Treatment of Persistent Mating‐Induced Endometritis in Mares with the Non‐Steroid Anti‐Inflammatory Drug Vedaprofen

Recently, successful treatment of mares with a history of persistent mating‐induced endometritis (PMIE) with dexamethasone has been reported. As systemic treatment of horses with glucocorticoids should be handled with caution, we tested the hypothesis that treatment with the non‐steroid anti‐inflammatory drug (NSAID) vedaprofen, an inhibitor of cyclooxygenase‐2, may have comparative, positive effects on fertility. Barren mares with a history of repeated PMIE were treated with vedaprofen (n = 8; initially 2 mg/kg bodyweight followed by 1 mg/kg orally twice daily) from 1 day before the first insemination to 1 day after ovulation or left untreated (n = 9). All mares received oxytocin (20 I.E. s.c.) thrice daily. Uterine swabs were collected for bacteriology and cytology. The day after ovulation, fluid accumulation was detected in three control mares and four treated mares (n.s.). The percentage of neutrophils in uterine cytology was significantly increased in comparison to the day before ovulation irrespective of treatment. Pregnancy was confirmed in two of nine mares in the control group and seven of eight mares in the treatment group (p < 0.05). NSAIDs may positively affect fertility in mares with a history of PMIE.     

Use of a GnRH antagonist,antarelix, associated or not with hCG,to control ovulation in cyclic pony mares

The GnRH antagonist antarelix (Teverelix™) was administered to mares (0.01 mg/kg, i.v., twice a day) during the periovulatory period. In Experiment 1, 20 mares were divided into a treated (A3d−) and a control (Control−) group. A3d− mares received antarelix for 3 days from the day when the dominant follicle (F1) reached 32 mm (D0). In Experiment 2, 10 mares were divided into a treated (A6d+) and a control (Control+) group. A6d+ mares received antarelix for 6 days from D0 and hCG was injected in all animals (1600 IU, i.v.) on D1. Pregnancies were determined 13 days after ovulation. In both experiments, antarelix interrupted or totally abolished the LH surge. In Experiment 1, 5/10 of the A3d− mares (with maximum LH concentrations of 11.6 ng/ml at the beginning of treatment) ovulated at the same time as the Control− mares; the other five mares (with LH concentrations under 5.4 ng/ml) ovulated 13.4±0.6 days later. In Experiment 2, all the A6d+ mares ovulated at the same time as the Control+ mares. In treated mares which ovulated during the treatment, progesterone concentrations and fertility did not differ from control mares. These results demonstrate that in mares: (1) a small elevation of endogenous LH can induce ovulation, (2) ovulation can be postponed approximately 13 days after a 3-day antarelix treatment if initiated just before the preovulatory LH surge, (3) ovulation can be induced by hCG on depressed levels of endogenous LH, (4) the inhibition of the post ovulatory LH surge has no effect either on the corpus luteum or on fertility.     

Effect of a povidone-iodine intrauterine infusion on progesterone levels and endometrial steroid receptor expression in mares

Background

Intrauterine infusions have been widely used for the treatment of endometritis in the mare. Nevertheless, their consequences on endocrine and endometrial molecular aspects are unknown. We studied the effect of a 1% povidone-iodine solution intrauterine infusion on progesterone levels, endometrial histology and estrogen (ERα) and progesterone (PR) receptor distribution by immunohistochemistry.

Methods

Fourteen healthy mares were used in this study. Estruses were synchronized and seven mares were treated with intrauterine infusions at days 0 and 2 post ovulation of two consecutive estrous cycles. Uterine biopsy samples were taken on days 6 and 15 post ovulation.

Results

The treatment did not induce an inflammatory response indicating endometritis, neither affected the ERα. However, it reduced the percentage of PR positive cells (PPC) on day 6 (deep glandular epithelium, control: 95.7 vs. infused: 61.5, P < 0.05). Treated mares tended to have lower progesterone levels on day 2 (3.9 ng/ml vs. 6.6 ng/ml, P = 0.07), and higher levels on day 15 compared with controls (4.4 ng/ml vs. 1.3 ng/ml, P = 0.07).

