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.     

Use of cloprostenol as an abortifacient in the llama (Lama glama)

As part of a larger project investigating the development and heritability of choanal atresia glama), it was necessary to develop a protocol for aborting llamas at various stages of gestation. Twenty-seven animals between 4 and 7 mo of gestation were successfully aborted a total of 53 times following two 250 microg intramuscular injections of cloprostenol at 24 h intervals. Abortion was induced once in 10 animals and multiple times (range 2 to 5) in 17 animals. Twenty-four animals (45.2%) aborted 3 d following the first injection, with 20 animals (37.7%) aborting 4 d post prostaglandin administration. Other animals aborted at 2 d (n=6, 11.3%), 5 d (n=2, 3.8%), and 7 d (n=1, 1.9%) following drug administration. Forty-nine (92.5%) of the abortions occurred following a single series of injections, while 4 animals (7.5%) aborted following a second series of injections. No confirmed pregnant animals failed to abort following the second series of cloprostenol injections. Conception rates in animals rebred 2 to 4 wk following an abortion were comparable to those of untreated animals in the research herd. Unlike the severe hypertension and death that has been reported following dinoprost tromethamine administration in the llama, no adverse reactions were observed in this study following cloprostenol administration. The results demonstrate that llamas can be safely and effectively aborted up to 7 mo of gestation (normal full term gestation = 342 +/- 10 days) without adverse effects on subsequent fertility.     

Endogenous prostaglandin secretion during cloprostenol-induced abortion in mares

Repeated administration of prostaglandin is the treatment of choice for the termination of pregnancy in mares more than 40 days pregnant. Even though it is well documented that PGF-2 or analogue needs to be administered every 12–24 h for successful induction of abortion, little is known about the underlying endocrine changes and the mechanism by which abortion occurs. The aim of this study was to characterize the changes in PGF-2, progesterone and estrogen secretion during prostaglandin-induced abortion. Six mares, 82–102 days pregnant, were treated daily with 250 μg cloprostenol, blood was collected at 1-h intervals until fetal expulsion and pregnancy examination was performed daily. Four mares, 92–97 days pregnant, received no treatment but were subjected to the same hourly blood collections and daily genital examinations described for cloprostenol-treated mares for 3 days. Mean time from first cloprostenol administration until fetal expulsion was 48.6 ± 5.6 h and required 2.8 ± 0.2 cloprostenol administrations. In all mares, progesterone concentrations decreased in a near linear manner after the first cloprostenol administration and were invariably low (1.3 ± 0.2 ng ml⁻¹, mean ± SEM) at the time of fetal expulsion. Mean estrogen secretion remained unchanged until 5 h before fetal expulsion and then decreased rapidly to non-pregnant levels. Endogenous PGF-2 secretion rate increased with each cloprostenol administration and culminated in sustained PGF-2 secretion which persisted until fetal expulsion was completed. From these results we conclude that cloprostenol-induced abortion is associated with endogenous PGF-2 secretion, fetal expulsion coincides with sustained PGF-2 secretion and low progesterone concentrations and plasma estrogen concentrations remain unchanged until hours before fetal expulsion.     

Short synchronization system for estrus cycles in dairy heifers: a preliminary report

In previous studies we demonstrated that the administration of a luteolytic dose of cloprostenol to dairy cows in luteal phase, followed by hCG plus estradiol benzoate (EB) 12 h later, led to successful timed AI 48 h after the initiation of treatment. This article reports two consecutive studies. In Study 1 we determined the pregnancy rate of dairy heifers in luteal phase (established by palpation per rectum) treated with cloprostenol followed by 250 IU of hCG plus 1 mg of EB 12 h later, and inseminated 48 h after cloprostenol injection. Study 2 was designed to evaluate the efficiency this synchronization protocol, irrespective of the estrus stage of the animals. In Study 1, 1272 Friesian heifers aged 14 to 16 months with a palpable corpus luteum received 500 mcg cloprostenol. Heifers were then synchronized either according to the hCG plus EB protocol (hCG-EB, n=637), or by a second dose of cloprostenol 11 d later (PG, n=636). Animals in this last group served as controls and were inseminated 72 and 96 h after the second cloprostenol injection. The pregnancy rate was significantly higher (P<0.0001) in the hCG-EB group (59.5%, 379/637) than in PG (44.8%, 285/636). In Study 2, 135 contemporary heifers (with no corresponding information on estrus stage) were subjected to the same protocol as those in the hCG-EB group of Study 1. These animals were classified in retrospect according to estrus stage established by plasma progesterone concentration. Pregnancy rates were 66.7% (24/36), 51% (25/49) and 58% (29/50) for animals in the follicular, early/late luteal, and mid-luteal phase, respectively. The total pregnancy rate was 57.8% (78/135). These findings indicate an improved pregnancy rate for heifers subjected to single insemination after cloprostenol/hCG/EB synchronization, compared to double insemination after synchronization by 2 cloprostenol injections 11 d apart. The cloprostenol/hCG/EB protocol did result in acceptable pregnancy rates after timed AI of dairy heifers regardless of their estrus cycle phase.     

