The effects of the luteolytic and luteotrophic agents cloprostenol, human chorionic gonadotrophin (hCG) and melatonin on the corpus luteum have been investigated in marmoset monkeys treated with an LHRH antagonist to reduce endogenous LH secretion. This has allowed the effects of these agents to be investigated in the absence of the principal endogenous luteotrophin. Administration of the LHRH antagonist ([N-acetyl-D beta Nal1-D-pCl-Phe2-D-Phe3-D-Arg6-Phe7-Arg8-D-Ala10]NH2-LHRH) or cloprostenol between days 7 and 11 after ovulation (preimplantation) resulted in luteolysis. A significant (P less than 0.05) decrease in progesterone concentrations had occurred by 4 h after administration of the LHRH antagonist and was indeed preceded by a fall in LH concentrations. Coadministration of hCG with the LHRH antagonist prevented the fall in progesterone. In contrast, administration of cloprostenol resulted in an immediate fall in progesterone concentrations, to less than half the initial level within 1 h, and co-administration with hCG did not prevent the fall. Administration of hCG stimulated progesterone production when given 8 h after the LHRH antagonist but not after 24 h. Cloprostenol prevented the stimulation by hCG. Co-administration of melatonin with the LHRH antagonist did not prevent the decrease in progesterone concentrations. Melatonin was also not effective in preventing the fall in progesterone induced by cloprostenol. However, co-administration of melatonin and cloprostenol between days 17 and 21 after ovulation (post-implantation) significantly (P less than 0.05) delayed the fall in progesterone seen with cloprostenol alone. These results suggest that while the LHRH antagonist and cloprostenol have different sites of action their effect is similar at the corpus luteum, that is in depriving the corpus luteum of luteotrophic support. The results also suggest that melatonin may be able to influence the luteolytic action of cloprostenol but that its effect varies with the stage of the cycle. The physiological role for such an action, if any, remains unknown.

Twenty-six dairy cattle were treated with dexamethasone during medium to late pregnancy to induce premature calving. Thirteen produced calves within an average of 5-6 days of treatment. The remainder were given a subsequent injection of cloprostenol 10 days after the steroid treatment and, with one exception, all calved within the following two days. A high incidence of retained placenta was experienced, in common with other methods of inducing parturition, but this was not generally found to be associated with detrimental effects on health or fertility.

The objective of this study was to evaluate the effects of equine chorionic gonadotropin (eCG) treatment on the number of induced accessory corpora lutea (CL), plasma progesterone concentrations and pregnancy rate in cross-bred heifers after transfer of frozen-thawed (1.5M ethylene glycol) embryos. All recipients received 500 microg PGF2alpha (dl-cloprostenol, i.m.) at random stages of the estrous cycle (Day 0) and were observed for estrus for 7 days. On Day 14, heifers detected in estrus between 2 and 7 days after PGF2alpha treatment were randomly allocated to four groups ( n=83 per group) and given 0 (control), 200, 400, or 600 IU of eCG. Two days later (Day 16), these recipients were given PGF2alpha and observed for estrus. Six to eight days after detection of estrus, plasma samples were collected to determine progesterone concentration and ultrasonography was performed to observe ovarian structures. Heifers with multiple CL or a single CL >15 mm in diameter received an embryo by direct transfer. Embryos of excellent and good quality were thawed and transferred to the recipients by the same veterinarian. Pregnancy was diagnosed by ultrasonography and confirmed by transrectal palpation 21 and 83 days after embryo transfer (ET), respectively. Plasma progesterone concentrations on the day of transfer (Day 7 of the estrous cycle) were 3.9+/-0.7, 4.2+/-0.4,6.0+/-0.4 and 7.8+/-0.6 ng/ml for groups Control, 200, 400, and 600, respectively (Control versus treated groups P=0.009; 200 versus 400 and 600 groups P=0.0001; and 400 versus 600 P=0.012 ). Conception rates 83 days after ET were 41.9, 50.0, 25.0, and 20.9% for groups Control, 200, 400, and 600, respectively (200 versus 400 and 600 groups P=0.0036 ). In conclusion, an increase in progesterone concentration, induced by eCG treatment, did not improve pregnancy rates in ET recipients. Conversely, there was a decline in conception rates in the animals with the highest plasma progesterone concentrations.