Conclusion

a 1% povidone-iodine infusion during days 0 and 2 post ovulation in healthy mares did not induce histological changes indicating endometritis, but altered progesterone concentrations and reduced the expression of endometrial PR at day 6 without affecting the ERα. These changes could reduce embryo survival.     

Follicle Diameter and Systemic Hormone Interrelationships during Induction of Follicle Collapse with Intrafollicular Prostaglandin E2 and F2α in Mares

The objectives were to determine: (i) whether intrafollicular administration of PGE2 and PGF2α to mares would hasten follicle collapse and (ii) the differences in reproductive hormone characteristics in mares with spontaneous and prostaglandin‐induced follicle collapses. Six mares were followed for two oestrous cycles each: when the mares reached a follicle diameter of 30–35 mm and showed mild‐to‐moderate endometrial oedema, mares were administered a single 0.5 ml dose containing 500 μg PGE2 and 125 μg PGF2α (treatment cycle) or a placebo (0.5 ml of water for injection; control cycle) into the preovulatory follicle (Hour 0). Blood samples were collected, and serial ultrasound examinations were performed until follicle collapse. Treated mares showed follicle collapse significantly earlier (20.0 ± 5.9 h) than the control mares (72.0 ± 10.7 h). The LH, progesterone, total oestrogens and oestradiol concentrations did not differ between groups; however, the progesterone concentration increased more between 48 and 72 h after follicle injection in the treatment compared to the control cycles (P < 0.05). In conclusion, intrafollicular treatment with PGE2 and PGF2α hastened follicle collapse in mares without the simultaneous use of an inductor of ovulation; despite the early induction of follicle collapse, the profiles of LH and oestradiol were not altered. This study provides information on the role of prostaglandins (PGs) in the process of follicle wall rupture and collapse and suggests that this may happen even before the beginning of the sharp rise in circulating LH at the final stage of the ovulatory surge.     

Plasma progesterone in mares showing oestrus during early pregnancy (author's transl)]

Sixtyfour mares were examined 3 and 6 weeks after mating. Progesterone was measured in 22 mares 3 weeks after mating in order to see if this could be of any help in the oestrous diagnosis. None of the pregnant mares had plasma progesterone below 2 ng/ml. Pregnant mares that did not show oestrus had higher levels of plasma progesterone than pregnant mares showing signs of oestrus 3 weeks after mating. Clinical findings in pregnant and nonpregnant mares 3 weeks after mating is compared, and oestrus in pregnant mares is discussed.     

Changes in LH Pulsatility Profiles in Dairy Heifers During Exposure to Oestrous Urine and Vaginal Mucus

Difficulty in observing oestrus is a problem for many dairy farmers performing AI. Finding ways to synchronize oestrous cycles or strengthen display of oestrus without hormonal treatments would be of great interest because many consumers object to the use of exogenous hormones on healthy animals. Modification of reproductive cycles through chemical communication has been reported in several species including cattle. LH is an important regulator of the follicular phase and could possibly be subject to pheromonal influence. This study focuses on the effect of volatile compounds from oestrous substances on LH pulsatility preceding the preovulatory LH surge in cattle. Four heifers of the Swedish Red breed were kept individually in isolation. Exposure to water during the control cycle (CC), and bovine oestrous urine and vaginal mucus during the treated cycle (TC), started simultaneously with induction of oestrus. Blood sampling at 15‐min intervals started 37 h after administration of PGF_2α and continued for 8 h. Monitoring of reproductive hormones, visual oestrus detection and ultrasonographic examination of the ovaries continued until ovulation had occurred. The mean concentration of LH at pulse nadir was significantly higher during TC (2.04 ± 0.18 ng/ml) than during CC (1.79 ± 0.16 ng/ml), and peak amplitude was significantly higher during CC (Δ1.03 ± 0.09) than during TC (Δ0.87 ± 0.09). No other parameters differed significantly between the two cycles. We conclude that the difference in LH pulsatility pattern may be an effect of exposing heifers to oestrous vaginal mucus and/or urine and that the mechanism behind this needs further investigation.     

Peri-oestrus hormone profiles and follicle growth in lactating sows with oestrus induced by intermittent suckling.

