Luteal function of induced corpora lutea in the bitch

Nineteen anestrous bitches with a mean of 22 kg body weight and ranging from 2 to 4 years of age were induced to exhibit estrus and ovulate using PMSG and HCG. Twelve days after the first day of estrus, bitches were assigned to four treatment groups. Group (A) consisted of six bitches, Group (B) of five bitches and Groups (C) and (D) of four bitches each. At this time, bitches in Groups (A), (B) and (C) were laparotomized and those assigned to Groups (A) and (B) were bilaterally hysterectomized leaving the cervix and oviducts intact. Although bitches in Group (C) were laparotomized, they were not hysterectomized. Group (D) bitches were not subjected to any surgical procedures. Homologous uterine extract was prepared from each bitch in Group (A) and administered intramuscularly beginning on day 25 (day 0 = first day of estrus) and continued every other day for 61 days post-estrus. Bitches in Group (B) were similarly injected with equal volumes of 0.9% saline. Blood samples, obtained prior to laparotomy and every other day for 85 days thereafter, were assayed for plasma progesterone concentrations using radioimmunoassay. One bitch in each of Groups (A) and (D) did not form luteal tissue following treatment with PMSG and HCG although both bitches exhibited estrus following treatment. All other bitches showed an increase in progesterone levels (4 to 19 ng/ml) between the first day of estrus and 10 days post-estrus. Thereafter, progesterone levels progressively declined in all groups with levels below 1 ng/ml between 38 to 40 days post-estrus. Results of this study suggested that CL formed in the bitch following PMSG and HCG treatment have a reduced function compared to non-induced CL of a normal, non-fertile estrous cycle. Such premature CL regression appears to be independent of the presence or absence of the uterus.     

Progesterone secretion by induced corpora lutea (CL) of anestrous bitches after administration of gonadotropin-releasing hormone (GnRH) and human chorionic gonadotropin (HOG)

Sixteen bitches were treated with pregnant mare serum gonadotropin (PMSG; 44 IU/kg bwt) intramuscularly (i.m.) for nine consecutive days and each was given 500 IU HOG i.m. on the tenth day or on the first day of induced estrus (Day 0). On Day 12, each bitch was randomly assigned to three groups and treated as follows: Group 1-six bitches, each given 10 mcg GnRH i.m.once every 24 hr; Group 2-six bitches, each given 500 IU HOG i.m. once every 24 hr; and Group 3-four bitches, each given 5 ml 0.9% saline i.m. once every 24 hr. Treatments were continued until Day 55. Blood samples were obtained prior to treatment and every other day until Day 55. Plasma progesterone concentrations were determined by radioimmunoassay (RIA) and data arranged using a split-plot design, with treatment as the main plot and days of sampling as subplots. Analysis of data was by Duncan's Multiple Range Test and treatment-by-day interaction determined by the least-squares method. After treatment, progesterone concentrations from Group 2 were higher (P<0.05) than those of the other groups. A significant effect was seen on Day 20 (P<0.01), while on Day 50 the difference approached significance. These findings suggest that HOG is capable of stimulating the production of progesterone by induced CL in the bitch. However, neither HOG nor GnRH prevented premature regression of these induced CL. Results of this study suggest that premature luteolysis of induced CL is probably not due to lack of gonadotrophic support from either the hypothalamus or the anterior pituitary gland.     

Luteal function in the hysterectomized bitch following treatment with prostaglandin F2α (PGF2α)