One hundred-fifty-two dairy cows affected with pyometra were treated either with cloprostenol (CLP) or with estradiol cypionate (ECP). The cows which failed to respond within 7-10 days were re-treated with the same drug used in the first treatment. Half of the cows which responded to these treatments received intrauterine infusions with 50 cc nitrofurazone solution. After two treatments, 72 (94.9%) of 79 cows in the CLP group had evacuated the purulent exudate from their uteri whereas only 57 (78.1%) of 73 cows in the ECP group had responded (P<0.005). Treatment-to-breeding and treatment-to-conception intervals were not different between the ECP and CLP groups. The number of services/conception was not different up to the 4th service (3.16 vs 3.57, respectively, P>0.1). Eight (9.3%) of 86 CLP treated and 3 (5.1%) of 59 ECP treated cows had recurrence of pyometra (P>0.1). Incidence of follicular cysts within 30 days after treatment was 16.4% (13 79 ) and 7.0% (4 57 ) among CLP and ECP groups, respectively (P>0.1). Two of 106 CLP (1.9%) and 5 of 107 ECP treatments (4.7%) were associated with subsequent perimetritis and adhesions. Intrauterine infusion of nitrofurazone increased the number of services/ conception (3.57 vs 2.21, P<0.01). Cloprostenol was superior to ECP as an initial treatment of bovine pyometra. Intrauterine infusion of nitrofurazone following evacuation of the uterus appeared not to be effective in prevention of relapses and had a negative effect on conception rates.

1. Arterial and mammary venous concentrations of prostaglandins F alpha (PGF alpha), E (PGE) and the PGF alpha metabolite, 13,14-dihydro-15-oxoPGF alpha (DHK-PGF alpha) were studied during late pregnancy and the onset of lactation in conscious goats. Mammary secretion concentrations of PGF alpha and DHK-PGF alpha were determined, and mammary blood flow, arterial plasma progesterone concentrations and milk composition were also studied. 2. A significant output of PGF alpha from the mammary gland into mammary venous blood was observed during late pregnancy; this output ceased near term. 3. Mammary output of DHK-PGF alpha into venous blood began about 6 days prepartum, suggesting an increasing capacity of the gland to metabolize PGF alpha. 4. The concentration of PGF alpha in mammary secretion increased from about 4 days pre-partum, that of DKH-PGF alpha from about 12 days pre-partum. 5. It is concluded that although total mammary output of PGF alpha decreases during late pregnancy and early lactation, the rate of mammary synthesis of PGF alpha increases and the PGF alpha is increasingly secreted into milk and metabolized to DHK-PGF alpha within the mammary gland. 6. Unilateral treatment of one mammary gland in goats with the PGF 2 alpha analogue, Cloprostenol, at two dose levels from 2-3 days pre-partum to 1-2 days post-partum prevented the changes in milk [Na] that occur at term in untreated glands. At the higher dose, the normal rise in milk [citrate] was abolished and milk yield was reduced; these effects persisted after cessation of treatment. 7. It is suggested that PGF alpha may play a local inhibitory role in mammary gland function during late pregnancy. It is further suggested that PGF alpha could be the factor, or one of the factors, proposed by Linzell & Peaker (1974) to be responsible for local control of mammary epithelial permeability and possibly also for secretory rate.