Changes in progesterone levels in pregnancy block caused by the proximity of a strange male and by the injection of PMSG

Attempts were made to examine progesterone levels during pregnancy block, first initiated by pheromones and then by the injection of pregnant mare serum gonadotropin (PMSG). The proximity of a strange male inhibits the usual increase in progesterone levels, resulting in no activation of the corpora lutea, from the estrous cycle to the pregnancy. Strain differences were observed in the imitation of pregnancy block by the injection of PMSG. The C3H and BALB/c strains required much smaller doses of PMSG for pregnancy block than the C57BL/6 strain did. The changes of progesterone observed in pregnancy block initiated by PMSG were slightly different from that caused by the proximity of the strange male: The progesterone levels temporally increased on the day following the injection of PMSG and then decreased on day 4 in the PMSG-treated group. These results suggest that PMSG imitates the effect of the proximate strange male in the pregnancy block.     

Termination of unwanted pregnancy in dogs with the dopamine agonist, cabergoline, in combination with a synthetic analog of PGF2alpha, either cloprostenol or alphaprostol

Associations of a dopamine agonist, cabergoline, and a synthetic analog of PGF2alpha, either alphaprostol or cloprostenol, were used to induce pregnancy termination in 15 mature Beagle bitches. Alphaprostol (20 microg/kg/d) was injected subcutaneously (sc) in combination with cabergoline (1.65 microg/kg/d, sc) daily for 5 d from Day 32 after the LH peak in 5 animals. Cloprostenol 2.5 microg/kg/d in one group (n = 5) and 1 microg/kg/d in another group (n = 5) was also used in combination with the same dosage of cabergoline, following the same protocol, but starting from Day 25 after the LH peak. Treatment efficacy, defined by the number of pregnancy terminations, was 100% in all treated groups. Dose-related side effects due to PGF2alpha were observed (excessive salivation, prostration, vomiting, diarrhoea, scratching at the injection site), and were less severe with cloprostenol than with alphaprostol. In the group treated with the lowest dosage of cloprostenol, no adverse reactions were noticed. In all treated groups, interestrus intervals compared with previous cycles and in control animals were reduced after treatment.     

Hypoluteoidism in a bitch

Hypoluteoidism is characterized by insufficient secretion of progesterone by the corpora lutea during pregnancy. The resulting failure to maintain progesterone concentration above a critical level presumably could lead to fetal resorbtion as well as frank abortion. This report concerns a 2.5-year-old Bernese Mountain dog with a history of two previous pregnancies ending in abortion around Day 50 of pregnancy. The bitch was initially presented 2 days after mating. Physical and gynecological examination revealed no abnormalities. The infectious causes of abortion in the bitch, Brucella canis and herpesvirus, were excluded using serology. On Day 26 after mating, ultrasonography confirmed a pregnancy with at least four living fetuses. During the remaining part of the pregnancy repeated transabdominal ultrasonography and plasma progesterone measurements, using a RIA, were performed. On Day 42, ultrasonography revealed living fetuses but plasma progesterone concentration had decreased to 8.3 nmol/L, which is just above the threshold necessary to maintain a vital pregnancy. Oral treatment with 0.1mg medroxyprogesterone acetate (MPA) per kg body weight, once daily, was started and continued until Day 58 in order to prevent abortion due to progesterone deficiency. The endogenous plasma progesterone concentration decreased further, but pregnancy was maintained. On Day 59 a cesarean section was performed because of dystocia and four living and one dead pup were delivered. One puppy had severe facial malformations and was euthanised. The premature decrease in plasma progesterone concentration while ultrasonography demonstrated that the fetuses were still alive, and the maintenance of pregnancy during administration of MPA, strongly support the diagnosis of hypoluteoidism.     

