Cloprostenol-15-glycal is an analog of natural prostaglandin F2 alpha. It is prepared fully synthetically and is a basic substance of the veterinary medicament of firm name Glystrofan (chem. conc. Spolana, Neratovice, CSR). The effect of this substance was studied after intravenous application in double concentration on the blood cell count in experiment on rats. A significant decrease of erythrocyte count was observed in late sampling intervals especially after higher dose. A temporary elevation of leucocyte count occurred in white blood cell series. There was lymphocyte count elevation, while neutrophil count decreased. In the course of experiment a decrease of thrombocyte count occurred, especially after higher dose. Characteristic of described changes corresponds to that, which was observed by prostaglandins of series E. Changes in perifery blood cell count can be in agreement with the effect of cloprostenol-15-glycal on the production or influence of growth factors and on the proliferation of pluripotent hematogenic cells respectively.

Gonadotropin releasing hormone (GnRH) was given to 109 cows and heifers during the course of 224 superovulations. Follicle stimulating hormone (FSH) was administered twice daily (5 or 6 mg) for 3.5 to 4 days beginning on any of Days 9 to 14 of the estrous cycle; prostaglandin (45 mg PGF(2)alpha or 750 ug cloprostenol) was given in a split dose on the fourth day. Donor cows and heifers were placed into four groups according to previous superovulation treatments, which consisted of one to three treatments or of no previous treatment. Every other cow or heifer within each of the four subgroups was treated with GnRH (200 mug i.m.) at standing estrus. Only donors that exhibited estrus within 32 to 72 h after the first prostaglandin treatment were used in the study. Animals were inseminated artificially 12 and 24 h after standing estrus was first observed. No differences were noted in the number of ovulations, total ova or transferable embryos recovered from the GnRH or control groups; however, two interactions were detected. Cows given GnRH had fewer palpable corpora lutea than control cows (P < 0.05), but this difference was not seen in heifers. The second interaction was that GnRH seemed to depress ovulation rate in donors not previously superovulated, but this effect was not observed with subsequent superovulations. Cows yielded more total ova than heifers (P < 0.01). There was no difference in return to estrus between GnRH and control groups after a second prostaglandin treatment at the time of embryo recovery. Most donors within each group resumed cycling between 5 and 12 d after embryo recovery.

Two trials were performed to evaluate the efficacy of prostaglandins administered via the vulvomucosal route at one-half the recommended dosage in comparison to prostaglandins injected intramuscularly (IM) at the standard dosage. In trial 1, sows on three commercial swine farms were given prostaglandin F2alpha at a dosage of 10 mg IM (n = 110) or 5 mg prostaglandin F2alpha using a vulvomucosal injection (n = 94). The numbers of sows farrowing within 36 h postinjection were 92 (84%) and 83 (88%), respectively. In trial 2, sows on four commercial swine operations were induced to farrow by means of one of three treatments: cloprostenol 175 mug IM (n = 71); cloprostenol 87.5 mug vulvomucosally (n = 57); or prostaglandin F2alpha 5 mg vulvomucosally (n = 96). The numbers of sows farrowing within 36 h postinduction were 69 (97%), 53 (93%), and 91 (94%), respectively.Vulvomucosal injections of prostaglandin F2alpha and cloprostenol at one-half the dosage appeared to be as effective as intramuscular injections of prostaglandin F2alpha and cloprostenol at the recommended level. There were fewer sows demonstrating restless behavior following the injection of lower dosages of prostaglandin F2alpha vulvomucosally, compared to sows given the recommended dosage of prostaglandin F2alpha IM.

Each of 411 Polwarth ewes was given prostaglandin (125 micrograms cloprostenol) by injection on 2 occasions 10 days apart. Ewes were not mated at either prostaglandin induced oestrus, but field mated at the first natural oestrus thereafter. As a result 97.1% mated in a 12 day period (82% in 4 days). From a selected group of 270 ewes, presumed to have been pregnant (by non-return to sevice), 90 were given prostaglandin (125 micrograms cloprostenol) as an abortifacient, at 22-23 days post service, the remaining 180 acting as lambing controls. Pregnancy was finally determined by ultrasonic fetometer at 106-107 days post mating. A 100% accuracy was achieved being confirmed by lambing observations. Most (98.9%) of the control, as expected, proved to be pregnant and subsequently lambed. By contrast only 33 (36.7%) of the prostaglandin treated ewes were pregnant. Thus, although prostaglandin aborted 63.3% of pregnant ewes, its efficacy was much less than might have been expected. The authors then discuss the efficacy of prostaglandin as an abortifacient at various stages of gestation.

