We aimed to evaluate the effects and the interaction of size of the preovulatory follicle (POF) and long-acting progesterone (P4) supplementation after timed-AI on CL function and pregnancy success in beef cows. In experiment 1, ovulations of beef cows were synchronized starting on Day -10, and cows were split to receive sodium cloprostenol (large follicle group; LF; n = 31) or nothing (small follicle group; SF; n = 35). Ovulations were induced on Day 0, and cows were inseminated. Ovulated cows were assigned to receive placebo (LF/control group, n = 14; and SF/control group, n = 9) or 150 mg of long-acting P4 on Day 4.5 (LF/P4 group, n = 13; and SF/P4 group, n = 12). Diameter of POF, blood flow in POF wall, ovulation rate, and size and vascularization of CL were greater (P < 0.05) in LF group. In experiments 2 (unknown cyclic status) and 4 (noncycling), ovulations were synchronized, and beef cows received placebo or 150 mg of long-acting P4 on Day 4 after timed-artificial insemination. In experiment 2, pregnancy/AI (P/AI) did not differ (P>> 0.1) between P4-treated (53.2%; 209/393) and control cows (56.2%; 219/390), but P/AI was greater in cows with a CL < 0.9 cm(2) on Day 4 that were P4-treated (57.9%, 22/38) versus placebo-treated (40.4%, 21/52; P < 0.05). In Experiment 4, P/AI was greater (P < 0.05) in P4-treated cows (55.6%, 105/189 vs. 46.0%, 86/187). In Experiment 3, cyclic-suckled beef cows were treated as described in Experiment 1 to generate animals with small (SF; n = 111) or large POF (LF; n = 109), and subdivided to receive placebo or P4 on Day 4. POF size, ovulation rate, CL area, and P/AI were greater (P < 0.007) in the LF group. Pregnancy/AI in ovulated cows were lower (P = 0.05) in the SF/control group (41.5%, 17/41) compared to LF/control group (62%, 31/50) and were similar for the SF/P4 group (55.6%, 25/45) and LF/P4 group (57%, 28/49) compared to others. In summary, smaller and less vascularized POF results in less functional CL and reduces ovulatory rate and P/AI in cyclic beef cows; the long-acting P4 injection on Day 4 after timed-artificial insemination may attenuate the negative effects of small POF/CL; and postovulatory P4 supplementation improved fertility in anestrous beef cattle.

This study examined the effect of a single administration of cephapirin iu or cloprostenol im on the reproductive performance of dairy cows with subclinical endometritis. Cows (n = 228) at 20-33 days in milk (DIM) from two commercial dairy farms, determined to be normal for clinical endometritis (based on absence of abnormal uterine discharge on vaginoscopic examination) were enrolled. At enrollment, a thorough reproductive examination was performed, including rectal palpation, ultrasonography (US) and endometrial cytology (EC). The case definition for subclinical endometritis was the presence of >18% neutrophils on EC examination or fluid in uterus (FIU) on US examination. All cows were randomly assigned to receive one of three treatments: 500 mg benzathine cephapirin iu, 500 microg cloprostenol im, or control (no treatment). Reproductive performance was monitored for a minimum of 8 months after treatment. Cows with subclinical endometritis treated with cephapirin or cloprostenol had a significantly increased relative pregnancy rate compared to control [hazard ratios 1.89 (P = 0.01) and 1.70 (P = 0.05), respectively]. In conclusion, a single treatment with cephapirin or cloprostenol at 20-33 DIM significantly improved the reproductive performance of cows with subclinical endometritis.

Recently, weak estrous behavior was assumed to be the cause of a decline in breeding efficiency in cattle. The present study investigated the effect of measuring the vaginal temperature on the detection of estrus in Japanese Black cows. First, the effect of hormone administration to cows with a functional corpus luteum on the vaginal temperature was evaluated by continuous measurement using a temperature data logger. After 24 h of cloprostenol (PG) treatment, the vaginal temperature was significantly lower than on day 7 after estrus, and the low values were maintained until the beginning of estrus (P < 0.05). The cows that received PG and exogenous progesterone (CIDR) did not show a temperature decrease until the CIDR was removed. This finding suggested that the vaginal temperature change reflected the progesterone concentration. The rate of detection of natural estrus was lower for a pedometer than for the vaginal temperature (P < 0.05); synchronization of estrus resulted in a high estrus detection rate regardless of the detection method. In a subsequent experiment, the effect of vaginal temperature measurement and the use of a pedometer on estrus detection was evaluated in the cool and hot seasons. The average activities during non-estrus and the activity increase ratio (estrus/non-estrus) changed according to season (P < 0.01, P < 0.05). However, the average vaginal temperatures during estrus and non-estrus were not affected by season. The estrus detection rate of the pedometer was lower in summer and lower than that obtained using the vaginal temperature. These results indicated that vaginal temperature measurement might be effective for detecting estrus regardless of estrous behavior.