Luteal gonadotropin receptors decrease in cows, sheep and rats within 24 h following an injection of a luteolytic dose of prostaglandin (PG) F2 alpha. But it is not known whether this decrease is the specific event, or a reflection of general decline in luteal cell structure, function and metabolism. In order to investigate this possibility, 15 of 21 heifers were given on day 9 of the estrous cycle, a single 500 micrograms injection of Cloprostenol (CO), a synthetic PGF2 alpha analog. These heifers were ovariectomized in groups of 5 at 12, 24 and 36 h after CO. For controls, a group of 6 heifers were ovariectomized just prior to injection of the others. Serum progesterone levels decreased whereas LH levels increased (P less than 0.05) by 12 h with no additional changes observed at 24 or 36 h. The luteal plasma membranes [125I]hCG specific binding, as well as 5'-nucleotidase (5'-NE) activity, decreased by 12 h and continued to decline (P less than 0.05) until 24 h (binding) or 36 h (5'-NE). Scatchard analysis showed that the decrease in [125I]hCG binding was due to a decrease in receptor number rather than a decrease in receptor affinity. The activities of cytochrome c oxidase in mitochondria, NADH cytochrome c reductase in rough endoplasmic reticulum and galactosyl transferase in Golgi decreased while NAD pyrophosphorylase in nuclei virtually disappeared following the injection of CO. The beta-N-acetyl-D-glucosaminidase (a lysosomal hydrolase) activity in the homogenate increased by 12 h and continued to increase up to 36 h.(ABSTRACT TRUNCATED AT 250 WORDS)

The administration of cloprostenol by intravulvosubmucous (i.v.s.m.) injection at 1 2 and 1 4 of the dose usually given by intramuscular (i.m.) injection, was tested in dairy cows for luteolysis and estrus synchronization. The i.m. injection was used in ten adult cows at the usual dose of 500 mug/animal. Eleven adult cows and 11 heifers were treated i.v.s.m. with a dose equivalent to 250 mug/animal and 125 mug/animal, respectively. Two injections of cloprostenol were administered 11 days apart to the cows not detected in oestrus after a single injection. Forty-three out of the total 46 animals were detected to be in dioestrus at the time of at least one of the injections, as reflected by the plasma progesterone concentrations at the time of treatments. Three out of the 43 animals injected during dioestrus were refractory to the luteolytic effect of cloprostenol; this appeared to be independent of the dosage and the route of administration (refractory cows were: one adult cow treated i.m. and two treated i.v.s.m. with 125 mug of cloprostenol). The mean time interval from injection to the onset of heat was 82.8 hours with a confidence limit for 95% of probability between 67.9 hours and 92.7 hours. The difference between treatments is not significant. The results suggest that in heifers and adult cows cloprostenol can be given i.v.s.m. route at a reduced dose of 1 4 of the usual 500 mug i.m. dosage without affecting the luteolytic effect of the drug or fertility.

This study was conducted to identify factors affecting PGF(2alpha) efficacy to synchronize estrus in water buffalo cows. After detection of a corpus luteum (CL) by rectal palpation, cows were treated (im) with dinoprost (12.5, 25 or 50mg) or D(+) cloprostenol (75, 150 or 300 microg) in a total of 66 treatments. Blood samples were collected 0, 24 and 48 h after treatment and ultrasound examinations and observations for estrus were performed daily to the day of ovulation or to 6 days after treatment. No PGF(2alpha) dose-response pattern was observed and overall rates of luteal regression (progesterone <1.0 ng/ml at 48 h), estrus, no detected behavioral estrus with ovulation occurring, and ovulation were 71.2, 36.4, 19.7 and 54.5%, respectively. To analyze plasma progesterone concentrations and ovarian dynamics, cows were divided in three groups according to their response to treatment. Cows that failed to have ovulations from a follicle after treatment (Group A, n = 30) had (P < 0.05) a lower plasma progesterone concentration (2.98 ng/ml) and smaller CL area (CLA; 187.3 mm(2)) before treatment as compared with cows that had an ovulation from a follicle (4.43 ng/ml and 223.7 mm(2), respectively; Groups B and C, n = 36). In cows that failed to ovulate, plasma progesterone concentration decreased in the first 24 h, but did not decline further and was >1.0 ng/ml 48 h after treatment. Moreover, no significant change in CLA after treatment was detected, indicating that treatment induced only partial luteolysis. In cows that ovulated, plasma progesterone concentration and CLA decreased continuously from treatment to ovulation (consistent with complete luteolysis). Threshold values of 2.8 ng/ml for plasma progesterone concentration and 189 mm(2) for CLA were identified as the best predictors of ovulation before treatment (83.3 and 80.6% sensitivity and 58.6 and 65.5% specificity, respectively, with positive and negative predictive values around 71%). When the origin of the ovulatory follicle was investigated, the interval from treatment to ovulation was shorter (91.9 versus 113.3 h; P < 0.05), and the ovulatory follicle had a slower growth rate (1.02 versus 1.55 mm per day; P < 0.005), a lesser increase in diameter from treatment to ovulation (4.7 versus 8.0 mm; P < 0.001), and a greater maximum diameter (13.2 versus 12.1 mm; P < 0.05) in cows that ovulated from the largest follicle present in the ovary before treatment (Group B, n = 27) compared with cows that ovulated from the second largest follicle present in the ovary before treatment (Group C, n = 9). In summary, the efficacy of PGF(2alpha) for causing luteolysis and synchronizing estrus and ovulation in buffalo cows was dependent upon plasma progesterone concentration, CL size and ovarian follicular status before treatment.