This study describes follicle dynamics, endocrine profiles in multiparous sows with lactational oestrus compared with conventionally weaned sows (C). Lactational oestrus was induced by Intermittent Suckling (IS) with separation of sows and piglets for either 12 consecutive hours per day (IS12, n = 14) or twice per day for 6 h per occasion (IS6, n = 13) from day 14 of lactation onwards. Control sows (n = 23) were weaned at day 21 of lactation. Pre-ovulatory follicles (> or =6 mm) were observed in 100% of IS12, 92% of IS6 and 26% of C sows before day 21 of lactation and in the remaining 74% C sows within 7 days after weaning. All sows with pre-ovulatory follicles showed oestrus, but not all sows showed ovulation. Four IS6 sows and one IS12 sow developed cystic follicles of which two IS6 sows partially ovulated. Follicle growth, ovulation rate and time of ovulation were similar. E(2) levels tended to be higher in IS sows (p = 0.06), the pre-ovulatory LH surge tended to be lower in IS12 (5.1 +/- 1.7 ng/ml) than in C sows (8.4 +/- 5.0 ng/ml; p = 0.08) and P(4) levels were lower in IS12 and IS6 than in C sows (at 75 h after ovulation: 8.8 +/- 2.4 ng/ml vs 7.0 +/- 1.4 ng/ml vs 17.1 +/- 4.4 ng/ml; p < 0.01). In conclusion, sows with lactational oestrus induced by IS are similar to weaned sows in the timing of oestrus, early follicle development and ovulation rates, but the pre-ovulatory LH surge and post-ovulatory P(4) increase are lower.     

The post-ovulatory rise in progesterone is lower and the persistence of oestrous behaviour longer during the first compared with the second cycle of the breeding season in mares

Mares are seasonally polyoestrous breeders. Therefore, the first ovulation of the season, following winter anoestrus, is the only cycle in which mares ovulate without the presence of an old CL from the previous cycle. The objective of this study was to compare the length of oestrous behaviour, and plasma progesterone concentrations during the early post-ovulatory period between mares after the first and second ovulation of the breeding season. Overall, 38 mares and 167 oestrous periods were used in the study. From those, 11 mares were used during the first and subsequent oestrous period to measure and compare the post-ovulatory rise in progesterone concentration, whereas all the mares were used to compare the length of the post-ovulatory oestrous behaviour between the first and subsequent cycles of the breeding season. The persistence of the post-ovulatory oestrus was longer (p < .001) following the first ovulation of the year (median of 52 h) compared with the subsequent ovulations (median of 36 h for second and later ovulations groups; n = 38 mares). The progesterone concentration at any of the four 8 h-intervals analysed (28, 36, 76 and 84 h post-ovulation) was lower (p < .01) following the first versus the second ovulation of the year. By 36 h post-ovulation the progesterone concentration of mares at the second ovulation of the year had passed the threshold of 2 ng/ml (2.1 ± 0.33 ng/ml), whereas in the first cycle it was 1.2 ± 0.13 ng/ml. In conclusion, mares had lower progesterone concentrations in their peripheral circulation and longer persistence of oestrous behaviour following the first ovulation of the year compared with the second and subsequent ovulatory periods of the breeding season.     

Changes of serum anti‐Müllerian hormone in a mare with granulosa cell tumour following surgery and reinitiation of follicular activity

Anti‐Müllerian hormone (AMH) has been reported to be elevated in mares with granulosa cell tumour (GCT). An 8‐year‐old Thoroughbred mare was presented for not being observed in oestrus after the beginning of the breeding season. Rectal palpation and ultrasonography revealed enlargement and cystic appearance of the left ovary while the right ovary was small with an anoestrous‐like appearance. The AMH concentration was 694.9 ng/ml. Presumptively diagnosed with GCT, the mare was subjected to tumour removal. Histopathology confirmed GCT. To evaluate changes of AMH concentration following surgery, blood samples were collected immediately prior to surgery, and on Days 1, 2, 4, 8, 16 and 32 after surgery. Thereafter, blood samples were collected monthly and also at the time the mare was observed in oestrus (148 days after tumour removal). The AMH concentrations decreased over the first 2 months after surgery (from 721.2 ng/ml to 0.1 ng/ml). Subsequently, AMH concentration increased and peaked at the time of oestrus expression (0.7 ng/ml). The mare then became anoestrous, and AMH concentration decreased and reached 0.2 ng/ml, which was not significantly different from the mean concentration of AMH in normal anoestrous mares (n = 5; 0.26 ± 0.07 ng/ml). In conclusion, the present report implies the potential use of AMH for determination of the time of follicular resumption in mares after GCT removal.     