Mid-gestation pregnancy termination by the progesterone antagonist aglepristone in queens

The efficacy of aglepristone, a progesterone receptor antagonist, to induce abortion on days 25 and 26 after first mating was investigated in queens. The cats were divided into two groups: aglepristone (10 mg/kg, subcutaneously) was injected twice, 24 h apart, on days 25 and 26 after first mating, into group I queens (n = 23). Group II queens (n = 6) were not treated and served as controls. Termination of pregnancy and expulsion of the fetuses were successful in 20 (87%) queens in group I. The mean interval between the first administration of aglepristone and the beginning of vaginal discharge was 5+/-1 days (range 4-7 days) and the mean duration of abortion, defined as time span from first occurrence of vaginal discharge to expulsion of all fetuses observed by ultrasonography was 1 day in nine cats, 2 days in five cats and in five cats, less than 1 day. Treatment failed in three queens. In one queen treatment resulted in birth (66 days after mating) of two vital kittens. In another case, three macerated fetuses were found intrauterine without vaginal discharge. In one cat, two fetuses were expulsed and two remained intrauterine and were born 66 days after last mating. All group II queens gave birth to vital kittens after a normal pregnancy length. The mean serum P4 concentrations were similar in treated and control animals. The results indicate that aglepristone treatment at day 25 of pregnancy could induce abortion in 87% of the treated queens. Itching at the site of injection right after injection was the only side effect noticed and only in one queen.     

Termination of mid-gestation pregnancy in bitches with aglepristone, a progesterone receptor antagonist

Six pregnancies were terminated in mid-gestation with aglépristone, a progesterone receptor antagonist, in 5 beagle bitches in order to determine the effects of aglépristone on plasma concentrations of prolactin and progesterone, the duration of the luteal phase, and the interestrous interval. In addition, the effects of aglépristone on the condition of the uterus and fetuses were examined by ultrasonography. After confirmation of pregnancy by ultrasonography, the dogs received 10 mg, s.c. aglépristone per kg body weight on 2 consecutive days at about 30 d post ovulation. Before, during and after treatment with aglépristone, plasma samples were collected for determination of the concentrations of prolactin and progesterone. The condition of the uterus and fetuses was assessed by ultrasonography the day before and at least 3 times a week for at least 2 wk after aglépristone administration. Termination of pregnancy occurred within 4 to 7 d after the start of aglépristone treatment, which was well tolerated, with no side-effects except slight vaginal discharge. The results of ultrasonographic examination indicated that aglépristone leads to abortion but not to fetal resorption. Elevated plasma concentrations of prolactin were observed during aglépristone treatment, while plasma progesterone levels remained unchanged. Pregnancy termination with aglépristone resulted in premature cessation of luteal function. In addition, the interestrous interval was shortened. The latter effects may be the consequence of actions of the progesterone receptor antagonist at the hypothalamus-pituitary level. In conclusion, aglépristone proved to be a safe and effective abortifacient in mid-gestation in the bitch. The results of the present study also indicated that aglépristone directly or indirectly influences pituitary function.     

The effect of cloprostenol in non-pregnant and pregnant Norwegian semi-domestic reindeer (Rangifer tarandus tarandus L)