The pregnancy rate in 321 Friesian dairy replacement heifers was not different following two inseminations on a fixed time basis when oestrus was synchronised with either a 12-day progesterone treatment using silastic coils or a double injection regimen of a synthetic analogue of prostaglandin f2alpha (chloprostenol). There was a significantly higher (P less than 0-01) pregnancy rate following insemination when 143 Hereford-cross beef suckler cows were treated with the 12-day progesterone treatment (55 per cent pregnant) in comparison to the pregnancy rate following insemination of 131 cows receiving the double injection of cloprostenol 12 days apart (32 per cent pregnant). The ovarian activity at the start of treatment affected pregnancy rate following the cloprostenol regimen but not following the progesterone regimen. In suckler cows in these trials where ovarian activity was classified at the start of treatment, 30 per cent had inactive ovaries, indicating the magnitude of the problems of synchronising oestrus in beef suckler cows.

Blood samples were collected from 84 buffalo cows 21 days after fixed time artificial insemination following oestrus synchronisation and cloprostenol. Progesterone concentration in plasma was determined by radioimmunoassay. The animals were examined for pregnancy by rectal palpation 60 to 90 days after insemination. Forty-two animals were predicted pregnant on the basis of progesterone concentration (more than 1.0 ng per ml), and 28 (66.7 per cent) of them were subsequently confirmed pregnant by rectal palpation. Thirty-five animals were predicted non-pregnant (progesterone less than 0.7 ng per ml), in 34 (97.1 per cent) this proved to be so. Of the total number, seven (8.3 per cent) were classified as doubtful because their progesterone concentrations were within the range 0.7 to 1.0 ng per ml: two of them were confirmed pregnant and the other five non-pregnant. Out of 31 animals diagnosed pregnant by rectal palpation, 28 (90.3 per cent) had been correctly detected by assay at 21 days. Thirty-four (64.2 per cent) of the 53 animals found non-pregnant had been correctly detected by assay. It was concluded that the determination of plasma progesterone concentration 21 days after insemination was an accurate method of predicting non-pregnancy in buffaloes.

The aim of the current study was to determine possible differences in ovarian and pituitary features explaining lower fertility rates in sheep with oestrus induced with intravaginal progestagens or prostaglandin analogues (group FGA and PGF, n=8 in both) when compared to a control group (group C, n=8). The growth profiles and the mean individual sizes of preovulatory follicles were similar between groups; however, the number of preovulatory follicles per ewe and, consequently, the number of ovulations were higher in groups FGA and PGF (2.3±0.3 and 2.0±0.1, respectively) than in group C (1.4±0.1, P<0.05). However, plasma oestradiol concentrations were similar between groups suggesting a defective function in some preovulatory follicles of groups FGA and PGF. In group FGA, the basal LH levels during the follicular phase were lower (0.21±0.0 ng/mL, P<0.005) than in groups C (0.41±0.1 ng/mL) and PGF (0.55±0.1 ng/mL); the onset of preovulatory discharge being later (21.0±2.3h vs. 12.8±1.5 in C and 14.5±1.5 in PGF; P<0.05 for both). Finally, luteal activity was also found to be affected in group FGA; the rate of progesterone secretion per total luteal tissue was lower (range: 0.46-0.65 ng/mL/cm(2)) than in ewes treated with cloprostenol (2.1-3.3 ng/mL/cm(2)) and control sheep (2.0-3.4 ng/mL/cm(2)).

