.6; and 2.6, 9.2 d for FSH-treated mares. The mean number of medium-sized follicles (25 to 30 mm) was greater (P < 0.05) in extract-treated mares compared to the FSH-treated mares. Both extract and FSH increased (P < 0.05) the number of follicles > 30 mm and the size of the second largest follicle 1 and 2 d prior to ovulation when compared to controls. Overall, mares with multiple ovulations had more (P < 0.05) follicles 25 to 30 mm and > 30 mm on Day -6 through -1 (Day 0 = day of ovulation) than single ovulating mares. Those mares that had multiple ovulations had less (P < 0.05) size difference between the largest and second largest follicle when compared to single ovulating mares. In summary, FSH-P at the one dose studied was less effective than equine pituitary extract in inducing follicular activity and multiple ovulation in the mare.     

Effects of synchronization and frequency in insemination on fertility.

Fifty-four normally cycling, non-lactating mares were given 2 injections (i.m.) of PGF-2 alpha (10 mg) 14 days apart without regard to stage of the oestrous cycle. At 19 days after the first PGF-2 alpha treatment, a single i.m. injection of either hCG (3300 i.u.) or a GnRH-analogue (500 micrograms) was administered. Each mare was inseminated with 100 X 10(6) motile spermatozoa at one of the following frequencies: once only on Day 20; every other day during oestrus or at least on Days 19 and 21; or daily during oestrus or at least on Days 19, 20, 21 and 22. Eighteen control mares received saline injections on Days 0 and 14, and were inseminated either on the 4th day of oestrus or every other day or daily beginning on the 2nd day of oestrus. More (P greater than 0.05) PGF-2 alpha treated mares displayed their 1st day of oestrus on Days 14 to 20 than control mares (80.6 versus 27.8%). During cycle 1, fewer (P greater than 0.05) treated mares became pregnant compared to controls; 38.9, 25.0 and 66.7% for PGF-2 alpha + hCG, PGF-2 alpha + GnRH-A and control mares, respectively. After three cycles, the pregnancy rates for mares inseminated every other day or daily were higher (P less than 0.05) than mares inseminated only once during oestrus (88.9 and 88.2 versus 64.7%).     

The effect of postbreeding uterine lavage on pregnancy rate in mares

One stallion and 54 mares were used in an experiment to evaluate the effect of postbreeding uterine lavage on pregnancy rate in mares. All mares were inseminated with 250 x 10(6) progressively motile sperm every other day during estrus until detection of ovulation. Mares (n = 18) were randomly assigned to one of three treatment groups: 1) no postbreeding uterine lavage (control); 2) uterine lavage at 0.5 h postbreeding; or 3) uterine lavage at 2 h postbreeding. A dilute solution of povidone-iodine (PIS; 0.05%) previously determined to render spermatozoa immotile in vitro was used to lavage the mare uteri. One liter PIS, prewarmed to 40 degrees C, was used for each lavage. Pregnancy status of mares was determined at 21 d and 36 d post ovulation, using transrectal ultrasonography. The pregnancy rate of Group 1 (66.7%) was higher than that of Group 2 (22.2%; P<0.05) or Group 3 (33.3%); P<0.10). The pregnancy rates of Groups 2 and 3 were similar (P>0.70). Evaluation of endometrial biopsies obtained from a separate set of mares (n = 3) on Day 6 post ovulation, both before and after uterine lavage, revealed no difference in the accumulation of inflammatory cells, suggesting adverse effects of lavage on fertility may have been due to excessive removal of spermatozoa from the uterus during the lavage process or damage to oviductal spermatozoa.