hCG‐Induced Ovulation in Thoroughbred Mares Does Not Affect Corpus luteum Development and Function During Early Pregnancy

Our aim was to compare Corpus luteum (CL) development and blood plasma concentration of progesterone ([P₄]) in thoroughbred mares after spontaneous (Control: C) or human chorionic gonadotrophin (hCG)‐induced ovulation. Lactating mares (C = 12; hCG = 21) were daily teased and mated during second oestrus post‐partum. Treated mares received 2500 IU hCG i.v. at first day of behavioural oestrus when dominant follicular size was >35, ≤42 mm and mated 12–24 h after. Control mares in oestrus were mated with dominant follicular size ≥45 mm. Dominant follicle before ovulation, CL and gestational sac were measured by ultrasound and [P₄] by radioimmunoassay (RIA). Blood sampling and ultrasound CL exams were done at days 1, 2, 3, 4, 8, 12, 16, 20, 25, 30, 35, 40, 45, 60 and 90 after ovulation and gestational sac from day 12 after ovulation in pregnant (P) mares; non‐pregnant (NP) were followed until oestrus returned. Data analyses considered four subgroups: hCG‐P, hCG‐NP, C‐P and C‐NP. Preovulatory follicular size was smaller in hCG mares than in C: 39.2 ± 2.7 mm vs 51.0 ± 1.8 mm (p < 0.0001). All hCG mares ovulated 24–48 h after treatment and presented similar oestrus duration as controls. C. luteum size in P mares showed the same pattern of development through days 4–35, presenting erratic differences during initial establishment. Thus, on days 1 and 3, CL was smaller in hCG‐P (p < 0.05); while in hCG‐NP, CL size was greater than in C‐NP on day three (p = 0.03). Corpus luteum size remained stable until day 90 in hCG‐P mares, while in C‐P a transient and apparently not functional increase was detected on days 40 and 45 (p < 0.05) and the decrease from day 60 onwards, made this difference to disappear. No differences were observed in [P₄] pattern between P, or between NP subgroups, respectively. So, hCG‐induced ovulation does not affect CL development, neither [P₄] during early pregnancy. One cycle pregnancy rate tended to be lower in hCG mares while season pregnancy rates were similar to controls.     

Plasma LH, Ovulation and Conception Rates in Cats Mated Once or Three Times on Different Days of Oestrus

Although cats are induced ovulators, the relationship between the day of breeding, the number of matings and the likelihood of ovulation and conception have not been extensively investigated. In this experiment, cats were mated either once or three times on day 1 or day 5 of oestrus to study the incidence of the LH surge, ovulation and conception rates. The percentage ovulating and the conception rates after a single mating on day 1 of oestrus were 60% (6/10) and 33.3% (2/6), respectively, and for cats mated once on day 5 of oestrus were 83.3% (10/12) and 40% (4/10), respectively. When cats were mated three times on day 1 of oestrus, the ovulation rates and conception rates were 70% (7/10) and 85.7% (6/7), respectively, and for those mated three times on day 5 of oestrus were 100% (10/10) and 100% (10/10), respectively. The concentration of LH did not increase in non-ovulating cats, and cats that were mated three times had LH concentrations that were numerically higher than those that were mated once. Litter size was neither related to the day of mating nor to the number of matings. Although an increase in the number of matings on day 1 of oestrus produced a numerically larger LH surge, it did not increase the ovulation rate, suggesting that plasma oestradiol concentrations were not sufficiently elevated to induce a high pituitary response to mating stimulation. The conception rate after a single mating was low, suggesting that the number of sperm per mating was not sufficient. These results suggest that mating more than once in the middle of oestrus is required to improve ovulation rates and conception rates in cats.     