Estrus and ovulation were induced in ten mature, mixed-breed, anestrous bitches (10 to 20 kg) using exogenous gonadotropins. Bitches were bred once, on the second day of estrus. Between 11 and 13 days following estrus, bitches were bilaterally hysterectomized and randomly divided into two treatment groups of five bitches each. Four days following surgery, Group A (treated) was given a single subcutaneous injection of PGF₂α (Prostin F₂ alpha^®) at a dose of 1 mg/kg body weight and Group B (controls) similarly given an equal volume of .9% saline. Blood samples were collected daily by cephalic venipuncture prior to surgery and for 75 days thereafter. Plasma progesterone was monitored by a radioimmunoassay method. Although bitches were teased daily following PGF₂α or saline treatments, estrual behavior was not exhibited. In both the PGF₂α and saline treatment groups, plasma progesterone levels showed a transient decline by 12 hours following injection, although a more dramatic decrease was observed at this time in the prostaglandin-treated bitches. Subsequently, progesterone concentrations tended to increase in both groups at 6 days following treatment, however, not to pre-treatment levels. Within 20 to 32 days following treatment in both groups, plasma progesterone levels declined to <1 ng/ml and remained depressed at least 60 days post-injection. In this study, complete luteal regression was not induced following PGF₂α treatment. Luteal function in both groups, as indicated by plasma progesterone concentrations, was shortened in the absence of the uterus.     

Fertile estrus induced in bitches by bromocryptine, a dopamine agonist: a clinical trial

The dopamine agonist bromocryptine, probably through amplifying gonadotroph (mainly FSH) secretion, was found to be suitable for provoking fertile estrus during the anestrous phase in bitches without functional cycles and/or ovarian activity. We studied estrus induction in 48 bitches after treatment with semisynthetic ergot alkaloid bromocryptine. For habituation a fractional dose of 0.3 mg/bitch was administered for three days followed by larger doses within the range of 0.6 to 2.5 mg/bitch by selecting dose rates on the basis of individual responsiveness and body weight. The long-term daily bromocryptine dose did not exceed 0.6 mg/bitch and 2.5 mg/bitch in small and large sized bitches, respectively. Gradual habituation and individual dose rates have almost completely eliminated the unwanted side effect of emesis. The period between treatment and onset of estrus varied but the average was 19 days. After the onset of estrus bromocryptine administration was usually continued for another 3 to 6 days. Occurrences of estrus, ovulation and pregnancy were monitored by cytological evaluation of vaginal epithelium, rapid ELISA for plasma progesterone and ultrasonography, respectively. Samples for progesterone were taken on Days 7, 9, 12 and 15 and sonograms of ovarian follicles and of fetuses were taken on Days 0, 22 and 35. The bitches involved in the study either regular or irregular cycles. Bromocryptine treatment induced estrus in all of the bitches including 40 of 48 (83%) with ovulation within a regular estrus and 6 of 48 (12.5%) that showed estrus but did not ovulate. Mating or artificial insemination of bitches in their fertile periods twice at two day intervals resulted in an 83% pregnancy rate (40 cases) and 39 (97.5%) of them gave birth to puppies. However, the average litter size was small with 4.8 +/- 1.6 pups.     

Induction of estrus in bitches with normal and persistent anestrus using human menopausal gonadotropin (hMG)

Human menopausal gonadotropin (hMG) was administered intramuscularly to 10 bitches during apparently normal anestrus (n = 7) or persistent anestrus (n = 3). Each dog received a 75-IU dose of hMG (75 IU LH and 75 IU FSH; 1 to 7 units/kg) daily for nine days. Nine bitches responded with obvious signs of proestrus within 3 to 9 days. Of these, 3 bitches exhibited a weak proestrus while 2 exhibited a normal estrus and ovulation but failed to become pregnant The remaining 4 bitches became pregnant at the induced cycle and produced normal litters at 72 to 85 d after the start of treatment, including 1 bitch that had been treated at 24 mo after the last estrus. In 2 cases, treatment resulted in ovulation following 25 or 34 mo of chronic pubertal anestrus, 1 of which became pregnant. The results suggest that hMG can be a useful gonadotropin preparation for inducing estrus in dogs.     

Comparison of two progestogens during out-of-season breeding in a commercial ewe flock

A comparison was made of the relative effectiveness of subcutaneous ear implants containing 2 mg Norgestomet or vagnial pessaries containing 60 mg medroxyprogesterone acetate (MAP) to induce estrus and conception in dry anestrous ewes. Groups of ewes were treated with one of the two progestogens for 14 d, and 500 IU pregnant mare serum gonadotropin (PMSG) was administered intramuscularly at the time of progestogen withdrawal. No significant differences in estrus induction, pregnancy rate or number of lambs born per ewe lambing were observed. Ewes treated with Norgestomet had 96% estrus, 60% pregnancy rate and 1.4 lambs per ewe lambing. Comparably, ewes treated with MAP had 94% estrus, 65% pregnancy rate and 1.7 lambs per ewe lambing. Norgestomet implants compared favorably with MAP pessaries for estrus induction and breeding of commercial, dry anestrous ewes.     