In a herd of sows 106 sows having 4.3 litters on aver., were over a period of 10 weeks treated on Thursdays with 0.175 mg of cloprostenol on the 111th to 114th day of gestation; 93--95% of the sows treated on the 112th and 113th day farrowed within 33 hours after treatment, 73% after treatment on the 111th day (Table I); the mean period of gestation after treatment was 113.4 +/- 0.9 days. 8 sows that only farrowed 2--5 days after the treatment, had on 21 previous farrowings proved to have significantly longer mean periods of gestation, 115.6 days, than the 112 sows in the control group, having 3.6 litters on average, that farrowed in the same period and section of the piggery as the sows treated with cloprostenol. In total 32 weekend-farrowings occurred in the observation period including 7 farrowings after a period of gestation of 110--113 days, 6 cases of unsuccessfully induced parturition and 19 farrowings on the 114th to 119th day that could have been programmed to occur on Fridays; the number of weekend-farrowings, which for this herd in connection with the weaning procedure normally accounted for about 40--45% of farrowings, could thus be reduced to 7% of farrowings (Table II). Cloprostenol treatment on the 111th day resulting in farrowing on the 112th day leads to a significantly higher rate of piglet mortality after 3 weeks compared with the results after farrowing for control sows that farrowed on the 112th day (Table III); this category of control sows had on previous farrowings proved to have a significantly shorter mean period of gestation, 112.7 days, than that of the sows in the cloprostenol group farrowing on the 112th day which had been 114.3 days on previous farrowings. Farrowing and weaning results after induced parturition resulting in farrowing on the 113th to 115th day showed no significant differences from the results for control sows farrowing spontaneously on the 112th to 115th day of gestation. The incidence of MMA (Table II) was not influenced by the cloprostenol treatment, nor by the number of litters, the length of the period of gestation, or by the piling of farrowings on Fridays.

Fourteen gilts were aborted (some of them repeatedly) by i.m. administration of 500/ug cloprostenol (PG) between 30 and 100 days of pregnancy so that the total number of PG-induced abortions was 19. Six of these gilts were allowed to terminate their subsequent pregnancy by farrowing. It was found that In a Trial under semi-production conditions the mean birth body mass of piglets from 11 gilts bred after previous PG-induced abortion was 1.48 kg as compared to 1.19 kg in the controls. The difference was significant (P<0.01).

Prostaglandin F2 alpha receptors (PGF2 alpha Rs) were measured in bovine corpus luteum and myometrial cell membranes using a radiometric method. The inhibition of labelled PGF2 alpha binding exerted by d-cloprostenol, dl-cloprostenol, PGF2 alpha and PGE1 (10(-11) M to 10(-4) M) was evaluated in vitro. Results strongly suggest that cloprostenol binding to PGF2 alpha Rs is stereospecific. d-Cloprostenol and PGF2 alpha were equipotent, about 150 times more potent than dl-cloprostenol (P < 0.05) and approximately 280 times more potent than PGE1 (P < 0.05) in inhibiting [3H]PGF2 alpha binding to corpus luteum cell membranes. Such differences were less evident in myometrial cell membranes, where d-cloprostenol and PGF2 alpha were about 10 times more potent than dl-cloprostenol (P < 0.05) and approximately 95 times more potent than PGE1 (P < 0.05).