雌酮主动免疫对美利奴母羊发情产羔和生殖内分泌的影响

20头母羊在配种季节开始前6周和3周,用雌酮免疫原免疫2次(E组),13头不作处理为对照(C组)。免疫不影响母羊正常发情,可使母羊产羔率由115.38％提高到156.25％,发情当天的LH水平显著提高(3.06±0.61对1.93±0.88miu/ml);发情周期黄体期的孕酮水平亦增加,周期12天时差异显著(9.31±3.53对3.71±0.92ng/ml);整个发情周期内E组的睾酮水平显著高于C组,而17β-雌二醇水平两组间无差异。     

Effect of the administration of PGF2 alpha synchronously with insemination on the pregnancy rate in mares in an insemination program

Investigations in different species including the horse have demonstrated that prostaglandin F2 alpha (PGF2 alpha) is involved in initiating uterine contractions occurring during mating and artificial insemination (A.I.). Uterine contractions play an important role with respect to the sperm transport within the female genital tract. The objective of the present investigation was to evaluate whether the administration of PGF2 alpha (Dinoprost) synchronously to A.I. could have a positive effect on the pregnancy rate in mares. A field study including 346 warmblood-mares (age two to 20 years) belonging to a private studfarm was conducted during the breeding season 1996. The mares were assigned to two groups, group A: mares with spontaneous ovulation, group B: mares in which the ovulation was induced by a GnRH-analog-implant (Deslorelin). PGF2 alpha (Dinoprost) was administered either intramusculary (i.m., 5.0 mg) or intrauterine (i.ut., 0.5 mg diluted in 1.9 ml isotonic NaCl-solution and added to the semen dosis). The study was carried out in a double-blind fashion using isotonic NaCl-solution as a placebo. The mares of each group were randomly assigned to one of the two treatments (i.m. vs. i.ut.). The following first cycle pregnancy rates (day 18) were obtained in mares treated and inseminated once per oestrus: group A1 (PGF2 alpha, i.m.): 54.5% (n = 33); group A2 (placebo, i.m.): 69.7% (n = 33); group A3 (PGF2 alpha, i.ut.): 65.4% (n = 26); group A4 (placebo, i.ut.): 69.8% (n = 32); group B1 (PGF2 alpha, i.m.): 56.5% (n = 46); group B2 (placebo, i.m.): 29.6% (n = 27); group B3 (PGF2 alpha, i.ut.): 66.7% (n = 45); group B4 (placebo, i.ut.): 60.0% (n = 30). The pregnancy rates did not differ between the different groups with the exception of group B2 (p < 0.05). In mares treated repeatedly during the oestrus period (group A, n = 88; group B, n = 23), the pregnancy rates did not differ significantly between treatment and control groups. From the results obtained it is concluded that the PGF2 alpha-application did not show an effect on the pregnancy rate. Further factors influencing the results to a small degree were the stallions, semen age and quality and frequency of insemination per oestrus.     

The effect of pulsatile gonadotropin-releasing hormone and estradiol administration on luteinizing hormone and follicle-stimulating hormone concentrations in pituitary stalk-sectioned ovariectomized pony mares