Induction of fertile estrus in bitches using a sustained-release formulation of a GnRH agonist (leuprolide acetate)

A single subcutaneous injection of a sustained-release formulation of a potent GnRH agonist, leuprolide acetate (LA; [D-Leu6, Pro9NEt]-GnRH), was evaluated as a method of inducing fertile estrus in 12 mature anestrous and 6 prepubertal beagle bitches. The bitches were treated with microencapsulated LA (100 micrograms/kg, s.c.) at 120 or 150 d post partum, or at 1 yr of age, followed by a GnRH-analogue (fertirelin; [Pro9NEt]-GnRH, 3 micrograms/kg, i.m.) on the first day of induced estrus. Signs of estrus were seen within 10.3 +/- 0.9 d after LA administration in all bitches. The interestrous interval in 120- and 150-d post-partum bitches was shortened (P < 0.05) to 191 +/- 3 and 222 +/- 3 d, respectively, compared with 264 +/- 11 d in control bitches. All LA treated dogs demonstrated behavioral estrus and mated. Three of 6 (50%) at 120 d post partum, 6 of 6 (100%) at 150 d post partum and 5 of 6 (83%) of prepubertal (1-yr old) bitches then became pregnant and produced a mean litter size of 4.1 +/- 0.8 pups. A normal circulating estrogen and progesterone response pattern was observed in mature anestrous bitches. A prepubertal bitch that failed to become pregnant had a similar estrogen response pattern but an insufficient progesterone profile. The results suggest that microencapsulated LA can be useful in inducing fertile estrus in the domestic dogs.     

Endocrine response of postpartum anestrous beef cows to GnRH or PMSG

Forty-one postpartum anestrous Hereford cows, maintained under range conditions, were used to determine the influence of gonadotropin releasing hormone (GnRH) or pregnant mare serum gonadotropin (PMSG) on ovarian function. Anestrous cows were identified by estrous detection with sterile bulls and concentrations of progesterone in plasma obtained weekly. At 45 +/- 2 days postpartum, cows were allotted to the following treatments: (1) control (saline), (2) 100 mug GnRH, (3) 200 mug GnRH, (4) 200 mug GnRH in carboxymethyl cellulose (CMC), (5) 500 IU PMSG, (6) 1,000 IU PMSG or (7) 2,000 IU PMSG. Cows were bled frequently the first day after treatment and then every other day until 85 days postpartum. The LH responses after 100 and 200 mug of GnRH were not significantly different and mixing 200 mug GnRH with CMC before injection did not significantly alter the LH response. During the first 20 days after treatment, neither GnRH nor 500 IU PMSG altered estradiol concentrations in plasma, but treatment of cows with 1,000 or 2,000 IU PMSG resulted in increased (P<0.01) concentrations of estradiol. The time postpartum required for concentrations of progesterone in plasma to exceed 1 ng/ml was reduced (P<0.05) by all treatments except 100 mug GnRH. These data indicate that GnRH causes LH release in anestrous range cows and that treatment with 1,000 or 2,000 IU PMSG initiates ovarian activity as evidenced by increased concentrations of estradiol in plasma.     