Trials were conducted to study and describe the micromorphological parameters of endometrium in five cows of the Black-Pied breed after the expiration of the synchronizing effect of cloprostenol in the Oestrophan inj. Spofa preparation. Two animals four to five days after oestrus were used as control and three cows on the sixth day of sexual cycle with rectally palpated corpora lutea were treated intramuscularly with 0.5 mg cloprostenol in 2 ml of Oestrophan. On the eighth day from the administration of the product, samples of uterine horns were obtained by necropsy and were subjected to histological preparation. Paraffin slices, 7 micron thick, were stained with haematoxylin-eosine by the PAS reaction. Changes were observed in the ipsilateral and contralateral uterine horns in relation to active corpus luteum. A state resulting from previous oedematization, with ample thin connective tissue and fading cell infiltration after the administered preparation, was described in the subepithelial layer of endometrium. The occurrence of intraepithelial lymphoid cells was observed in the surface epithelium of endometrium. A significant increase in the thickness of endometrium (P less than 0.001) was observed to persist on the eighth day after the administration of cloprostenol. An increase in the thickness of surface epithelium, ipsilateral with the corresponding corpus luteum, was on the level of significance (P less than 0.05). The subsurface cells of endometrial glands shrunk significantly after the administration of the preparation, both ipsilaterally (P less than 0.001) and contralaterally (P less than 0.001) to the corpus luteum, like in the glands in the depth of the mucous membrane just above myometrium (P less than 0.01). The occurrence of intraepithelial lymphoid cells decreased significantly after the administration of cloprostenol.

The aim of this study was to evaluate the hypothesis that the intravulvar injection of a PGF2alpha analogue at weaning just prior to insemination may minimise the effects of summer infertility in pigs. From July to September 1999, two groups of 30 sows were randomly formed each month. The experimental group comprised sows receiving 37.5 microg of a PGF2alpha analogue, D-cloprostenol, in 0.5 ml injected into the vulvar lips at weaning and at insemination. Group 2 sows received 0.5 ml of saline solution injected into the vulvar lips and served as controls. The percentage of sows in oestrus within 7 days after weaning in treated sows was 27.93% higher than in controls (P<0.001). Fertility for treated sows was also significantly increased by the treatment (P<0.01). However, neither the percentage of inseminated sows that farrowed nor litter size was affected by treatment.

By selective removal and replacement of LH stimulation we sought to examine the relative importance of inhibin and oestradiol in controlling FSH secretion, and the role of LH in the control of ovarian hormone secretion, during the follicular phase of the oestrous cycle. Eight Finn-Merino ewes which had one ovary removed and the other autotransplanted to a site in the neck were given two injections of a gonadotrophin-releasing hormone (GnRH) antagonist (50 micrograms/kg s.c.) in the follicular phase of the cycle 27 h and 51 h after luteal regression had been induced by cloprostenol (100 micrograms i.m.). Four of the ewes received, in addition, i.v. injections of 2.5 micrograms LH at hourly intervals for 23 h from 42 to 65 h after GnRH antagonist treatment. Ovarian jugular venous blood samples were taken at 10-min intervals for 3 h before and 5 h after the injection of antagonist (24-32 h after cloprostenol) and from 49 to 53 h after antagonist (74-78 h after cloprostenol). Additional blood samples were taken at 4-h intervals between the periods of intensive blood sampling. The GnRH antagonist completely inhibited endogenous pulsatile LH secretion within 1 h of injection. This resulted in a marked decrease in the ovarian secretion of oestradiol and androstenedione (P less than 0.001), an effect that was reversible by injection of exogenous pulses of LH (P less than 0.001). The pattern of ovarian inhibin secretion was episodic, but removal or replacement of stimulation by LH had no effect on the pattern or level of inhibin secretion.(ABSTRACT TRUNCATED AT 250 WORDS)

A new HPLC method for the separation and quantification of cloprostenol enantiomers was developed. The optimized separation system consisted of Chiralcel OD-RH column and acetonitrile-sodium dihydrogenphosphate (pH 3.0; 20mM) (33:67, v/v) as the mobile phase. Baseline resolution of (+/-)-cloprostenol (R=2.16) was achieved and the analysis time did not exceed 10 min. Limits of detection and quantification were units of micromol/l at 274 nm. The respective values decreased an order of magnitude at 210 nm. The R.S.D. values obtained for the retention factor, peak area and peak height of each enantiomer were less than 2%. Conditions for semipreparative separation of the enantiomers can be achieved easily just by a small adaptation of the mobile phase composition.