The recent cloning of several cDNAs encoding prostaglandin (PG) receptors has paved the way for a more detailed investigation of the postulated regulatory role of prostaglandins in corpus luteum function. We have utilized the reverse transcription-polymerase chain reaction (RT-PCR) to isolate a mRNA encoding the ovarian PGF(2alpha) (FP) receptor, using oligonucleotides based on the recently cloned mouse cDNA as primers. The 5'-untranslated region of the rat ovarian mRNA was isolated following 5'-RACE (rapid amplification of cDNA ends). The isolated 1526 base-pair sequence, which spans the entire open reading frame, was found 100% identical in the protein coding region to a similar sequence isolated from a rat astrocyte cDNA library, but different in the first 32 nucleotides of the 5'-untranslated region, possibly due to tissue-specific splicing heterogeneity. Using ribonuclease protection assay, a quantitative analysis of FP receptor mRNA levels was performed in corpora lutea excised from adult pseudopregnant rats (Day 8) at different timepoints (0.5-48 h) following the in vivo s.c. regimen of a luteolytic dose of the FP receptor agonist cloprostenol (5 microg). Already 3 h after cloprostenol injection, FP receptor mRNA levels exhibited a pronounced increase to values 4.0-fold higher (P < 0.01) than before injection. At 7 h through 24 h, the amount of luteal FP receptor mRNA decreased, approaching preinjection levels, whereafter they were again 3.0-fold higher (P < 0.01) at 48 h than before injection. We conclude that following homologous stimulation of the FP receptor, abundance of this mRNA is tissue-specifically regulated in a dynamic pattern, suggestive of an important role for FP receptor-mediated action on gene expression during the demise of corpus luteum function.

Prostaglandins are widely used in herd management due to their luteolytic properties. They have also a direct effect on the myometrium. We hypothesized, that dissimilar prostaglandin preparations would differ as to their contractile effect. Intrauterine pressure was recorded during the diestrus of lactating dairy cows using a transcervically placed intraluminal pressure microtransducer. After recording physiologic uterine motility for 30 min, prostaglandins (dinoprost, DL-cloprostenol, D-cloprostenol) or a placebo was administered intramuscularly, followed by a 2-h recording period. Significant differences were found for the area under the curve (P < or = 0.05) and mean amplitude (P < or = 0.05), whereas the number of spikes per 15 min and the baseline pressure during the last 3 min of every recording period did not differ significantly among treatments. Peak values for area under the curve and mean amplitude were found between 15 and 30 min after administration of DL-cloprostenol, while dinoprost yielded the steadiest plateau from this period until the end of the recording session. These results contrast with those of earlier studies comparing prostaglandins after intravenous administration.

A field trial was conducted to assess the efficacy of a combined prostaglandin F(2)alpha analogue (<em>cloprostenol</em>) and dexamethasone treatment as an abortifacient in feedlot heifers. Heifers were grouped according to stage of gestation as follows: Group I, one to four months, n = 37: group II, four to six months, n = 40: group III, six to eight months, n = 40: group IV, one to eight months, n = 29. Heifers in groups I, II and III received a simultaneous intramuscular injection of 500 mug <em>cloprostenol</em> and 25 mg dexamethasone at the time of rectal palpation for pregnancy diagnosis. Heifers in group IV were subjected to rectal palpation for pregnancy diagnosis but received no treatments. Heifers were observed daily for two weeks for abortion and rectal palpations were done 50 days after treatment to determine reproductive status. HEIFERS ABORTING AFTER TREATMENT WERE AS FOLLOWS: Group I, 37/37; group II, 37/40, group III, 37/40; group IV, 0/29. In each of groups II and III there was one pregnancy and two cases of fetal mummification. The numbers of abortions in groups I, II and III were significantly different from that in group IV (P</=0.01). Weight gains were satisfactory and there was no illness associated with treatment. Results indicate that a combination of prostaglandin F(2)alpha analogue and dexamethasone will induce abortion at all stages of pregnancy in feedlot heifers.