Effects of progesterone pretreatment on fertility of gilts mated at an induced pubertal estrus

The effects of progesterone (100 mg/d, im) on pubertal fertility were examined in 247 gilts over 3 experiments. In the first experiment, 128 gilts were exposed to progesterone for 0, 2, 4 or 8 d before receiving PMSG (750 IU) 1 d later. The number of large (>4mm) follicles or corpora lutea (CL) were determined on the day of PMSG injection, Day 0 (onset of estrus), Day 1 or Day 10 (n=8). In the second experiment, embryonic survival was observed in 68 gilts after induction of estrus with PG600 (400 IU PMSG, 200 IU hCG). Vehicle or progesterone was previously administered for 2 d to these gilts, and they were allowed 1, 2, or 3 d between the last progesterone injection and PG600. In Experiment 3, a field trial was conducted in which 51 gilts received vehicle or progesterone for 2 d, followed by a 3-d interval before injection of PG600 to induce estrus. The gilts were allowed to farrow. Treatment with progesterone 1 d before PMSG increased (P<0.05) the number and size of preovulatory follicles and increased (P<0.05) the number of corpora lutea. However, the percentage of gilts pregnant by Day 10, the number of embryos recovered per gilt and embryonic survival were reduced (P<0.05) with progesterone pretreatment. Utilizing a smaller dose of PMSG (750 vs 400 IU) with PG600 negated the effects of progesterone pretreatment on ovulation rate. When the interval between progesterone treatment and PG600 was lengthened to 3 d embryonic survival to Day 30 improved but was similar to that of the vehicle/PG600 treated gilts. Fertility, as defined as conception rate and litter size, was similar between gilts exposed to vehicle or progesterone. These results indicate that pretreatment with progesterone up to the day before PMSG might improve follicular development and ovulation rate at the pubertal estrus with a dose of 750 IU of PMSG but not with the 400 IU (PG600). Reducing the dose of PMSG to 400 IU and allowing for 3 d between progesterone and gonadotropin treatment reduced the incidence of uterine infections but resulted in a fertility rate similar to that of gilts receiving PG600 alone.     

Ovulation induction in anestrous bitches by pulsatile administration of gonadotropin-releasing hormone

Preliminary studies in anestrous Beagle bitches demonstrated that a single injection of gonadotropin-releasing hormone (150 micrograms) produced a rapid, physiological rise in serum estradiol lasting 1-3 days while progesterone remained below 1 ng/ml, whereas serial injections of FSH rapidly produced greater elevations in estradiol and a rapid rise in progesterone over 2 ng/ml. Consequently, attempts to induce fertile ovulation by means of pulsatile intravenous administration of GnRH (1 pulse/1.5 hours for 6-12 days; 0.04-0.43 micrograms/kg body weight/pulse) were conducted in eight anestrous bitches. Willingness to mate, serum progesterone levels and results of mating were monitored. In six of the eight bitches, vulval and vaginal signs of proestrus occurred by Day 2-4 after initiation of treatment (Day 0); but, two bitches showed negligible responses. In five of the six bitches in which proestrus was induced, behavioral (n = 4) and vaginal (n = 5) correlates of early estrus occurred by Day 5-7 of treatment and breedings occurred over a period of 4-12 days. Following onset of estrus, four of the five bitches had increases in serum progesterone levels between Days 14 and 18 after initiation of treatment (and 4-11 days after cessation of treatment); three of them became pregnant and whelped normal litters (ranging from 9 to 11 pups). The fifth bitch did not have elevated progesterone during the induced estrus, and upon return to estrus one month later was successfully bred and whelped a normal litter of 10 pups.(ABSTRACT TRUNCATED AT 250 WORDS)     

Selective control of the estrous cycle of the dog through suppression of estrus and reduction of the length of anestrus