Experiments were performed to test the hypothesis that there is a negative feedback 'clamp' of ovarian hormones on the hypothalamus and pituitary gland during the follicular phase of the oestrous cycle that limits the secretion of GnRH and LH. GnRH secretion was monitored by sampling the hypophysial portal blood of ewes during the luteal phase of the oestrous cycle and either 24 h or 48 h after the induction of luteolysis by the injection of cloprostenol, a prostaglandin analogue. There was an increase in GnRH pulse frequency in the transition from the luteal to the follicular phase of the cycle. A reduction in the amplitude of GnRH pulses did not occur until 48 h after cloprostenol, suggestive of negative feedback at the level of the hypothalamus that is more profound in the latter part of the follicular phase. The responsivity of the pituitary gland to GnRH was monitored in ewes during the luteal phase of the oestrous cycle and 24 h or 48 h after cloprostenol. Injections of 250 ng or 1000 ng GnRH were given (i.v.) to ewes that had been anaesthetised to suppress endogenous secretion of GnRH and LH. Using the lower dose, the responses 48 h after cloprostenol were not significantly different from those in the luteal phase. With the higher dose of GnRH, a significant (P < 0.05) increase in mean responsivity was seen 48 h after cloprostenol. There was, however, a marked variation in response, with some ewes showing profound increases in LH secretion in response to GnRH and others showing responses that were similar to those obtained during the luteal phase of the cycle. These data are interpreted to mean that the secretion of LH is 'clamped' during the follicular phase of the oestrous cycle and the 'clamp' is only released near the time of the preovulatory LH surge. To test whether or not a rise in GnRH input to the pituitary gland could over-ride the 'clamp' on the pituitary secretion of LH in the late follicular phase of the cycle, sheep were treated 40 h after cloprostenol with either a bolus injection of 500 ng GnRH or four pulses of 125 ng GnRH given at 10-min intervals. These treatments caused small elevations in LH secretion but did not always cause preovulatory LH surges. In some cases, a small rise in LH secretion was induced by GnRH treatments and levels of LH in plasma returned to baseline with the preovulatory LH surge occurring a few hours later.(ABSTRACT TRUNCATED AT 400 WORDS)

The objective of the study was to investigate the light and ultrastructural morphology of dominant and subordinate oocytes from zebu (Bos indicus) cattle. Healthy cycling animals, which had a well-developed corpus luteum as judged by rectal palpation, were administered cloprostenol to induce luteolysis and therefore ovulation. The animals were slaughtered at days 3-11 post-ovulation, but those slaughtered at days 8-11 received a second injection of cloprostenol at day 7. Cumulus-oocyte complexes were aspirated from the largest (dominant) and the second largest (subordinate) follicles, and processed for transmission electron microscopy. Up to day 7, the dominant oocyte presented a peripherally located spherical oocyte nucleus with a compact dense fibrillar nucleolus. After day 7, the nuclear envelope became undulated and the nucleolus vacuolated. The nuclei contained an average of four nucleoli. In addition to vesicles, mitochondria, smooth endoplasmic reticulum, Golgi complexes and cortical granules, the ooplasm contained annulate lamellae and microtubules. Moreover, mitochondrial granules and pleomorphic forms of mitochondria were commonly observed. Some subordinate oocytes exhibited advanced stages of meiotic maturation. It is concluded that (1) the dominant oocyte undergoes certain prematurational changes, including nucleolus vacuolation, in the period from luteolysis up to the presumptive occurrence of the LH peak and (2) subordinate oocytes may undergo meiotic maturation.