Measurements of venoarterial concentration differences across the ovary in anesthetized sheep have demonstrated that the ovary secretes ovine neurophysin I/II (oNP I/II) and that this process is stimulated by the prostaglandin F2 alpha analogue, cloprostenol. A parallel increase in the secretion of oxytocin (OT) was observed in response to cloprostenol, and the mean molar ratio of oNP I/II to OT secreted was 1.2. There was no detectable ovarian secretion of oNP III. Secretion of oNP I/II and OT was absent after hysterectomy. The data support other evidence indicating that the corpus luteum synthesizes OT, and confirm that the neurophysin associated with OT in the sheep is oNP I/II.

The effects of luteolytic doses of PGF2 alpha (25 mg Dinoprost) and its synthetic analogues Cloprostenol (500 micrograms), Luprostiol (15 mg) and Tiaprost (525 micrograms) on bovine myometrial activity were investigated using a miniature pressure transducer placed in one uterine horn. The compounds were administered intravenously to 4 lactating cyclic cows at diestrus, proestrus, estrus and metestrus. Intrauterine pressure changes were assessed by computerized planimetry of the pressure tracings 30 minutes before and 60 minutes after treatment. Baseline intrauterine pressure was set at zero and treatment effects were expressed as percent change from an equivalent control period (= 100%). Following administration of Dinoprost there was a significant increase of uterine contractility in diestrus (515%), proestrus (198%) and metestrus (256%), but not in estrus. In comparison to PGF2 alpha the analogues Luprostiol and Tiaprost were less effective (Luprostiol: 195% and 154% in diestrus and proestrus resp., Tiaprost: 215% during diestrus), while Cloprostenol did not cause a significant change of intrauterine pressure in any stage of the estrous cycle. The results indicate that the myotonic effects which F2 alpha-prostaglandins exert on the uterus of cycling cows is affected both by the type of prostaglandin and the stage of the estrous cycle.

Prostaglandins are commonly used in herd management for their luteolytic properties; however, prostaglandins also have a direct contractile effect on the myometrium. We hypothesized that different dosages (0.15 and 0.3 mg) of d-cloprostenol, a synthetical prostaglandin F2 alpha preparation, would differ as to their contractile effects on the uterus. Intrauterine pressure was recorded during dioestrus of lactating dairy cows, using a transcervically placed intraluminal pressure microtransducer. After recording of physiological uterine motility for 30 min, a placebo or d-cloprostenol at one of the two different dosages was administered intramuscularly, followed by a 2-h recording period. Significant differences were found for the area under the curve (P < or = 0.05) and mean amplitude (P < or = 0.05), whereas the number of spikes per 15 min and the baseline pressure during the last 3 min of every 15-min period did not differ significantly among treatments. Peak values for area under the curve and mean amplitude were found between 15 and 30 min after administration of the lower dosage of d-cloprostenol, and between 75 and 90 min after administration of the higher dosage. Using the higher dosage of d-cloprostenol, a steady plateau from 15 to 30 min after administration until the end of the recording session was obtained. Thus, double the luteolytic dose of the d-cloprostenol preparation gives a significantly better reaction in terms of uterine contractility than the single dose.

Natural prostaglandins (PG) F2alpha and E1 as well as (+)-cloprostenol were regioselectively 11-acylated using Novozym 435 as a catalyst and vinyl acetate as an acyl donor. Unlike the above compounds the 15-OH group of PGE2 was also acylated with a significant velocity under the same conditions. The enantiospecificity of the lipase-catalysed 11-acetylation of cloprostenol was established by separate treatment of(+)- and (-)-cloprostenols.

Oestrus was induced 4-7 days after treatment with Cloprostenol (ICI 80,996) in gilts between 12 and 40 days pregnant. Fertility at this synchronized oestrus was good (85%).