The objective of this study was to determine the effectiveness of testosterone in suppressing estrus in the bitch, and of cabergoline in shortening the length of the subsequent anestrous period. In Experiment 1, 12 diestrual Beagle bitches were randomly divided into two groups when plasma progesterone (P(4)) concentration was <1 ng/ml (Day 0). Starting on Day 0, bitches in Group 1 (n=6) were treated with testosterone cypionate every 14 days for a total of 239 days, and bitches in Group 2 served as untreated controls. On Day 274, bitches in both groups were treated with cabergoline for 40 days and blood samples were obtained on Days 274, 276 and 279 for determination of plasma prolactin (PRL) concentrations using RIA. All bitches were observed for proestrual bleeding during treatment with cabergoline. In Experiment 2, 12 Greyhound bitches previously treated with testosterone within the last 6 months were randomly divided into two groups. At the initiation of this experiment, P(4) concentration was determined to verify that all bitches had a concentration of <1 ng/ml (Day 0). Starting on Day 0, bitches in Group 1 (n=6) were treated with cabergoline for 36 days, and bitches in Group 2 (n=6) served as untreated controls. Blood samples were obtained on Days 0, 2 and 5 to determine PRL concentrations. All bitches were observed for proestrual bleeding during treatment with cabergoline. In Experiment 1, one bitch (Group 1) exhibited estrus after treatment with testosterone (1mg/kg body weight) for 43 days, and one bitch (Group 1) exhibited estrus after treatment with testosterone (2mg/kg body weight) for 113 days. None of the other four bitches in Group 1 exhibited estrus during the period of testosterone treatment (239 days). All bitches in Group 2 (control) exhibited estrus during the 239 days of the study. In addition, five of the six testosterone-treated bitches showed signs of proestrual bleeding within an average of 12.6 days (range of 5-25 days) after treatment with cabergoline; and, four of the six nontestosterone bitches showed signs of proestrual bleeding within an average of 28 days (range of 6-46 days). Prolactin concentrations in bitches in both Groups 1 and 2 significantly decreased after treatment with cabergoline. In Experiment 2, one of the six bitches showed signs of proestrual bleeding within 15 days after treatment with cabergoline. From the results of this study, it was concluded that exogenous testosterone was moderately effective (66%) in suppressing estrus in Beagle bitches, and cabergoline was effective in shortening the length of the anestrous period of Beagle bitches whose estrous cycle was previously suppressed with exogenous testosterone, but less effective in shortening the length of the anestrous period in Greyhound bitches previously treated with testosterone to suppress estrus.     

Ultrasound and endocrine evaluation of the ovarian response to a single dose of 500 IU of eCG following a 12-day treatment with progestogen-releasing intravaginal sponges in the breeding and nonbreeding seasons in ewes

A standard dose of 500 IU of eCG is commonly given to progestogen pre-treated anestrous ewes for induction of estrus. Twelve seasonally anestrous and 12 cyclic Western White Face ewes were treated for 12 days with intravaginal sponges impregnated with medroxyprogesterone acetate (MAP). In trials in both the breeding and nonbreeding seasons, six randomly selected ewes were given 500 IU of eCG at sponge removal to determine the effects of low dose of eCG on ovarian antral follicular dynamics and ovulation. Ultrasound scanning and blood sampling were done daily. Treatment with eCG did not have marked effects on antral follicular growth. All ewes ovulated, except for five of six control anestrous ewes. Luteal structures and progesterone secretion were confirmed in all but the control anestrous ewes. In the breeding season, peak progesterone concentrations were greater (P<0.05) in eCG-treated compared to control ewes. Daily serum estradiol concentrations were greater in the periovulatory period in eCG-treated compared to control ewes (treatment-by-day interaction; P<0.05), particularly in anestrus. Progestogen-treated ewes ovulated follicles from several follicular waves, in contrast to ovulations of follicles from the final wave of the cycle in untreated, cyclic ewes. Anestrous ewes exhibited more frequent follicular waves and FSH peaks compared to cyclic ewes after a progestogen/eCG treatment. In conclusion, 500 IU of eCG given after 12 days of progestogen treatment had limited effects on the dynamics of ovarian follicular waves. However, eCG treatment increased serum concentrations of estradiol during the periovulatory period, particularly in anestrous ewes; this probably resulted in the synchronous estrus and ovulation in anestrous ewes.     