The objective of this study was to evaluate two protocols of estrous synchronization in non-lactating Toggenburg goats. Nineteen goats were allocated, according to body condition score and weight, into two groups (A and B) and evaluated utilizing two treatments (T1 and T2). Animals in the T1 and T2 groups received an intravaginal sponge (day 0) containing 60 mg medroxyprogesterone acetate for 6 and 9 days, respectively, plus 200 IU equine chorionic gonadotrophin (eCG) and 22.5 microg cloprostenol 24 h before sponge removal. Females were bred only at the second estrus and received 22.5 microg cloprostenol 7 days later to prevent pregnancy. Percentages of animals in estrus did not differ (P>> 0.05) between T1 (89.5%) and T2 (84.2%). From 33 females in estrus (T1 + T2), 28 (84.8%), 2 (6.1%), and 3 (9.1%) were identified in estrus at 06:00, 12:00 and 18:00 h, respectively. Additionally, 6 (18.2%), 0 (0.0%) and 27 (81.8%) were no longer detected to be on estrus at 06:00, 12:00 and 18:00 h, respectively. Interval from sponge removal and the onset of estrus (IE) did not differ (P>> 0.05) between T1 (46.1 +/- 15.0 h) and T2 (53.6 +/- 16.1 h). Duration of estrus did not differ (P>> 0.05) between T1 (30.0 +/- 12.0 h) and T2 (27.2 +/- 11.2 h). Both protocols were effective in inducing estrus in non-lactating goats. The onset and end of the estrus relative to hour of the day should be considered in estrous detection, natural breeding, and artificial insemination in goats.

Blood oxygen level dependent (BOLD) contrast was used to monitor hypoxia induced by cloprostenol, a prostaglandin F(2alpha) (PGF(2alpha)) analog, in the rat embryo-placental unit (EPU). It is shown that administration of cloprostenol (0.025 mg/rat) at mid-gestation (day 16) reduced EPU oxygenation, as detected by BOLD contrast MRI, in correlation with induction of vascular endothelial growth factor (VEGF) gene (Vegfa) expression in the corresponding placenta (r = 0.56, p = 0.03). Elevated VEGF mRNA expression in response to cloprostenol treatment was also observed at early gestation (day 9) in the forming placenta (p = 0.04) and uterus (p = 0.03). Cloprostenol increased the expression levels of endothelin-1 (ET-1) gene (Edn1) (p = 0.03) and its corresponding peptide (p = 0.02) in the forming placenta, as well as the expression of the endothelin receptor type A (ETA) gene (Ednra) in both the forming placenta (p = 0.009) and the uterus (p = 0.01). The levels of the endothelin receptor type B (ETB) gene (Ednrb) were not affected in response to cloprostenol, but a significant elevation in the expression level of this receptor was observed in the uterus at mid- and late gestation (day 22) (p = 0.04 and 0.01 respectively), suggesting a role for ETB in the vasodilatory status of the pregnant uterus. It is suggested that PGF(2alpha) induces uteroplacental vasoconstriction in the rat, and that ET-1 may take part in mediating this effect, probably via activation of ETA receptor. The uteroplacental vasoconstriction induces hypoxia, as manifested by significant changes in BOLD MRI and by upregulation of VEGF.

The luteolytic response to a prostaglandin F2 alpha analogue, cloprostenol, was investigated in vivo and in vitro at defined stages of the luteal phase. In vivo administration of cloprostenol to female marmoset monkeys on day 3 after ovulation had no effect on plasma progesterone concentrations, whereas administration on day 14 after ovulation reduced plasma progesterone to preovulatory concentrations within 4 h. To identify the cellular basis for this luteolytic action, marmoset luteal tissue obtained on days 3, 6 and 14 after ovulation was incubated in vitro and progesterone production, cAMP accumulation and phosphoinositide (PI) turnover measured in response to cloprostenol, human chorionic gonadotrophin (hCG) with or without cloprostenol, or dibutyryl-cAMP with or without cloprostenol. Progesterone production was stimulated by both hCG and dbcAMP at all stages of the luteal phase. Although neither hCG nor dbcAMP had any significant effects on PI turnover, hCG also increased cAMP accumulation. In marmoset luteal tissue obtained on day 3 after ovulation, cloprostenol had no significant effect on basal or hCG/dbcAMP-stimulated progesterone production but significantly stimulated PI turnover. In contrast, on days 6 and 14 after ovulation, cloprostenol significantly inhibited hCG- and dbcAMP-stimulated progesterone production and the cAMP response to hCG, but had no significant effect on PI turnover. Since progesterone production by the marmoset corpus luteum depends on the luteotrophic support of luteinizing hormone (LH), these observations suggest that the luteolytic action of cloprostenol in vivo involves the inhibition of LH/hCG action at sites both prior and subsequent to cAMP accumulation. However, such luteolytic effects do not appear to require the generation of inositol phosphates by increased PI turnover.