A screening among bacterial strains isolated from water-brine interface of the deep hypersaline anoxic basins (DHABs) of the Eastern Mediterranean was carried out for the biocatalytical resolution of racemic propyl ester of anti-2-oxotricyclo[2.2.1.0]heptan-7-carboxylic acid (R,S)-1, a key intermediate for the synthesis of D-cloprostenol. Bacillus horneckiae 15A gave highly stereoselective reduction of (R,S)-1, whereas Halomonas aquamarina 9B enantioselectively hydrolysed (R,S)-1; in both cases, enantiomerically pure unreacted (R)-1 could be easily recovered and purified at molar conversion below 57-58%, showing the potential of DHAB extremophile microbiome and marine-derived enzymes in stereoselective biocatalysis.

Administering gonadotropin-releasing hormone (GnRH) improved conception rates in our previous studies. Our objective was to determine if the effect of GnRH was mediated through serum luteinizing hormone (LH) and/or by altered secretion of serum progesterone (P) and estradiol-17 beta (E) during the periestrual and post-insemination periods. Cattle were given either GnRH (n = 54) or saline (n = 55) at 72 h and inseminated artificially (AI) 80 h after the second of two injections of either prostaglandin F2 alpha or its analog, cloprostenol. Progesterone and E were measured in blood serum collected during 3 wk after AI (estrus) from 60 females. Blood was collected for LH determinations via indwelling jugular cannulae from 14 cows and 11 heifers. Collections were taken every 4 h from 32 to 108 h after the second PGF injection (PGF-2) (periestrual period) and at more frequent intervals during 240 min after administration of GnRH (n = 18) or saline (n = 7). Ten females had a spontaneous preovulatory LH surge before GnRH treatment (GnRH-spontaneous), whereas GnRH induced the preovulatory LH surge in six females. A spontaneous LH surge appeared to be initiated in two heifers at or near the time of GnRH treatment (spontaneous and/or induced). The remaining seven cows had spontaneous LH surges with no subsequent change in LH after saline treatment. Serum P during the 21 days after estrus was lower (p less than 0.05) in both pregnant and nonpregnant (open) cattle treated previously with GnRH compared with saline. Serum P during the first week after estrus was greater (p less than 0.01) and increased (p less than 0.05) more rapidly in saline controls and in GnRH-spontaneous cattle than in those exhibiting GnRH-induced or GnRH-spontaneous and/or-induced surges of LH. Conception rate of cattle receiving GnRH was higher (p = 0.06) than that of saline-treated controls. These data suggest that GnRH treatment at insemination initiated the preovulatory LH surge in some cattle, but serum P in both pregnant and open cows was compromised during the luteal phase after GnRH treatment. Improved fertility may be associated with delayed or slowly rising concentrations of serum progesterone after ovulation.

The effect of malathion on jugular plasma concentrations of follicle-stimulating hormone (FSH), estradiol (E2), progesterone (P4) and acetylcholinesterase (AchE) on conception in dairy cattle during a cloprostenol (prostaglandin F2 alpha analogue, PG)-induced estrus was studied. Malathion (1 mg/kg, intraruminally) given at the onset of estrus (48 h after PG) did not alter the plasma FSH or E2 concentrations but significantly (P less than 0.05) inhibited plasma P4 concentration. The mean P4 concentration in the malathion-treated group on days 8 and 12 were 0.8 +/- 0.4 and 1.0 +/- 0.5 ng/ml, as compared to 2.6 +/- 0.0 and 2.4 +/- 0.3 ng/ml in the control group. There was a nonsignificant (P greater than 0.05) inhibition of plasma AchE activity in malathion-treated cattle. Conception was 16.6% in malathion-treated cows and 50% in controls. Inhibition of progesterone secretion and poor conception occurred after the single intraruminal dose of malathion at the onset of estrus.