The effect of cloprostenol and cloprostenol + HCG on corpora lutea and serum progesterone in Brahman cows

Two independent trials were conducted to evaluate 1) the effect of cloprostenol (CLP; ICI 80996) on subsequent corpus luteum size and progesterone content and 2) the effect of CLP and CLP followed by HCG (1500 IU) at estrus on daily serum progesterone levels in Brahman cows.In Trial 1, cows were assigned as untreated controls (n=8) or to receive 500 μg CLP intramuscularly on day 8–12 postestrus (n=9). Corpora lutea were removed surgically and weighed on day 13 after the spontaneous or CLP induced estrus. CL progesterone (P4) was also monitored.In Trial 2, cows were assigned as untreated controls (n=15), to receive 500 μg CLP on day 9, 10 or 11 postestrus (n=10), or to receive CLP as above, plus 1500 IU HCG 12 hr after the CLP-induced estrus (n=10). Daily blood samples were collected from all cows from day 2 postestrus through the second estrus, thus encompassing the period of CL development and regression.The data generated in Trial 1 indicated that CLP depressed CL weight (2.7 vs 4.7 mg; P<.05) and CL P4 content (220.88 vs 367.43 μg; P<.05) as compared to untreated controls. Serum P4 during the time period corresponding with CL development was lower (P<.05) in CLP-treated cows in Trial 2. The most distinct reduction occurred from day 7 through 10. Postestrus treatment with 1500 IU HCG appeared to increase CL steroidogenic capacity, however, a significant (P<.05) difference was not detected between CLP + HCG and CLP or control groups.     

Ovarian response in the estrual cat receiving varying dosages of HCG

Laparoscopy was utilized to determine the ovulatory response of the domestic cat to various dosages of human chorionic gonadotropin (HCG) administered intramuscularly at one or two time periods during estrus. A linear HCG dose-ovulatory response was observed in queens receiving 0--500 IU HCG as a single injection on day 1 or as injections given on days 1 and 2 of estrus. Animals treated with 500 IU HCG on day 1 or days 1 and 2 of estrus produced the maximum percent ovulation rates based on pre- and post-HCG ovarian morphology observation by laparoscopy (100.0, 95.9%, respectively). A single injection of 500 IU HCG produced a significant increase (p less than 0.05) in mean percent ovulation rate in comparison to the 0, 50 and 100 IU HCG single injections. Administration of 500 and 250 IU HCG for 2 days of estrus resulted in a greater percent ovulation rate than the 2-day injection of 50 IU (p less than 0.05). These results indicate that the proportion of mature follicles ovulating in an induced ovulator, such as the cat, is an increasing function of graded dosages of exogenous hormone.     

Efficacy of exogenous gonadotrophic hormones to induce estrus in anestrous gilts

The objective of this study was to examine the response of anestrous gilts to injections of pregnant mare's serum gonadotrophin (PMSG) alone or in combination with human chorionic gonadotrophin (hCG). One hundred and eighty gilts which had failed to exhibit estrus by about 33 wk of age were given one of the following treatments: no injection, 500 IU PMSG, 1000 IU PMSG or 400 IU PMSG + 200 IU hCG. A greater number of gilts injected with 1000 IU PMSG exhibited estrus within nine days of treatment than control gilts (21/37 vs 13/41, X(2) = 5.0, P<0.05). In addition, gilts injected with 1000 IU PMSG exhibited oestrus significantly earlier than gilts receiving the other treatments. In comparisons of the proportion of gilts ovulating within 9 d of treatment and the treatment-to-ovulation interval, there were no significant differences between the three exogenous hormone treatments. There was also no significant effect of treatment on farrowing rate or subsequent litter size. The results of our study indicate that treatment of anestrous gilts with 1000 IU PMSG effectively induces ovulation and fertile estrus. Inadequate expression of estrus often accompanied the ovulation induced by the lower dosages of PMSG used with and without hCG in this experiment.     

The effects of a low dose of cabergoline on induction of estrus and pregnancy rates in anestrous bitches