Two non-pregnant and five pregnant 1.5-year-old semi-domestic reindeer were used to study the effect of cloprostenol given during the luteal phase of the oestrous cycle, or at two stages of pregnancy (early December, n = 3, and mid-January, n = 2). Blood samples were collected at 3-hourly intervals from immediately prior to treatment until 6–8 days after treatment, after which blood samples were collected every second day. Prior to each blood collection, the animals were observed for signs of oestrus. Plasma progesterone, oestradiol-17β, luteinizing hormone (LH) and 15-ketodihydro-PGF_2α were analyzed to characterize variations in ovarian function.Treatment with cloprostenol resulted in an immediate and rapid decrease in plasma progesterone concentrations in all treated animals. The fall in plasma progesterone was associated with increase in 15-ketodihydro-PGF_2α. Oestrus, indicated by standing behaviour, was observed on three out of four occasions in the two non-pregnant animals. The average duration of standing behaviour (oestrus) was 27 h (range: 24–30 h).Of the pregnant females that were treated with cloprostenol in the beginning of December (n = 3), two aborted between 72 and 96 h after treatment. One of these developed pyometra after abortion. In one female the foetus died 2 days after treatment, but was retained within the uterus until slaughter 2.5 months later. One of the two females that were treated in mid-January aborted between 62–65 h after injection. The other female retained a live foetus until slaughter in February. There were few endocrinological differences between animals that aborted and those that did not, though aborting animals had lower progesterone concentrations for a longer period of time after treatment.It was concluded that cloprostenol can be used during the luteal phase of the oestrous cycle to induce luteolysis and oestrus. When given during pregnancy, cloprostenol can induce abortion, though undesired side effects make it inappropriate for practical use.     

Induction of ovulation in gilts with cloprostenol

Prepuberal gilts were treated with 750 IU pregnant mare serum gonadotropin (PMSG) followed 72 h later by 500 IU human chorionic gonadotropin (hCG) to induce follicular growth and ovulation. In this model, ovulation occurred at 42 +/- 2 h post hCG treatment. When 500 mug of cloprostenol was injected at 34 and of 36 h after hCG injection, 78% of the preovulatory follicles ovulated by 38 h compared with 0% in the control gilts. In addition, plasma progesterone concentrations were significantly higher in the cloprostenol-treated group than in the control group (P<0.01) at 38 h, indicating luteinization along with premature ovulation. These results suggest that prostaglandin F(2)alpha (PGF(2)alpha) or an analog can be used to advance, synchronize or induce ovulation in gilts.     

Effect of periovulatory prostaglandin F2alpha on pregnancy rates and luteal function in the mare.

The objective of this study was to determine whether periovulatory treatments with PGF2alpha affects the development of the CL, and whether the treatment was detrimental to the establishment of pregnancy. Reproductively sound mares were assigned randomly to one of the following treatment groups during consecutive estrus cycles: 1. 3,000 IU hCG within 24 hours before artificial insemination and 500 microg cloprostenol (PGF2alpha analogue) on Days 0, 1, and 2 after ovulation (n=8), 2. 2 mL sterile water injection within 24 hours before artificial insemination and 500 microg cloprostenol on Days 0, 1, and 2 after ovulation (n=8); 3. 3,000 IU hCG within 24 hours before artificial insemination and 500 microg cloprostenol on Day 2 after ovulation (n=8); or 4. 3,000 IU hCG within 24 hours before artificial insemination and 2 mL of sterile water on Days 0, 1, and 2 after ovulation (controls; n=8). Blood samples were collected from the jugular vein on Days 0, 1, 2, 5, 8, 11, and 14 after ovulation. Plasma progesterone concentrations were determined by the use of a solid phase 125I radioimmunoassay. All mares were examined for pregnancy by the use of transrectal ultrasonography at 14 days after ovulation. Mares in Group 1 and 2 had lower plasma progesterone concentrations at Day 2 and 5, compared to mares in the control group (P < 0.001). No difference was detected between group 1 and 2. Plasma progesterone concentrations in group 3 were similar to the control group until the day of treatment, but decreased after treatment and were significantly lower than the control group at Day 5 (P < 0.001). Plasma progesterone concentrations increased in all treatment groups after Day 5, and were comparable among all groups at Day 14 after ovulation. Cloprostenol treatment had a significant effect on pregnancy rates (P < 0.01). The pregnancy rate was 12.5% in Group 1, 25% in Group 2, 38% in Group 3, and 62.5% in Group 4. It was concluded that periovulatory treatment with PGF2alpha has a detrimental effect on early luteal function and pregnancy.     