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

Progesterone concentrations in the milk of 86 Friesian cows induced to superovulate with an FSH-Cloprostenol treatment were studied daily from the day of estrus (D 0) to Day 7 (D 7). From D 2, a significant correlation between progesterone concentrations and ovulation rate was observed. Such a relationship was also observed beginning to D 3 between progesterone concentrations and the number of embryos recovered. No relationship was found between progesterone content and the number of viable embryos. For 30 of these cows, progesterone concentrations in blood plasma were also studied. The hormonal patterns in plasma and milk were similar but quantitative relationships were demonstrated earlier for progesterone in plasma than for progesterone in milk. It is concluded that relationships between milk progesterone concentrations and ovarian responses to a superovulatory treatment exist and could be of interest in embryo transfer programs in when predicting the number of embryos to be recovered.

Cumulative concentration-effect curves for prostaglandin E(2), sulprostone and butaprost were constructed in matched strips of human non-pregnant myometrium from 14 different donors. All samples were obtained from the mid-lateral wall of the uterus. Prostaglandin E(2) produced four types of concentration-effect curves: monophasic inhibitory (n = 7), monophasic excitatory (n = 2), biphasic consisting of an excitatory phase followed by an inhibitory phase (n = 4), and biphasic consisting of an inhibitory phase followed by an excitatory phase (n = 1). Sulprostone produced excitation of spontaneous contractile activity in all tissues (mean pEC(50) = 9.1+/-0.2, range 8.1-10.1, n = 14). Butaprost produced relaxation of cloprostenol-stimulated contractile activity in all tissues (mean pEC(50) = 5.7 +/- 0.1, range 5.0-6.9, n = 14). The mean pEC(50) value for sulprostone was significantly higher in tissues where prostaglandin E(2) caused some excitation (pEC(50) = 9.4 +/- 0.2, n = 7) compared to those where prostaglandin E(2) caused only inhibition (pEC(50) = 8.8 +/- 0.2, n = 7). Mean pEC(50) values for butaprost were not significantly different between these groups. These data suggest that (a) variability in EP receptor-mediated responses exists within a single anatomical site; (b) both excitatory and inhibitory EP receptor-mediated pathways are always operative in human non-pregnant myometrium, regardless of the type of tissue response to prostaglandin E(2); and (c) regulation of EP receptor-mediated responses occurs predominantly in the excitatory (EP(3) or EP(1) receptor) pathway rather than the inhibitory (EP(2) receptor) pathway.

Path analysis was used to determine the interrelationships between postpartum administration of gonadotrophin releasing hormone and cloprostenol and the occurrence of reproductive disease and reproductive performance in dairy cows. The data analysed were those collected on 226 Holstein-Friesian cows calving in a commercial dairy herd during a 17 month period (May 1, 1981 to October 1, 1982). Cows administered gonadotrophin releasing hormone at day 15 postpartum experienced an improved rate of uterine involution as determined by rectal palpation nine days later. Although this improved rate of uterine involution reduced the risk of pyometritis, it actually directly delayed conception. Also, gonadotrophin releasing hormone therapy directly resulted in an increased incidence of pyometritis which in turn resulted in an increase incidence of cystic ovarian disease and anestrus. The occurrence of these abnormalities resulted in increased intervals from calving to first observed estrus, first service and conception. In addition to this effect, the administration of gonadotrophin releasing hormone was also associated with increased plasma progesterone concentrations at days 24 and 28 postpartum which delayed conception. Cloprostenol therapy at day 24 postpartum resulted in a decreased plasma progesterone concentration at day 28 postpartum which was directly and indirectly associated with a decrease in the calving to conception interval. The indirect effects were mediated by a reduction in days to first estrus. Cloprostenol therapy also directly resulted in a decreased calving to first observed estrus interval for reasons not attributable to the level of progesterone at day 28.