The placentomes were extirpated from 16 cows after parturition induced with 750 micrograms cloprostenol or 20 mg dexamethasone on the 277th day of gravidity, on an average, from 9 cows after spontaneous parturition, and from 7 cows after hysterectomy in the eighth month of gravidity. In the cows with induced calving the foetal placenta was not expelled within 12 hours after calving in 68.7% of the cases whereas in the spontaneous parturitions this proportion was only 22.2% of cases. The placentomes obtained immediately after calf expulsion, and then after four and eight hours, were subjected to histological and histochemical examination. In the terminal crypts of the placentome in cross sections obtained from cows which expelled the placenta in time after natural and induced parturitions, the number of binuclear cells of the fetal syncytium and of cells of the dam epithelium (P less than 0.001) was found to be significantly lower than in the cases of afterbirth retention (1.2 and 3.9; 6.4 and 18.5). The cells of the cow's epithelium of the expelled placentae had a higher activity of acid phosphatase and lipids and the foetal syncytium had a higher activity of non-specific esterase. Increased alkaline phosphatase activity was characteristic of the cow's epithelium in the cases of subsequent retention of afterbirth. These findings should be taken into account in efforts for developing new methods of the induction of parturition if the undesired occurrence of afterbirth retention is to be reduced.

The effects of Cloprostenol administration on porcine luteal lipid and arachidonic acid accumulation were examined in relation to luteal in vitro progesterone and prostaglandin F synthesis in 18 mature gilts at day 12 of the estrous cycle. Basal and net in vitro release of progesterone from luteal tissue was depressed at 8 hr after treatment whereas net in vitro release of prostaglandin F was elevated at 8 hr. Inclusion of copper dithiothreitol or reduced glutathione in the incubation media resulted in minor alterations of in vitro release of progesterone and prostaglandin F and no changes in composition of luteal lipids or fatty acids. Luteal contents of triglyceride had increased by 8 hr after treatment whereas contents of free and esterified cholesterols had increased by 32 hr after Cloprostenol administration. Luteal contents of phospholipid and free fatty acids were not affected by Cloprostenol administration. At 32 hr after treatment, percentages and content of arachidonic acid had increased in luteal cholesterol esters and triglycerides. Although arachidonic acid percentages increased in luteal free fatty acids and phospholipids, calculated arachidonic acid contents did not change following Cloprostenol administration. Induced luteal regression was associated with decreased in vitro progesterone release, increased in vitro prostaglandin F release, and accelerated lipid and arachidonic acid accumulation within the corpus luteum. The effects of altered lipid metabolism on release of prostaglandin F could not be defined. However, availability of arachidonic acid did not appear to be rate-limiting in relation to luteal in vitro prostaglandin F synthesis.

The effects of Cloprostenol administration on porcine luteal lipid metabolism, progesterone production, and prostaglandin F production were examined in 32 pigs at day 12 of the estrous cycle. Pigs were killed between 0 and 18 hours after treatment. Recovered luteal tissue was incubated at 0 C and at 37 C in the absence and presence of dibutyryl cyclic AMP and indomethacin. Net in vitro release of progesterone from luteal tissue was depressed within 1 hour after Cloprostenol treatment whereas net in vitro release of prostaglandin F was accelerated 4 hours after Cloprostenol treatment. Inclusion of dibutyryl cyclic AMP in the incubation media did not alter progesterone production but did enhance prostaglandin F production at 0 and 1 hour after Cloprostenol treatment. Inclusion of indomethacin in the incubation media completely inhibited the Cloprostenol-induced acceleration of in vitro luteal PGF production. Cloprostenol treatment increased luteal triglycerides and decreased luteal free cholesterol and cholesterol esters within 1 hr after treatment. Arachidonic acid percentages in free fatty acids and triglycerides were also increased within 1 hr after treatment. When 37 C and 0 C incubations were compared, in vitro luteal accumulation of free fatty acids was maximum at 1 hr after Cloprostenol treatment. In vitro accumulation of triglycerides in luteal tissue was comparatively uniform at all times examined during the first 18 hr after Cloprostenol treatment. Comparison of 37 C and 0 C incubations further revealed that luteal triglycerides were active in accumulation of arachidonic acid. Inclusion of dibutyryl cyclic AMP and/or indomethacin in the incubation media did not alter luteal lipid contents or fatty acid compositions. Blood plasma progesterone was depressed at 4 hours after Cloprostenol whereas 13,14-dihydro-15-keto-prostaglandin F2a was elevated at 18 hours after treatment. Blood plasma free fatty acids increased 330 percent at 4 hours and free fatty acid compositions also changed at this time. In both luteal tissue and blood plasma, changes in steroid and fatty acid metabolism occurred prior to changes in prostaglandin metabolism, suggesting that Cloprostenol induced functional luteal regression prior to altering prostaglandin metabolism.