Hourly pulses of gonadotropin-releasing hormone (GnRH) or bi-daily injections of estradiol (E2) can increase luteinizing hormone (LH) secretion in ovariectomized, anestrous pony mares. However, the site (pituitary versus hypothalamus) of positive feedback of estradiol on gonadotropin secretion has not been described in mares. Thus, one of our objectives involved investigating the feedback of estradiol on the pituitary. The second objective consisted of determining if hourly pulses of GnRH could re-establish physiological LH and FSH concentrations after pituitary stalk-section (PSS), and the third objective was to describe the declining time trends of LH and FSH secretion after PSS. During summer months, ovariectomized pony mares were divided into three groups: Group 1 (control, n = 2), Group 2 (pulsatile GnRH (25 μg/hr), n = 3), and Group 3 (estradiol (5 mg/12 hr), n = 3). All mares were stalk-sectioned and treatment begun immediately after stalk-section. Blood samples were collected every 30 min for 8 h on the day before surgery (DO) and 5 d post surgery (D5) to facilitate the comparison of gonadotropin levels before and after pituitary stalk-section. Additionally, jugular blood samples were collected every 12 hr beginning the evening of surgery, allowing for evaluation of the gonadotropin secretory time trends over the 10 d of treatment. On Day 10, animals were euthanized to confirm pituitary stalk-section and to submit tissue for messenger RNA analysis (parallel study). Plasma samples were assayed for LH and FSH by RIA. Mean LH secretion decreased from Day 0 to Day 5 in Groups 1 and 3, whereas LH secretion tended (P < 0.08) to decrease in Group 2 mares. On Day 5, LH was higher (P < 0.01) in Group 2 (17.26 ± 3.68 ng/ml; LSMEANS ± SEM), than either Group 1 (2.65 ± 4.64 ng/ml) or group 3 (4.28 ± 3.68 ng/ml). Group 1 did not differ from Group 3 on Day 5 (P < 0.40). Similarly, mean FSH levels decreased in all groups after surgery, yet Group 2 mares had significantly (P < 0.001) higher FSH concentrations (17.66 ± 1.53 ng/ml) than Group 1 or Group 3 (8.34 ± 1.84 and 7.69 ± 1. 63 ng/ml, respectively). Regression analysis of bi-daily LH and FSH levels indicated that the time trends were not parallel. These findings indicate: 1) Pituitary stalk-section lowered LH and FSH to undetectable levels within 5 d after surgery, 2) pulsatile administration of GnRH (25 μg/hr) maintained LH and FSH secretion, although concentrations tended to be lower than on Day 0, and 3) E2 did not stimulate LH or FSH secretion.     

Comparison of Different Treatments for Oestrous Induction in Seasonally Anovulatory Mares

The aim of this study was to evaluate the effects of different treatments for induction and synchronization of oestrus and ovulation in seasonally anovulatory mares. Fifteen mares formed the control group (C), while 26 mares were randomly assigned to three treatment groups. Group T1 (n = 11) were treated with oral altrenogest (0.044 mg/kg; Regumate^®) during 11 days. Group T2 (n = 7) was intravaginally treated with 1.38 g of progesterone (CIDR^®) for 11 days. In group T3 (n = 8), mares were also treated with CIDR^®, but only for 8 days. All mares received PGF2α 1 day after finishing the treatment. Sonographic evaluation of follicles, pre‐ovulatory follicle size and ovulation time was recorded. Progesterone and leptin levels were analysed. Results show that pre‐ovulatory follicles were developed after the treatment in 88.5% of mares. However, the pre‐ovulatory follicle growth was dispersal, and sometimes it was detected when treatment was not finished. While in mares treated with intravaginal device, the follicle was soon detected (1.5 ± 1.2 days and 2.3 ± 2.0 days in T2 and T3 groups, respectively), in T1 group, the pre‐ovulatory follicle was detected slightly later (3.9 ± 1.6 days). The interval from the end of treatment to ovulation did not show significant differences between groups (T1 = 13.1 ± 2.5 days; T2 = 11.0 ± 3.6 days; T3 = 13.8 ± 4.3 days). The pregnancy rate was 47.4%, similar to the rate observed in group C (46.7%; p > 0.05). Initial leptin concentrations were significantly higher in mares, which restart their ovarian activity after treatments, suggesting a role in the reproduction mechanisms in mares. It could be concluded that the used treatments may be effective for oestrous induction in mares during the late phase of the seasonally anovulatory period. Furthermore, they cannot synchronize oestrus, and then, it is necessary to know the reproductive status of mares when these treatments are used for oestrous synchronization.     