PRL and placental lactogen (PL) play key roles in maintaining the rodent corpus luteum through pregnancy. Suppressors of cytokine signaling (SOCS) have been shown to decrease cell sensitivity to cytokines, including PRL, and so here we have addressed the issue of whether luteolysis induced by prostaglandin F(2alpha) (PGF(2alpha)) might up-regulate SOCS proteins to inhibit PRL signaling. In d 19 pregnant rats, cloprostenol, a PGF(2alpha) analog, rapidly induced transcripts for SOCS-3 and, to a lesser extent, SOCS-1. We also found increased SOCS-3 protein in the ovary by immunoblot and in the corpus luteum by immunohistochemistry. Increased SOCS-3 expression was preceded by an increase in STAT3 tyrosine phosphorylation 10 min after cloprostenol injection and was maintained for 4 h, as determined by gel shift and immunohistochemistry. Induction of SOCS-3 was accompanied by a sharp decrease in active STAT5, as determined by gel-shift assay and by loss of nuclear localized STAT5. Four hours after cloprostenol administration, the corpus luteum was refractory to stimulation of STAT5 by PRL administration, and this was not due to down-regulation of PRL receptor. Therefore, induction of SOCS-3 by PGF(2alpha) may be an important element in the initiation of luteolysis via rapid suppression of luteotropic support from PL.

The chirality of drugs, with particular reference to agents used in veterinary medicine, is reviewed. Basic concepts of chirality and aspects of the methodology for the separation of enantiomers are considered. Chiral compounds are in common use in animals and their pharmacological actions and side-effects (pharmacodynamics) and absorption into and fate within the body (pharmacokinetics) are of fundamental importance; pharmacodynamic and pharmacokinetic properties of enantiomeric pairs commonly differ and this has major implications for their effective and safe therapeutic use. As examples of the particular significance of chirality in veterinary medicine, the following drug classes are reviewed; benzimidazole anthelmintics, cloprostenol, verapamil, ketamine, halogenated hydrocarbon anaesthetics and 2-arylpropionic acid anti-inflammatory drugs. The implications of chirality for drug product development and approval by registration authorities are discussed.

We have suggested in a previous in vitro study that tumor necrosis factor-alpha (TNFalpha) plays a role in the initiation of luteolysis in cattle. The aim of the present study was to examine the influence of different doses of TNFalpha on the estrous cycle in cattle by observing the standing behavior and measuring peripheral concentrations of progesterone (P4) during the estrous cycle. Moreover, we evaluated the secretion of P4, oxytocin (OT), nitric oxide (NO), and luteolytic (prostaglandin F2alpha [PGF2alpha] and leukotriene C4 [LTC4]) and luteotropic (PGE2) metabolites of arachidonic acid in peripheral blood plasma as parameters of TNFalpha actions. Mature Holstein/Polish black and white heifers (n = 36) were treated on Day 14 of the estrous cycle (Day 0 = estrus) by infusion into the aorta abdominalis of saline (n = 8), an analogue of PGF2alpha (cloprostenol, 100 microg; n = 3) or saline with TNFalpha at doses of 0.1 (n = 3), 1 (n = 8), 10 (n = 8), 25 (n = 3), or 50 microg (n = 3) per animal. Peripheral blood samples were collected frequently before, during, and up to 4 h after TNFalpha treatment. After Day 15 of the estrous cycle, blood was collected once daily until Day 22 following the first estrus. Lower doses of TNFalpha (0.1 and 1 microg) decreased the P4 level during the estrous cycle and consequently resulted in shortening of the estrous cycle (18.8 +/- 0.9 and 18.0 +/- 0.7 days, respectively) compared with the control (22.3 +/- 0.3 days, P < 0.05). One microgram of TNFalpha increased the PGF2alpha (P < 0.001) and NO (P < 0.001) concentrations and decreased OT secretion (P < 0.01). Higher doses of TNFalpha (10, 25, 50 microg) stimulated synthesis of P4 (P < 0.001) and PGE2 (P < 0.001), inhibited LTC4 secreton (P < 0.05), and consequently resulted in prolongation of the estrous cycle (throughout 30 days, P < 0.05). Altogether, the results suggest that low concentrations of TNFalpha cause luteolysis, whereas high concentrations of TNFalpha activate corpus luteum function and prolong the estrous cycle in cattle.