The effects of acetic acid administered at an amount of 300 to 600 g (5 to 10 mol) to the rumen of breeding cows, were investigated on ovulation, conception and progesterone levels in the blood and milk of cows with cloprostenol-induced (Oestrophan Spofa) oestrus at a dose of 500 micrograms i.m. In the group of 15 cows exposed to the acetic acid load five cows got in calf after the first insemination (33.3%), and 12 cows (80.0%) after all inseminations in 37.6 days after cloprostenol administration, with the insemination index 1.67 (Tab. I). In the control group (five cows) four cows (80.0%) got in calf after the first insemination, in total all five breeding cows got in calf in 20.6 days after cloprostenol administration, with the insemination index 1.2. In the experimental group of 15 cows a clinical examination of ovaries on day 7 after insemination revealed ovulation disorders in eight cows, that means in 53.3% of the animals (Tab. II). No ovulation disorders were observed in the control group of five cows. Progesterone levels in the blood showed high variability (Tab. III). In the group of cows administered acetic acid they were by more than a half lower (1.49; 0.67; 1.53 per ml) on days 7, 14 and 21 after insemination in comparison with the control group (3.35; 2.5; 3.38 ng per ml). The average progesterone levels in milk (Tab. IV) were 1.27 and 1.53 on day 7, 6.74 and 7.27 on day 14 and 3.52 and 11.85 ng per ml on day 21, respectively, the higher values apply to the control. It was not possible to evaluate reliably from the progesterone levels in the blood and milk if ovulation took place and if the corpus luteum was developing (Tab. V and VI). The clinical control of ovaries on days 7 and 8 after oestrus and insemination was more reliable to determine the ovulation disorders than the progesterone determination in the blood and milk of cows.

The objectives were to (1) evaluate the effectiveness of induction of luteolysis in superovulated (SOV) cows at two distinct time points after embryo flushing; and (2) compare the pattern of LH release after treatment with PGF in cows with single vs. multiple ovulations. In the first experiment, Holstein cows were SOV with 400 IU of FSH following standard procedures. Uterine flushing for embryo recovery was performed 7 days after artificial insemination (Day 0), and cows were randomly allocated into two groups to receive PGF (0.5-mg sodium cloprostenol, intramascular) either immediately after flushing (Day 7 group, N = 19) or 4 days later (Day 11 group, N = 20). Time of luteolysis was determined on the basis of plasma progesterone (P4) concentrations. There was no difference (P>> 0.05) in plasma P4 before treatment between Day 7 and Day 11 groups. A decline in plasma P4 was observed 48 hours after PGF treatment in both the groups (P < 0.0001). In Day 11 cows, P4 continued to decrease thereafter, whereas Day 7 animals had no further reduction in plasma P4. Luteolysis (P4 < 1 ng/mL) occurred in all Day 11 cows. In the Day 7 group, however, luteolysis failure was observed for 11 of 19 cows (57.9%). In cows without luteolysis, plasma P4 increased after the initial PGF-induced decline. The second experiment compared luteolysis in (SOV, N = 6) vs. non-SOV (control, N = 8) cows. Both groups received a single PGF treatment on Day 11 after estrus, and luteolysis was monitored daily by ovarian ultrasonography and plasma P4 measurements. In addition, plasma LH was measured in blood samples taken every 20 minutes for 1 hour during five consecutive days after treatment. A similar percentage of reduction in P4 was observed in both groups 24 hours after treatment; however, SOV cows only reached plasma P4 values similar (P>> 0.05) to controls 96 hours after treatment. There was no difference in initial LH values between SOV and controls (P>> 0.05). The slower decrease in plasma P4 in the SOV group prevented an increase in LH for up to 96 hours after luteolysis induction, whereas LH values increased (P < 0.05) in controls 24 hours after treatment. In conclusion, (1) luteolysis may fail or be incomplete when PGF treatment is given on the day of uterine flushing (Day 7) in SOV cows; (2) induction of luteolysis 4 days later (Day 11) is effective, but the initial high-plasma P4 concentrations result in a slower slope of P4 decline to basal levels, and consequently, delayed increase in LH pulses.