The Effect of Sulpiride Treatment During the Periovulatory Period on Prolactin Concentration and Ovulation in the Mare

Sixteen estrous cycles from 10 cyclic mares were randomly assigned to a control or sulpiride group (n = 8 each). All mares received 1,500 IU of human chorionic gonadotropin (hCG) (hour 0) during estrus with a follicular diameter ≥32 mm. Mares were scanned every 12 hours until ovulation. In the treatment group, beginning at hour 0, each mare received 1.5 mg/kg of sulpiride every 12 hours intra-muscularly until ovulation or formation of a luteinized unruptured follicle (LUF). Concentrations of luteinizing hormone (LH) and prolactin (PRL) were measured by radioimmunoassay. In each group, there were 10 preovulatory follicles for the eight cycles. The ovulation rate (9/10, 90%) was similar in the control and sulpiride groups. Two mares formed an LUF, which was first detected at hours 48 and 72 for the sulpiride and control mares, respectively. The interval from hCG to ovulation was 49.5 ± 11.1 and 43.5 ± 5.8 hours, for the control and sulpiride groups, respectively (P > .5). LH followed the typical preovulatory surge pattern, with no difference between groups (P > .5). Sulpiride administration increased PRL concentration in treated mares at 24 (P < .1), 36, and 48 hours (P < .05) after treatment. In conclusion, sulpiride administration every 12 hours increased PRL concentration in treated mares after 24 hours of the beginning of treatment. However, at this time window and concentration, PRL did not have any effect on ovulation. The control mare that developed an LUF had a PRL concentration similar to other ovulatory control mares (always ≤10 ng/mL).     

Oestrous Behaviour and Timing of Ovulation in Relation to Onset of Oestrus and LH Peak in Mithun (Bos frontalis) Cows

The objectives of the study were to evaluate the oestrus behaviour and to determine the timing of ovulation in relation to onset of oestrus and the pre-ovulatory LH surge in mithun (Bos frontalis). For this purpose, the blood samples collected at 15-min intervals for 9 h period following onset of oestrus and thereafter, at an interval of 2 h till 4 h post-ovulation for three consecutive cycles from 12 mithun cows were assayed for plasma LH and progesterone. Ovulation was confirmed by palpation of ovaries per rectum at hourly intervals. Various signs of behavioural oestrus were also recorded. The common signs of oestrus and their frequency of occurrence in mithuns were following and mounting by male mithuns (100%), standing to be mounted (100%), frequent urination (62.33%), raising of tail (65.23%), swelling of vulva (54.26%) and congestion of vulvar mucous membrane (69.87%). The pre-ovulatory LH surges consisted of several pulses (2.92 +/- 0.26 pulses/animal; range, 1-4). The mean (+/-SEM) peak level of LH for individual mithun varied from 6.99 +/- 0.44 to 12.69 +/- 2.10 ng/ml and the mean pooled LH peak concentration was 9.10 +/- 0.60 ng/ml. The highest peak (highest amplitude of LH during LH surge) was 10.83 +/- 0.76 ng/ml (range, 8.07-16.49 ng/ml). The duration of LH surge was 6.98 +/- 0.22 h (6-8 h). Onset of LH surge was at 1.23 +/- 0.17 h post-oestrus onset (range, 0.25-2.25 h). Mean plasma progesterone stayed low (<0.24 ng/ml) during the entire duration of sampling. Ovulation occurred at 26.92 +/- 0.31 (range, 26-29 h) after the onset of oestrus and 18.63 +/- 0.35 h (range, 17-20.75 h) after the end of LH surge. The occurrence of the highest LH peaks within a narrow time frame of 2- to 5-h post-oestrus onset in mithuns could have contributed to the animals ovulating within a narrow time interval. These results are very promising from a practical standpoint of potential success when AI program in this species is implemented in a big way. Furthermore, the results of the occurrence of LH pulses during pre-ovulatory LH surges, which are required for ovulation in this species of animals, is unique and species specific.     

Melengestrol acetate as a tool for inducing early ovulation in transitional mares

The efficacy of melengestrol acetate (MGA) to shorten the vernal transition of mares by synchronising and accelerating the first ovulation of the year after 60 days of phototherapy was determined by ultrasonographic monitoring. Sixteen mares in late transition were fed two doses of MGA (150 mg/mare/day and 100 mg/mare/day, respectively) for 10 days. A luteolytic dose of prostaglandin was administered to each mare one day after the end of MGA treatment. The presence and duration of oestrus, follicular growth, uterine oedema and presence of ovulation were monitored by ultrasonography and the cervical tone was evaluated by rectal palpation. Ovulation was detected in 87.5% of the mares treated with 150 mg MGA/mare/day for 10 days, and in 62.5% of the mares receiving 100 mg MGA/mare/day for 10 days. This was statistically different (P = 0.03) from the untreated control mares having an ovulation rate of 20%. Mares that received 150 mg MGA/day for 10 days had a mean treatment to ovulation interval of 13.1 +/- 5.97 days after the end of treatment, while mares that received 100 mg MGA/day for 10 days had a mean of 25.6 +/- 10.50 days (P = 0.01) to ovulation. These results suggest that MGA can be used for synchronising and hastening the first ovulation of the year in mares.     