Factor XI (F XI) deficiency is an autosomal recessive coagulopathy found in Holstein cattle. Affected animals have a 50% greater prevalence of repeat breeding. Therefore, several parameters describing ovarian function were studied. Daily blood sampling revealed that progesterone concentrations were slower to decline from a peak at day 16 (p < 0.01) to values less than 3 nmol/L in F XI-deficient cows (5.14 +/- 0.69 days (mean +/- SD) versus 4.05 +/- 0.63 days in control animals), resulting in an oestrous cycle length of 24.7 +/- 2.1 days compared to 22.9 +/- 3.0 days, respectively. This was not due to an alteration in the availability of prostaglandin F2 alpha (PGF2 alpha) or oxytocin (OT) involved in luteolysis. No significant differences (p>> 0.05) were seen between normal (n = 7) and F XI-deficient (n = 7) cows in the peak values or the area under the curve for the pulse in 13,14-dihydro-15-keto PGF2 alpha in response to OT challenge or in the parameters describing the pulse of ovarian OT secretion after PGF2 alpha injection (n = 7 for each) between days 12 and 14. Ovulatory follicular development was assessed by ultrasound monitoring and plasma 17 beta-oestradiol values at 8-h intervals after a luteolytic injection of cloprostenol (n = 6 for each). Follicular diameter was smaller (p < 0.05) and accompanied by lower peak oestradiol values near the time of ovulation in F XI-deficient cows. The results suggest that the oestrous cycle in F XI-deficient cows is characterized by a slower process of luteolysis that may be associated with smaller follicular development.

The objective of this study was to compare 2 surrogate vaginal examination methods (i.e., gloved hand and a vaginal device) with vaginoscopy as a reference method for diagnosing clinical endometritis in dairy cows. Holstein-Friesian cows (n = 1,002) in 2 commercial dairy herds in Germany were examined for endometritis at 21 to 27 d in milk (DIM) by using 1 of 3 vaginal diagnostic methods. Vaginal examinations were performed either with a speculum (reference method), a vaginal device (Metricheck, Simcro, New Zealand), or a gloved hand. Vaginal discharge adhering to the diagnostic tool was classified according to a vaginal discharge score ranging from 0 to 3 (where 0 = translucent mucus, 1 = mucus containing flecks of white or off-white pus, 2 = less than 50% white or off-white mucopurulent material, and 3 = greater than 50% white or yellow pus that may be sanguineous). Cows with vaginal discharge scores of 1 to 3 received 500 microg of cloprostenol after examination and again 14 d later (35 to 41 DIM). The prevalence of endometritis in both herds was 40.6 and 40.3%, respectively. With the Metricheck device, significantly more cows were diagnosed as affected with endometritis than by examination with a speculum or a gloved hand (47.5 vs. 36.9 and 36.8%). Binary logistic regression for the risk of conception after first AI as an outcome variable, with vaginal discharge score, diagnostic method, and farm as covariates, revealed a significant effect of degree of endometritis, but not of the diagnostic methods. Survival analyses for the hazard of insemination and pregnancy within 200 DIM, respectively, revealed a significant effect of degree of endometritis, herd, and parity, but not of the diagnostic tool. It can be concluded that any one of the 3 vaginal examination methods can be used interchangeably, without a negative effect on reproductive performance.

Luteal regression is initiated by prostaglandin F(2 alpha) (PGF(2 alpha)). In domestic species and primates, demise of the corpus luteum (CL) enables development of a new preovulatory follicle. However, during early stages of the cycle, which are characterized by massive neovascularization, the CL is refractory to PGF(2 alpha). Our previous studies showed that endothelin-1 (ET-1), which is produced by the endothelial cells lining these blood vessels, plays a crucial role during PGF(2 alpha)-induced luteolysis. Therefore, in this study, we compared the effects of PGF(2 alpha) administered at the early and mid luteal phases on ET-1 and its type A receptors (ETA-R) along with plasma ET-1 and progesterone concentrations, and the mRNA levels of PGF(2 alpha) receptors (PGF(2 alpha)-R) and steroidogenic genes. As expected, ET-1 and ETA-R mRNA levels were markedly induced in midcycle CL exposed to luteolytic dose of PGF(2 alpha) analogue (Cloprostenol). In contrast, neither ET-1 mRNA nor its receptors were elevated when the same dose of PGF(2 alpha) analogue was administered on Day 4 of the cycle. In accordance with ET-1 expression within the CL, plasma ET-1 concentrations were significantly elevated 24 h after PGF(2 alpha) injection only on Day 10 of the cycle. The steroidogenic capacity of the CL (plasma progesterone as well as the mRNA levels of steroidogenic acute regulatory protein and cytochrome P450(scc)) was only affected when PGF(2 alpha) was administered during midcycle. Nevertheless, PGF(2 alpha) elicited certain responses in the early CL: progesterone and oxytocin secretion were elevated, and PGF(2 alpha)-R was transiently affected. Such effects probably result from PGF(2 alpha) acting on luteal steroidogenic cells. These findings may suggest, however, that the cell type mediating the luteolytic actions of PGF(2 alpha), possibly the endothelium, could yet be nonresponsive during the early luteal phase.