The objective of this study was to increase efficacy of treatment with the dopamine agonist, cabergoline, for inducing abortion in cats by combining it with a synthetic PGF2 alpha analogue, cloprostenol. Side effects of cloprostenol were avoided by using low doses. An oral formulation of cabergoline was chosen to facilitate administration. Cabergoline was given daily (5 micrograms kg-1 day-1) while s.c. injections of cloprostenol were administered every 2 days (5 micrograms kg-1) (2 days)-1). Plasma concentrations of progesterone, side effects and pregnancy outcome were compared with those of five untreated pregnant queens. The treatment was administered from day 30 after first mating in five queens confirmed as pregnant and lasted a mean of 11 +/- 1 days. All treated animals aborted in 9 +/- 1 days without any side effect, except a mild haemorrhagic vulvar discharge. Subsequent fertility of the queens was not compromised. Abortion was mediated by an abrupt and constant decrease in plasma concentrations of progesterone. Progesterone concentrations were lower than 1 ng ml-1 from day 38 onwards in all treated animals and remained at this value thereafter, except for one queen which showed a further increase in plasma progesterone concentration from day 44 without any clinical consequence. In conclusion, a combination of daily oral administration of cabergoline and cloprostenol injections every 2 days appears to be a reliable, safe and practical method for terminating pregnancy in cats at day 30 of pregnancy, when a diagnosis of pregnancy by palpation or ultrasonography can easily be made.

OBJECTIVE

To compare the performance of intravaginal devices containing 1.0 g (DIB) or 1.38 g (CIDR) progesterone and to determine the efficacy of inclusion of equine chorionic gonadotrophin (eCG) into progesterone-based anoestrous cow treatment protocols for New Zealand dairy cows.

METHODS

Anoestrous cows (n = 1,906) from 12 herds were randomly assigned to four treatments: 100 μg gonadorelin (GnRH) at Day -10; 500 μg cloprostenol at Day -3; 100 μg GnRH at Day -1 and fixed time artificial insemination (FTAI) on Day 0 (gonadotrophin-prostaglandin-gonadotrophin [GPG] group, n = 475); GPG with CIDR device (1.38 g progesterone) inserted between Day -10 and Day -3 (CIDR group, n = 477); GPG with DIB device (1.0 g progesterone) inserted between Day -10 and Day -3 (DIB group, n = 477); and DIB with 400 IU eCG at Day -3 (DIB + eCG group, n = 477). Conception rates to FTAI and pregnancy at Day 28 were analysed using generalised estimating equations (GEE). Time to conception and time to return to oestrus were analysed using Kaplan-Meier survival analysis and Cox's proportional hazards regression.

RESULTS

The proportion of cows conceiving to FTAI was 0.34 (95%CI = 0.29-0.37), 0.38 (95%CI = 0.34-0.43), 0.38 (95%CI = 0.33-0.42) and 0.41 (95%CI = 0.37-0.46) for GPG, CIDR, DIB and DIB + eCG groups, respectively. The proportion of cows pregnant by Day 28 was 0.55 (95%CI = 0.51-0.60), 0.57 (95%CI = 0.52-0.61), 0.56 (95%CI = 0.52-0.60) and 0.63 (95%CI = 0.59-0.67) for GPG, CIDR, DIB and DIB + eCG groups, respectively. There was an interaction between treatment and number of days calved (p < 0.05). Cows more than 60 days calved and treated with DIB + eCG had higher FTAI conception and 28-day pregnancy rates than cows treated with GPG (p < 0.001). Median interval to conception did not differ between treatments (p>> 0.05). There were no differences between DIB and CIDR groups for any parameter (p>> 0.05). The range of the relative risk distribution among herds comparing DIB + eCG to DIB groups was greater than that comparing CIDR to DIB groups for conception to FTAI and pregnancy at Day 28.