The objective of the present study was to evaluate the effects of double uterine flushing on the recovery of embryos/ova in cattle. Two hundred and ten embryo recovery procedures were conducted using a double uterine flushing method, and the results were compared with 432 conventional single-flushing procedures. Cyclic Limousin (n = 403) and Guzera (n = 239) donor cows received an intravaginal progesterone releasing device and 2 mg of estradiol benzoate on Day 0. Between Days 5 and 9, donors received decreasing doses of FSH, which ranged from 200 to 300 IU (Bos indicus) and 300 to 500 IU (Bos taurus). On the afternoon of Day 7, donors received an injection of 500 microg cloprostenol and progesterone implants were removed 12 h later (morning of Day 8). Artificial insemination was performed between 14 and 26 h after first detection of behavioral estrus. Cows were randomly assigned to have embryos recovered by a double-flushing method (n = 210) or the conventional single-flushing procedure (n = 432). For the double-flushing procedure, after first flushing the whole uterus with 1L of Dubelco's Phosphate Buffered Saline (DPBS), a Foley catheter was positioned in the uterine body to permit refilling of the uterus with fresh DPBS (80-150 mL). The catheter was closed with the plunger of a disposable 5 mL syringe, and the donors were allowed to rest in a holding area for 30 min. Thereafter, a second flush was performed to recover the solution remaining in the uterus. Animals from the control group were subjected to a single uterine flush. From 210 double-flushing procedures, 1409 viable embryos were recovered. In comparison, from 432 cows receiving the single-flushing procedure, 1993 embryos were recovered. Double flushing increased (P < 0.05) the number of embryos recovered per procedure compared to single flushing (6.7 +/- 0.4 versus 4.6 +/- 0.2, respectively; mean +/- S.E.M.). When double flushing was performed, average recovered embryos/ova increased (P < 0.05) from 8.3 +/- 0.4 to 12.7 +/- 0.7 in Limousin and from 7.9 to 11.5 in Guzera. Also, utilization of double flushing increased (P < 0.05) the number of viable embryos from 4.7 +/- 0.3 to 6.9 +/- 0.5 in Limousin and from 4.5 +/- 0.4 to 6.4 +/- 0.7 in Guzera. Mean total embryos/ova was similar (P>> 0.05) between the control group and after the first uterine flushing in the double-flushing group; therefore, both flushings were conducted efficiently. In conclusion, double uterine flushing increased embryo recovery in cattle.

The objective of the study was to determine the effects of three dietary energy levels: 0.27 (low level: LL); 0.53 (medium level: ML), and 1.06 (high level: HL) MJMEkg(-1)W(0.75) on estrus synchronization and fertility in Mashona goat does. Forty-five multiparous Mashona goat does of average bodyweight 19.9+/-2.5kg were randomly allocated in equal numbers to the three dietary energy levels. The diets were made from a complete feed ration providing 9.83MJMEkg(-1)DM and 15.5% CPkg(-1)DM. Does were fed initially during a 60-day pre-synchronization period, and blood samples were collected twice a week for the determination of plasma progesterone concentrations to ascertain ovarian activity. Intramuscular injections of cloprostenol (100µg each) were administered 11 days apart. Immediately after the second injection of cloprostenol, three fertile bucks were introduced to the does and were left with the does for 21 days. The does were maintained on their dietary treatments throughout gestation except for those does in the LL treatment. Pregnancy was diagnosed 90 days post-mating using an ultrasound scanner. After pregnancy diagnosis, does on the LL treatment were randomly allocated to ML (n=7) and HL (n=8) treatments. During the pre-synchronization period, does on the LL treatment lost 12.3% whereas those on ML and HL treatments gained 2.1 and 28.8% of their initial bodymasses, respectively. The proportion of does exhibiting overt estrus within 96h after the last cloprostenol injection was significantly lower (P<0.05) for does on the LL treatment (60%) than for those on ML (93%) or HL (100%) treatments, respectively. However, based on plasma progesterone concentrations, the percentage of does on the LL treatment that exhibited ovarian cycles was numerically lower than that of does that were bred (40 versus 73%). Conception, fecundity and twinning rates were significantly lower (P<0.05) on the LL treatment than on the ML and HL treatments. These results indicate that feeding Mashona goat does 0.27MJMEkg(-1)W(0.75) compared to 0.53 and 1.06MJMEkg(-1)W(0.75) reduces the expression of estrus, conception, fecundity and twinning rates, and that feeding 0.53MJMEkg(-1)W(0.75) suffices for optimum reproduction. In addition, the results suggest that cloprostenol administration may induce ovarian cycles in reproductively quiescent does on dietary energy restriction.