Stillbirth in swine ranges from 2 to 9%, resulting in a significant loss of piglets. Previous studies clearly indicate a relationship between prolonged birth intervals and stillbirth, but factors influencing birth intervals are not fully known. To characterize birth intervals and stillbirth, farrowing was recorded during three farrowing seasons. Blood samples were collected on d 110 and d 113 of gestation, and were assayed for progesterone and estrogen. Relationships between estrumate (cloprostenol sodium, an analogue of prostaglandin F(2alpha)) usage, litter size, proportion of the litter farrowed, progesterone and estrogen concentrations, birth intervals, and stillbirth were analyzed using regression analysis. A clear relationship between birth intervals and stillbirth was observed. Stillbirth rate was unaffected by birth intervals of <1 h, and increased (P < 0.01) for birth intervals >1 h. A significant negative association between litter size and birth intervals was observed (P < 0.01). Birth intervals were unaffected by proportion of the litter farrowed until the last piglet in the litter, whose birth interval increased dramatically (1.5-fold; P < 0.01). Stillbirth rates increased as proportion of the litter farrowed increased, and a dramatic increase in stillbirth occurred for the last piglet in the litter. Neither d 110 nor 113 plasma progesterone concentrations were associated with litter size, birth intervals, or stillbirth rates. Curvilinear relationships were present between d 110 or 113 plasma estradiol concentrations and litter size. However, neither d 110 nor 113 estradiol concentrations were associated with birth intervals or stillbirth rates. These results indicate that (1) birth intervals greater than 1 h are associated with increased stillbirth; (2) larger litter size reduces birth intervals; (3) the last piglet in the litter has both a prolonged birth interval and increased risk of stillbirth; (4) plasma progesterone before farrowing does not influence birth intervals or stillbirth; and (5) plasma estradiol does not influence birth interval or stillbirth, despite a positive relationship between litter size and plasma estradiol. An understanding of the effects of litter size and proportion of the litter farrowed on birth intervals might be exploited to decrease stillbirth in piglets.

Four consecutive experiments were conducted to design and establish the effectiveness of different protocols for induction and synchronization of oestrus and ovulation in mice. Results showed that the highest synchronization degree and the highest fertility rates were obtained using two intraperitoneal doses of 0.5 microg of cloprostenol, three days apart, plus a single subcutaneous dose of 3 microg of progesterone coincidentally with the first injection of cloprostenol. Of the main advantages of the new method, we have to highlight the short time elapsed for appearance, and the high degree of synchronization of oestrus and ovulations (almost 100% of the animals responding to the treatment in 48 h; 78.4% with fertile mates at 24 h), plus the high fertility rate obtained after a programmed mating (100%). Overall, these yields are superior to those obtained by classical methods based on the use of male pheromones; hence the proposed protocol arises as an adequate alternative for reproductive management in mice.

Indomethacin (INDO, n = 5) or vehicle (CONTROL, n = 4) was injected into superovulated heifers at 48 and 60 h following a luteolytic cloprostenol injection (0 h). One heifer from each group was ovariectomized (OVX) at 48, 56, 64 and 72 h. The fifth heifer of the INDO group was OVX at 80 h. Blood samples were collected at 0 h, every 2 h between 37 and 47 h, and at the time of each OVX to monitor plasma progesterone (P4) and luteinizing hormone (LH) concentrations. Following each OVX, the number and size of follicles were recorded and the incidence of ovulation determined. Follicular fluid (FF) was aspirated from follicles greater than or equal to 8 mm to determine the concentration of prostaglandins E2 (PGE2) and F2 alpha (PGF2 alpha). The highest PG concentrations were measured in both groups at 24-25 h following the preovulatory LH surge and the PGF2 alpha concentration at this time was significantly greater (p less than 0.01) in the CONTROL group compared to the INDO group. By 35-36 h after the LH surge, 75% (25/34) of the CONTROL follicles had ovulated, whereas there were no ovulations (0/50) on either ovary of the INDO treated heifer. These preliminary results suggest that the preovulatory rise of PGs in FF, particularly PGF2 alpha, is essential for ovulation and that suppression of this rise with indomethacin will inhibit ovulation in heifers.