Luteal activity at the onset of a timed insemination protocol affects reproductive outcome in early postpartum dairy cows

This study was designed to compare two timed insemination protocols, in which progesterone, GnRH and PGF2alpha were combined, with the Ovsynch protocol in presynchronized, early postpartum dairy cows. Reproductive performance was also evaluated according to whether cows showed high or low plasma progesterone concentration, at the onset of treatment. One hundred and six early postpartum dairy cows were presynchronized with two cloprostenol treatments given 14 days apart, and then assigned to one of the three treatment groups. Treatments for the synchronization of estrus in all three groups started 7 days after the second cloprostenol injection, which was considered Day 0 of the actual treatment regime. Cows in the control group (Ovsynch, n=30) were treated with GnRH on Day 0, PGF2alpha on Day 7, and were given a second dose of GnRH 32 h later. Cows in group PRID (n=45) were fitted with a progesterone releasing intravaginal device (PRID) for 9 days, and were given GnRH at the time of PRID insertion and PGF2alpha on Day 7. In group PRID/GnRH (n=31), cows received the same treatment as in the PRID group, but were given an additional GnRH injection 36 h after PRID removal. Cows were inseminated 16-20 h after the administration of the second GnRH dose in the Ovsynch group, and 56 h after PRID removal in the PRID and PRID/GnRH groups. Ovulation rate was determined on Day 11 postinsemination by detecting the presence of a corpus luteum in the ovaries. Lactation number, milk production, body condition at the onset of treatment and treatment regime were included as potential factors influencing ovulation and pregnancy after synchronization. Logistic regression analysis for cows with high and low progesterone concentration on treatment Day 0 revealed that none of the factors included in the models, except the interaction between progesterone and treatment regime, influenced the risk of ovulation and pregnancy significantly. In cows with high progesterone concentration at treatment onset, Ovsynch treatment resulted in a significantly improved pregnancy rate over values obtained following PRID or PRID/GnRH treatment. In cows with low progesterone concentration, PRID or PRID/GnRH treatment led to markedly increased ovulation and pregnancy rates with respect to Ovsynch treatment. These findings suggest the importance of establishing ovarian status in early postpartum dairy cows before starting a timed AI protocol, in terms of luteal activity assessed by blood progesterone.     

Effect of prostaglandin F2 alpha at different stages of guinea-pig pregnancy

It is believed that suppression of the processes by which prostaglandin F2 alpha is released from the uterus during the estrous cycle is vital to maintenance of pregnancies in guinea-pigs. Prostaglandin F2 alpha was injected into pregnant guinea-pig at four different stages of gestation to investigate the effect increased prostaglandin might have. The study revealed an alteration in the sensitivity of the pregnancy to prostaglandin F2 alpha as pregnancy progressed. Recovery from the prostaglandin insult was more likely if the injection was given after Day 24 than before Day 18. In some animals the serum progesterone levels fell following the injection and then subsequently recovered. It appears that effects which are potentially hazardous to the pregnancy are countered in a variety of ways.     

Follicular growth, estrus and pregnancy after fixed-time insemination in beef cows treated with intravaginal progesterone inserts and estradiol benzoate

An experiment was performed to compare the effects of 3 short-term treatments with progesterone and estradiol benzoate (EB) on follicular growth, synchrony of estrus and pregnancy rate after fixed-time insemination in lactating postpartum beef cows. In Treatment 1 (n = 46), each cow received a progesterone-containing intravaginal insert for 7 d with injection of EB (2 mg, i.m.) at the time of device insertion. In Treatment 2 (n = 46), the insert was used for only 5 d with injection of EB (2 mg, i.m.) at the time of insertion. Cows in Treatment 3 (n = 47) received an insert for 5 d with no EB at the time of insertion. Each cow in the 3 groups received PGF2 alpha (25 mg, i.m.) at the time of insert removal, followed by EB (1 mg, i.m.) 30 h later. The cows were then inseminated 28 to 30 h after treatment with EB (58 to 60 h after insert removal). Treatment with 2 mg EB terminated the growth of the largest ovarian follicle (> 5 mm in diameter) at device insertion in 16/16 and 14/15 cows in Treatments 1 and 2, respectively. Estrus was detected within an 8-h target period (48 to 56 h after insert removal) in 93, 87 and 81% of cows in Treatments 1, 2 and 3, respectively (P > 0.05). Pregnancy rates at 39 d post insemination were 60, 50 and 51% for Treatments 1, 2 and 3, respectively (P > 0.05). The pregnancy rates did not differ between cows that were anovulatory or those that had ovulated before the initiation of treatments (54%), or among cows that were 28 to 40, 41 to 60 or > 60 days post partum at insemination (43, 59 and 54%, respectively). Treatment with progesterone inserts for 5 or 7 d, PGF2 alpha at the time of insert removal and 1 mg EB 30 h later induced the high degree of synchrony of estrus and ovulation necessary for fixed-time insemination.     