CONCLUSIONS

The inclusion of eCG into progesterone-based anoestrous cow treatment protocols improves conception to FTAI and 28-day pregnancy rates in cows >60 days calved at treatment compared with a GPG protocol. There was no difference in clinical performance between DIB and CIDR devices.

CONCLUSIONS

The combination of a low payload (1.0 g) progesterone releasing intravaginal device with eCG treatment at device removal within a GPG treatment is a clinically effective treatment for anoestrous in New Zealand dairy cows.

The luteolytic effect of the prostaglandin F2 alpha analogue, cloprostenol, was investigated in red deer by monitoring concentrations of plasma progesterone, the induction of oestrus and ovulation, and fertility. Oestrus was synchronized in 48 adult hinds by intravaginal delivery of exogenous progesterone for 12 days and i.m. injection of 250 iu pregnant mares' serum gonadotrophin at progesterone withdrawal. A single i.m. dose of 500 micrograms cloprostenol was administered at day 4, 6, 8, 10, 12, 14 or 16 of the subsequent oestrous cycle (n = 6 hinds per treatment; day 0 = oestrus). Six other hinds were monitored by intensive collection of blood samples between day 16 and day 19 to define changes in plasma progesterone concentrations during spontaneous luteolysis. Samples of jugular blood, collected every second day throughout the study and every 6 h for 78 h from the time of administration of cloprostenol, were analysed for plasma concentrations of progesterone and LH. Oestrus was detected by continuous observation during the period of intensive collection of blood samples and all hinds were subjected to transrectal ultrasonography to assess pregnancy status. On the basis of changes in plasma progesterone concentrations, cloprostenol induced complete luteolysis in all hinds treated on days 8-16 and in five of six hinds treated on day 6. Oestrus, ovulation and conception occurred in 25 (69%), 28 (78%) and 25 (69%), respectively, of hinds treated on days 6-16 inclusive (n = 36). Luteolysis was incomplete in all hinds treated on day 4, and none of the animals exhibited oestrus or ovulated; luteolysis was incomplete for one hind treated on day 6.(ABSTRACT TRUNCATED AT 250 WORDS)

Our objectives were to investigate potential changes in the size of steroidogenic large luteal cells (LLC) during partial luteolysis induced by a sub-dose of cloprostenol in early diestrus and to determine transcriptional variations in genes involved in corpus luteum (CL) functions. Cows were subjected to an Ovsynch protocol, with the time of the second GnRH treatment defined as Day 0 (D0). On D6, cows were randomly allocated into three treatments: Control (2 mL saline, im; n = 10), 2XPGF (two doses of 500 μg of cloprostenol, im, 2 h apart; n = 8) or 1/6PGF (single dose of 83.3 μg of cloprostenol, im; n = 10). Before treatments and every 8 h during the 48-h experimental period, blood samples were collected and CL volumes measured. Furthermore, two CL biopsies were obtained at 24 and 40 h post-treatment. The 1/6PGF treatment caused partial luteolysis, characterized by sudden decreases in plasma progesterone (P₄) concentrations, luteal volume and LLC size, followed by increases (to pretreatment values) in P₄ and luteal volume at 24 and 40 h post-treatment, respectively. However, at the end of the study, P4, luteal volume and LLC size were all significantly smaller than in Control cows. Temporally associated with these phenotypes, there was a lower mRNA abundance of VEGFA at 24 and 40 h, and ABCA1 at 24 h (P < 0.05). In conclusion, a sudden reduction in CL size during partial luteolysis induced by a sub-dose of PGF_2α analog on day 6 of the estrous cycle was attributed to a reduction in LLC size, although these changes did not account for the entire phenomenon. In addition to its involvement in reducing CL size, decreased VEGFA mRNA abundance impaired CL development, resulting in a smaller luteal gland and lower plasma P₄ concentrations compared to Control cows.

Keywords: Gene expression; Large luteal cells atrophy; Luteogenesis; Partial luteolysis.