Effect of repeated administration of oxytocin during diestrus on duration of function of corpora lutea in mares

OBJECTIVE: To determine whether IM administration of exogenous oxytocin twice daily on days 7 to 14 after ovulation blocks luteolysis and causes prolonged function of corpora lutea (CL) in mares. DESIGN: Prospective study. ANIMALS: 12 mares. PROCEDURES: Beginning on the day of ovulation (day 0), jugular blood samples were collected every other day until day 40 for determination of progesterone concentration. On day 7, mares (n = 6/group) were treated with saline (0.9% NaCl) solution (control group) or oxytocin. Beginning on day 7, control mares received 3 mL of sterile saline solution every 12 hours, IM, and oxytocin-treated mares received 60 units of oxytocin every 12 hours, IM, through day 14. Mares were considered to have prolonged CL function if progesterone concentration remained > 1.0 ng/mL continuously through day 30. RESULTS: The proportion of mares with prolonged CL function was significantly higher in the oxytocin-treated group (6/6), compared with the control group (0/6). All control mares underwent luteolysis by day 16, at which time their progesterone concentrations were < 1.0 ng/mL. In contrast, all 6 oxytocin-treated mares maintained progesterone concentrations > 1.0 ng/mL continuously through day 30. CONCLUSIONS AND CLINICAL RELEVANCE: IM administration of 60 units of oxytocin twice daily on days 7 to 14 after ovulation was an efficacious method of inhibiting luteolysis and extending CL function in mares. Disrupting luteolysis by administering exogenous oxytocin during diestrus appears to be a plausible and practical method of long-term suppression of estrus in mares.     

Use of a Mycobacterial Cell Wall Extract (MCWE) in Susceptible Mares to Clear Experimentally Induced Endometritis With Streptococcus zooepidemicus

The ability of an immunomodulator, mycobacterial cell wall extract (MCWE), to clear uterine infection in susceptible mares after an experimental challenge withStreptococcus zooepidemicus was evaluated. Thirty mares susceptible to endometritis, based on the presence of uterine fluid during both diestrus and estrus, were selected from a herd of 896 and inoculated with a live culture of 5 × 10⁶ CFU of S. zooepidemicus on day 1 of estrus. Twenty-four hours later, mares were evaluated by ultrasonography, bacteriology, exfoliative cytology, and uterine biopsy to confirm infection. Forty-eight hours after inoculation, and on confirmation of uterine infection, mares were randomly assigned to one of four unbalanced experimental treatments to receive 1500 μg MCWE IU (n = 10) or IV (n = 10), or placebo IU (n = 5) or IV (n = 5). Mares were examined at ovulation and 7 days post-ovulation for uterine fluid via transrectal ultrasonography and for bacteriology, exfoliative cytology, and uterine biopsy. Efficacy was based on the ability of the mare to clear endometritis as determined by negative bacteriology and reduced numbers of polymorphonuclear cells (PMNs) on uterine biopsy. Because no statistical difference was detected between routes of administration on day 7 post-ovulation, the data sets were combined and re-analyzed to evaluate overall efficacy. Endometritis was observed in all placebo-treated mares 7 days post-ovulation, whereas treatment with MCWE resulted in the elimination of endometritis in 35% of the mares by the time of ovulation, and 70% of the mares by 7 days post-ovulation. Treatment with MCWE, compared with the placebo group, resulted in a significant decrease in the number of mares positive for endometritis at ovulation based on exfoliative cytology and bacteriology (P < .01) and at 7 days post-ovulation based on biopsy, exfoliative cytology, and bacteriology (P < .001). Results indicate that MCWE was an effective treatment for the elimination of endometritis caused by S. zooepidemicus in mares.