Rates of luteolysis and pregnancy in dairy cows after treatment with cloprostenol or dinoprost

Our objective was to determine whether rates of luteolysis or pregnancy differed in lactating dairy cows of known progesterone status and either known or unknown luteal status after either cloprostenol or dinoprost was injected as part of a timed-insemination program. In Experiment 1, 2358 lactating dairy cows in six herds were given two injections of PGF_2α 14 d apart (Presynch), with the second injection given 12 to 14 d before the onset of a timed AI protocol (Ovsynch). Cows (n = 1094) were inseminated when detected in estrus after the Presynch PGF_2α injections. Cows not inseminated (n = 1264) were enrolled in the Ovsynch protocol and assigned randomly to be treated with either cloprostenol or dinoprost as part of the timed-AI protocol. In cows having pretreatment concentrations of progesterone ≥ 1 ng/mL and potentially having a functional corpus luteum (CL) responsive to cloprostenol (n = 558) or dinoprost (n = 519), dinoprost increased (P < 0.05) luteal regression from 86.6 to 91.3%. Despite a significant increase in luteolysis, pregnancies per AI did not differ between luteolytic agents (dinoprost = 37.8% and cloprostenol = 36.7%). Fertility was improved in cows of both treatments having reduced concentrations of progesterone at 72 h and in cows showing signs of estrus. In Experiment 2, an ovulation-resynchronization program was initiated with GnRH or saline in 427 previously inseminated lactating dairy cows of unknown pregnancy status in one herd. Seven days later, pregnancy was diagnosed and nonpregnant cows were blocked by number of CL and assigned randomly to be treated with cloprostenol or dinoprost. Compared with cloprostenol, dinoprost increased (P < 0.05) luteal regression from 69.1 to 78.5%, regardless of the number of CL present or the total luteal volume per cow. Pregnancies per AI did not differ between dinoprost (32.8%) and cloprostenol (31.3%). Although dinoprost was more effective than cloprostenol at inducing luteolysis in lactating dairy cows exposed to an Ovsynch or ovulation-resynchronization protocol, resulting fertility did not differ between products.     

Determination of early pregnancy and embryonic growth in goats by transrectal ultrasound scanning

Ultrasonography has been shown to be a useful tool for pregnancy diagnosis and the study of embryonic growth in mammals. The objectives of this study were 1) to evaluate the use of real-time B-mode ultrasonography for early pregnancy diagnosis in goats, 2) to define criteria for accurate diagnosis of pregnancy, and 3) to monitor the embryonic growth ultrasonically until Day 40 after mating. Estrus was synchronized in 16 cyclic Anglo-Nubian goats with a single injection of cloprostenol (125 micrograms, i.m.). Estrous females were randomly assigned into 2 groups: 1) goats mated by a vasectomized male (n = 5; MV group), and 2) goats mated by an intact male of proven fertility (n = 11; MF group). Transrectal ultrasonographic examinations with a 5 MHz linear array transducer were performed from Days 13 to 40 post mating. The evaluated parameters included the appearance of nonechogenic areas in the uterus, presence of embryo(s), crown-rump length of embryo and embryonic heart rate (beats/min). On Day 18, the mean (+/- SEM) diameter of nonechogenic areas was 1.5 +/- 0.3 mm in the MV group and 4.0 +/- 0.5 mm in the MF group (P < 0.01). In 36% of the pregnant does these areas were less than 3 mm. The mean (+/- SEM) day of the first detection by means of heartbeats of at least 1 embryo was 20.7 +/- 0.5 d (range, Days 19 to 23). From Days 19 to 38 of pregnancy, crown-rump length was best represented by a linear regression (Y = -2.23 + 0.13X; r2 = 0.94; P < 0.05). Crown-rump length on the day of the first detection of an embryo was 5.3 +/- 0.3 mm, reaching 34.2 +/- 0.6 mm on Day 40. Mean (+/- SEM) heartbeat rate was 168.3 +/- 2.8 beats/min on Day 21, decreasing to 158.3 +/- 2.0 beats/min on Day 40. Detection of the caprine embryo by ultrasonography and confirmation of its viability by heartbeats was shown to be a reliable method for early pregnancy diagnosis in Anglo-Nubian goats. Ultrasonic measurement of crown-rump length was useful in predicting the age of the embryo.     