This is the first report of successful induction of normal estrus and ovulation in breeder bitches with as a low dose as 0.6 microg/kg/day of cabergoline formulation marketed for use in women. Sixty-one pure breed bitches from various breeds were used in the study at their already determined periods of anestrus. Twenty-four dogs formed the control group, while 37 bitches were administered with two different doses of cabergoline (recommended dose group, n=10, 5 microg/kg/day and low dose group, n=27, 0.6 microg/kg/day). Induced estrus rates and mean treatment and proestrus durations of dogs in these two dose groups were compared. At the second phase of the study, the effects of 500 IU human chorionic gonadotropin (hCG) administered on days 1 and 3 of estrus induced by the low dose of cabergoline, on the duration of behavioral estrus, ovulation rates, pregnancy rates and the number of offspring were investigated. For this purpose, the dogs with signs of proestrus (22/27) following the treatment in the low dose group were assigned into two subgroups. Five hundred IU of hCG (Pregnyl, Organon, Turkey) was intramuscularly administered to eight of these dogs [low dose (hCG+) group] on days 1 and 3 of estrus. The remaining 14 dogs were not treated with hCG [low dose (hCG-) group]. An aqueous solution of cabergoline (Dostinex, Pharmacia, Italy) was orally administered until 2 day after the onset of proestrus or for a maximum of 42 days. Blood samples were taken daily from all treatment and 11 control bitches during the first five days of behavioral estrus to measure progesterone concentrations. In the recommended dose and low dose groups, estrus was induced between days 8-45 and 4-48 (mean: 23.63+/-14.33 and 24.41+/-14.31 days), in the ratio of 80.0 and 81.5%, respectively (p>0.05). In both dose groups, post-treatment interestrous intervals were significantly shorter than both those of the control group and their own pre-treatment interestrous intervals (p<0.05). Ovulation rates, pregnancy rates and mean number of offspring delivered by the dogs in the recommended dose, low dose (hCG-), low dose (hCG+) and control groups were found to be similar (p>0.05). However, the mean duration of behavioral estrus of the dogs in the low dose (hCG+) group was found to be significantly longer compared to dogs in all other groups (p<0.05). In both dose groups, no correlation could be found between the anestrus stages and treatment durations (p>0.05). Shortly, it has been concluded from the study that (1) normal and fertile estrus can be induced more economically in bitches during different stages of anestrus using as a low dose of 0.6 microg/kg of cabergoline formulation marketed for use in women, and that (2) hCG injections on days 1 and 3 of the estrus induced by this method has no positive effects on the ovulation rates, pregnancy rates and the number of offspring per pregnancy.     

Ovarian activity in progesterone treated mares following administration of pregnant mare serum gonadotropin

Twelve non-pregnant, non-lactating mares were randomly assigned to four treatment groups using a 2x2 factorial arrangement with three replicates per group. Mares were administered PGF(2alpha) (10 mg, IM) on days -14 and 0, followed by HCG (3000 IU, IM) on day 5. The following treatments were administered: Group A received PMSG on days 2 (4000 IU, IM) and 5 (1000 IU, IV); Group B received PMSG (4000 IU, IM) on day 2; Group C received PMSG (1000 IU, IV) on day; Group D received no PMSG. Mares received progesterone (25 mg, IM) on days 1 through 4. Reproductive tracts were recovered at necropsy on day 16 (10 days post-ovulation). Ovaries were weighed, CL number and weight determined, follicles counted and measured, and volume of follicular fluid quantified. Mean ovarian weight (g) and number of CL per mare, respectively were: Group A, 100.0+/-15.6, 1.7+/-.7; Group B, 128.6+/-40.4, 1.3+/-.7; Group C, 92.4+/-21.0, 2.0+/-.0; Group D, 93.3+/-12.3; .3+/-.3. Mean number of follicles >10 mm and total volume (ml) of follicular fluid per mare, respectively, were: Group A, 9.4+/-2.0, 21.8+/-10.9; Group B, 1.3+/-.3, 32.2+/-28.9; Group C, 4.3+/-1.8, 5.4+/-2.3; Group D, 6.0+/-4.5, 24.0+/-10.3. There was no difference (P>.05) in mean ovarian weight, CL number, CL weight, follicular fluid volume, number of follicles, or size of follicles between treatment groups. These results show no significant effect on ovarian activity in progesterone treated mares following administration of exogenous PMSG.     

Estrus, ovulation and conception following timed insemination in Romney ewes treated with progestagen and gonadotropins.