Actinomyces pyogenes from a case of endometritis was used to study the effects of infection of the bovine embryo between days 27 and 41 of pregnancy. From 10(9) to 10(10) washed organisms were introduced into the uterine lumen of four pregnant cows. Two pregnant cows were inoculated with sterile saline and four pregnant cows were treated with cloprostenol. Embryonic death and abortion followed 29 to 144 hours after the inoculation of the live bacteria. The aborted embryos were macerated or clearly degenerating and yielded profuse pure cultures of A pyogenes. Abortion was accompanied by a sustained increase in uterine tone, opening of the cervix, presence of vaginal pus and a vulval discharge and the persistence of the corpus luteum for at least eight days after abortion. Intrauterine inoculation with saline did not affect pregnancy, but embryonic death, abortion and regression of the corpus luteum occurred 66 to 72 hours after the treatment with cloprostenol. The results suggest that A pyogenes is a primary pathogen and is capable of causing embryonic death and abortion.

An experiment was conducted in order to determine the pattern of, and the relationships between, the secretion of inhibin, estradiol, and androstenedione by the ovary and the concentration of LH, FSH, and PRL during the estrous cycle of sheep. The estrous cycles of 6 Finn-Merino ewes in which the left ovary had been autotransplanted to the neck were synchronized by two injections of cloprostenol (100 micrograms im) a potent analog of prostaglandin F2 alpha (PG) given 14 days apart. The ewes had ovarian and jugular venous blood samples taken at four hourly intervals from 42 h before the second PG injection until day 6 of the following cycle. All animals responded to PG with the preovulatory LH surge occurring within 58 +/- 2 h (mean +/- SEM). The concentration of FSH in jugular venous plasma fell (P less than 0.001) after the induction of luteolysis and then exhibited 3 peaks, the first coincident with the LH surge, the second on day 1, and the third on day 6. After injection of PG the secretion rates of inhibin, estradiol, and androstenedione increased (P less than 0.05) within 4-8 h. After this increase in the early follicular phase the secretion rate of estradiol continued to rise until the time of the LH surge (P less than 0.001). Although the secretion of androstenedione and inhibin increased in the 36 h before the LH surge the magnitude of this rise was less marked than for estradiol and was not statistically significant. Within 4-8 h of the start of the LH surge the secretion of estradiol and androstenedione declined rapidly reaching barely detectable levels within 16 h (P less than 0.001). In contrast the secretion of inhibin increased after the LH surge reaching a broad peak (P less than 0.05) of approximately 16-h duration, coincident with the second peak of FSH. From days 2-6 mean secretion of inhibin remained relatively stable at 2-6 ng/min although considerable variation was observed in individual profiles. The rate of estradiol secretion increased steadily from its nadir on day 1 to a broad peak centered around day 3 (3-6 ng/min, P less than 0.001) followed by a decline until by day 6 the estradiol secretion rate was less than 1 ng/min (P less than 0.01). The secretory profile for PRL showed a close relationship with estradiol secretion.(ABSTRACT TRUNCATED AT 400 WORDS)

This study examines differences in intracellular responses to cloprostenol, a prostaglandin (PG)F(2alpha) analog, in porcine corpora lutea (CL) before (Day 9 of estrous cycle) and after (Day 17 of pseudopregnancy) acquisition of luteolytic capacity. Pigs on Day 9 or Day 17 were treated with saline or 500 microgram cloprostenol, and CL were collected 10 h (experiment I) or 0.5 h (experiment III) after treatment. Some CL were cut into small pieces and cultured to measure progesterone and PGF(2alpha) secretion. In experiment I, progesterone remained high and PGF(2alpha) low in luteal incubations from either Day 9 or Day 17 saline-treated pigs. Cloprostenol increased PGF(2alpha) production 465% and decreased progesterone production 87% only from Day 17 luteal tissue. Cloprostenol induced prostaglandin G/H synthase (PGHS)-2 mRNA (0.5 h) and protein (10 h) in both groups. In cell culture, cloprostenol or phorbol 12, 13-didecanoate (PDD) (protein kinase C activator), induced PGHS-2 mRNA in luteal cells from both groups. However, acute cloprostenol treatment (10 min) decreased progesterone production and increased PGF(2alpha) production only from Day 17 luteal cells. Thus, PGF(2alpha) production is induced by cloprostenol in porcine CL with luteolytic capacity (Day 17) but not in CL without luteolytic capacity (Day 9). However, this change in PGF(2alpha) production is not explained by a difference in induction of PGHS-2 mRNA or protein.