Pregnancy-specific protein B and progesterone in monitoring viability of the embryo in early pregnancy in the cow after experimental infection with Actinomyces pyogenes

Actinomyces pyogenes can cause embryonic death and abortion during the early stages of pregnancy in cows. Bovine pregnancy-specific protein B (PSPB) is produced in response to a viable embryo and as such it could be a potential marker for embryronic survival. The plasma concentration of PSPB was monitored in cows following an intrauterine infection with A. pyogenes and during the subsequent abortion and recovery from infection. Plasma progesterone concentrations were also monitored, and the results were compared withthose for animals in which abortion had been induced by prostaglandin F2alpha treatment. In abortions induced both by infection and by cloprostenol, the plasma concentration of PSPB fell steadily from the day of treatment, with a half-life of 7 days. In the cloprostenol-induced abortions, progesterone levels fell dramatically to <0.5ng/ml within 24 hours of treatment, while following inoculation with A. pyogenes , progesterone concentration remained elevated for 20 to 40 days and fell to <0.5ng/ml after evacuation of pus from the uterus. Sequential monitoring of PSPB, which identifies embryonic death when a continuing fall in plasma concentration is demonstrated, is a better indicator of embryonic death following bacterial infection with A. pyogenes than plasma progesterone concentration, which falls only when infection is resolved.     

Involvement of endothelin-1 and its receptors in PGF2alpha-induced luteolysis in the rat

The possible mediatory role of endothelin-1 (ET-1) in prostaglandin F(2alpha) (PGF(2alpha))-induced luteolysis in the rat was examined. The effect of PGF(2alpha) was tested on day 9 of pregnancy either in vivo, by injecting cloprostenol, an analog of PGF(2alpha) or in vitro, in isolated intact corpora lutea incubated with PGF(2alpha). Luteolysis was confirmed by progesterone determination in the peripheral blood serum or in the culture medium, respectively. Administration of cloprostenol (.0025 mg/rat) induced within 1 hr, a significant fall (from 56.8 to 27.6 ng/ml, P < 0.0001) in serum progesterone concentrations that was associated with an increased expression of the mRNA to ET-1 and its protein product in rat luteal tissue. Elevated level of ET-1 were also determined at the spontaneous regression of the CL, upon parturition. Expression of the ET receptors, ETA and ETB was not affected by cloprostenol. On the other hand, this PGF(2alpha) analog induced expression of luteal VEGF mRNA. In vitro experiments demonstrate that the LH (100 ng/ml)-induced increase in luteal progesterone secretion was reduced by PGF(2alpha) (1 microg/ml). The inhibitory effect of PGF(2alpha) was reversed by BQ123 (10(- 7) M), that is a selective ETA receptor antagonist. We conclude that the PGF(2alpha)-induced elevation in luteal expression of ET-1 combined with the reversal of its luteolytic effect by an ETA receptor antagonist suggest that ET-1 may take part in the PGF(2alpha)-induced luteolysis in the rat.     

Superovulatory and endocrine responses in holstein heifers treated with either prostaglandin F(2alpha), cloprostenol or fenprostalene

Fifty Holstein heifers were each superovulated three times with FSH-P. At 60 h after the first injection of FSH-P, the animals received either prostaglandin F(2alpha), cloprostenol or fenprostalene in random order. A significant decrease in serum progesterone and a significant increase in serum estradiol-17beta were observed within 24 h of prostaglandin injection, but there were no significant differences among the three treatments. Neither were there any significant differences among the treatments with respect to the frequency of nonresponse to FSH-P treatment, nor the total number of ova/embryos collected between Days 6 and 8 of gestation.