The estrus — ovulation time relationships was examined in Romney ewes treated with progestogen (intravaginal sponge) and gonadotropins (PMSG + HCG or PMSG alone) prior to (January) and during (April) the breeding season. The conception rate of ewes inseminated at predetermined times after treatment was also investigated.Ewes exhibited estrus sooner after sponge removal in April than in January (34.9 v 38.9 hrs, P < 0.001). The interval from sponge removal to ovulation was also shorter in April than in January (56.3 – 62.1 hrs, P < 0.01). There were no significant differences between treatments or season on the mean interval from estrus to ovulation. Types of gonadotropin treatment had no effect on the estrus — ovulation time relationships. There were no significant effects of season, hormone treatment or time of insemination on lambing rate.     

SUPEROVULATION AND SUPERPREGNANCY IN THE GOLDEN HAMSTER*

Pregnant mare serum gonadotropin (PMSG) treatment given in the morning or afternoon on any day of the four-day estrous cycle and human chorionic gonado tropin (HCG) given two days later successfully induced superovulation in the golden hamster. The minimum interval between PMSG and HCG necessary to obtain consistent superovulation was approximately 44 hr. The lowest ovulation rate was obtained following PMSG treatment on the afternoon of day 4 despite the fact that this time coincides with the maximum endogenous FSH level, necessary for the maturation of the next crop of follicles destined to ovulate. Thirty-eight to one-hundred percent of superovulated females in four different treatment groups became superpregnant after natural mating. Some treated females exhibited two consecutive nights of estrus with ovulation apparently occurring during the second night. Superpregnant females delivered “super” size litters, up to 27 live-born pups. The ultimate litter size appeared to be established after day 3 and prior to day 8 of superpregnancy. A one-day extension of the normal 16-day gestation period was observed in 31% of superpregnancies. Unilateral pregnancies were observed at autopsy in 44% of treated females which received the high dose of PMSG (30 IU). The progeny of superovulated females reproduced normally at maturity. The results indicate that ova from superovulated female hamsters are capable of full normal development.     

Sodium cloprostenol administered at a continuous low dosage induces polydipsia and suppresses luteal function in early dioestrous bitches.

The aim of this study was to determine whether sodium cloprostenol administered at a continuous low dosage induced luteolysis and polydipsia in early dioestrous bitches. Sodium cloprostenol was administered subcutaneously to greyhounds at doses of 4.04-5.19 microg/kg/day (treated group, n=5) or 0 microg/kg/day (control group, n=5) delivered by mini-osmotic pumps for 7 days. The treated bitches and two of the control bitches were in early dioestrus (Days 5-14, and 6 and 10, respectively) when the mini-osmotic pump was inserted (Day 0). Concentrations of plasmatic progesterone were measured in dioestrous bitches each day from Day -2 to 7, and then weekly until Day 90. Daily intake of water was ascertained in all bitches from Day -2 until Day 10, and their weight was measured on Days -2, 6 and 13. Biochemical analyses on plasma for concentrations of urea and glucose, and urinalyses were performed on all bitches before (Day -1), during (Day 4) and after treatment (Day 10). Concentrations of plasmatic progesterone declined dramatically and rapidly in treated bitches after Day 0 to <2.9 ng/ml but were not similarly affected in the dioestrous control bitches. However, in three of five treated bitches, concentrations of plasmatic progesterone increased to >1 ng/ml in the period from Day 10 to 90 indicating that luteolysis was incomplete. All treated bitches were polydipsic (intake of water >100 ml/kg/day) for 2-6 days during the period of treatment, and for 0-2 days immediately after treatment (Days 7 and 8). One control bitch was polydipsic on Days -2, -1 and 0. The treated bitches were also polyuric since they were hyposthenuric (<1.007, n=4) or isothenuric (1.010, n=1) on Day 4, their weight did not increase and no gastrointestinal or respiratory effects were observed. The control bitches were always hypersthenuric when measured during and after treatment (>1.021). Biochemical analyses of plasma and other data obtained from urinalyses did not reveal any differences between groups. This study indicated that sodium cloprostenol administered at a continuous low dosage induced polydipsia and suppressed luteal function in early dioestrous bitches.