High-yielding dairy cows (199) were allotted to a control group or one of two groups for synchronization of estrus. Synchronization of estrus was accomplished by either insertion of a progesterone-releasing intravaginal device (progesterone coil) for 7 days with .5 mg of the prostaglandin analogue cloprostenol (Estrumate) administered 1 day before removal of the progesterone coil, or by administration of .5 mg of Estrumate followed 13 days later by a progesterone coil inserted for 9 days. Following each estrous synchronization regimen, cows were inseminated during a fixed 6-day period (insemination week). Into one-half of the cows of each treatment group, a second progesterone coil was inserted 12 days following the fixed-time insemination for 9 days. Cows that calved within 21 days were included in a cluster and were treated and inseminated simultaneously at regular 3-wk intervals. Thus, insemination of synchronized cows was during only 6 out of each 21 days. The estrous synchronization regimens were applied so that the first fixed-time insemination for any cow occurred between 59 and 79 days after calving. Control cows were inseminated following estrus, commencing 59 days after calving. Conception rates for cows of groups 1, 2, and 3 were 50, 56, and 51%. Pregnancy rates at 25 days following the fixed-time insemination were 53, 78, and 69%, and at 100 days after calving, 57, 75, and 65%. A system of reproductive management is proposed in which observations for estrous behavior and inseminations are only during 6 days out of each 3 wk.

The study tested the hypothesis that reduced intravaginal implant progesterone (P(4)) concentration to synchronise oestrus would increase pregnancy rates to fixed-time artificial insemination (FTAI) in Bos indicus heifers. Brahman heifers (n = 294; 2 year) were body condition scored (BCS), weighed and scanned for presence of a corpus luteum (CL). Only cyclic heifers were selected and allocated randomly within BCS and 25 kg bodyweight category to one of three P(4) treatment groups. On day 10, heifers received a P(4) implant (CueMate-1-pod, 0.78 g P(4); CueMate-2-pod, 1.56 g P(4); or CIDR-B, 1.9 g P(4)), 2 mg oestradiol benzoate (ODB) intramuscularly (i.m.) and 250 ug cloprostenol i.m.. At day 2, the implant was removed, 250 ug cloprostenol was injected i.m. and tail paint applied. The heifers received 1 mg ODB 24 h later and were FTAI 48-54 h after implant removal (day 0). Ten randomly selected heifers per group were blood sampled and scanned at days 10, 2, 0 and 6 to define the P(4) profiles pre- and post-FTAI. Heifers were heat-detected 18-20 days post-FTAI and oestrous heifers AI'd by the AM/PM rule. Bulls joined the heifers on day 27 post-FTAI. Transrectal ultrasonography estimated conception date on day 72. Statistical analysis examined the effects of treatment, technician, semen, ovarian status, BCS and liveweight, on pregnancy rate (PR) to FTAI. There was no significant difference (p = 0.362) in PR between treatment groups (CueMate 1-pod, 36.4%; CueMate 2-pod, 39.6%: CIDR-B, 28.3%), but PR was higher in those heifers with increased BCS between FTAI and pregnancy diagnosis (p = 0.005). Thirty-three per cent of monitor heifers had plasma P(4) concentrations of <1 ng/ml on day 6 after FTAI; only 20% of these conceived vs 60% of heifers with P(4) ≥ 1 ng/ml. In summary, no significant difference in PR was identified between treatments but good BCS and a rising plane of nutrition were critical to PR of these pure grade Brahman heifers in northern Australia.

Oestrus was synchronized in 46 Afrikaner and Mashona beef cows by two injections of cloprostenol 11 days apart. All cows had a history of sub-optimum reproductive performance. Cows were inseminated up to three times after the second cloprostenol injection on the basis of observed oestrus and changes in the conductivity of cervical mucus. Half the cows received daily injections of 1000 i.u. HcG from days four to 19 after their last insemination; the other half received daily injections of 2 ml saline over the same period. Concentrations of progesterone in plasma was determined from samples taken on days 6, 8 and 22 after the last insemination. Treatment did not significantly affect conception rate and overall conception rate was 39 per cent. On day 8 after insemination none of the 8 cows that had progesterone levels of less than 1 ng/ml were pregnant when examined at day 70. Mean progesterone concentrations were not significantly different between treated and control cows on days 6 and 8, but were significantly higher (P<0,05) in treated cows by day 22. The practical significance of using HcG to stimulate luteal function in the early post-inseminaion period is discussed.