Steroid concentrations in cows with corticotropin-induced cystic ovarian follicles and the effect of prostaglandin F2alpha and indomethacin given by intrauterine injection.

In 7 instances, cystic ovarian follicles resulted when adrenocorticotropin (ACTH) was administered daily during the follicular phase of the estrous cycle in cows. Two cows given daily injections of hydrocortisone (cortisol) during the follicular phase of the estrous cycle did not develop cystic ovaries. Plasma concentrations of estradiol in cows with induced cystic ovarian follicles were similar to the peak values observed at estrus and were between 6 and 12 pg/ml. Progesterone concentrations in plasma of cows with cystic ovaries were low, between 1 and 2 ng/ml. Ovulation occurred when 2 cows were given human chorionic gonadotropin (HCG) during the period of ovarian cyst development with ACTH administration. Several days of administration of ACTH was required to cause cyst development. Ovulation occurred at the expected time in 1 cow when injections began on day 19, that is, late in the follicular period. In another cow, when treatment was stopped on day 3, after the expected time of estrus a delayed ovulation occurred. In 2 cows with induced cystic ovarian follicles, cyst atresia occurred spontaneously about day 13 to 17 of the cycle. In these cows, new follicular growth and ovulation followed (although delayed in 1 cow). The time of atresia of cystic follicles was not influenced by the intrauterine injection of 10 ml of sterile saline solution on days 8, 9, and 10 in 1 cow. When 5 mg of prostaglandin F2alpha in 10 ml of sterile saline solution was given (uterine injection) in 2 cows on days 8, 9, and 10, cyst atresia occurred earlier than the time of spontaneous atresia. Intrauterine administration of 100 mg of indomethacin in 10 ml of sterile saline solution daily for 13 or 14 days to 2 cows, starting on day 12 or 13 of the cycle, resulted in persistence of the induced cystic ovarian follicles. After cessation of indomethacin treatment, atresia of cysts followed and new follicular growth and ovulation occurred.     

Effect of prostaglandin F2 alpha on hormone concentrations in dairy cows after parturition

This study was designed to evaluate the effects of exogenous prostaglandin F2 alpha (PGF2 alpha) on hormone secretion in cows without a corpus luteum. Blood samples were taken from 10 Friesian dairy cows at frequent intervals from a jugular vein and the caudal vena cava starting between nine and 20 days after parturition. PGF2 alpha (25 mg dinoprost) was injected intramuscularly into five cows after the first eight hours of sampling. Plasma concentrations of 13,14-dihydro 15-keto PGF2 alpha (PGFM) increased rapidly but had returned to baseline by 14 hours after injection. There was no significant effect of the treatment on the time taken by the cows to resume ovarian cycles, and it had no consistent effect on plasma luteinising hormone (LH) patterns; however the amplitude of pulses of LH was temporarily suppressed in two cows and the frequency of pulses of LH was immediately increased in one cow. Treatment with PGF2 alpha had no significant effect on the concentration of oestradiol in blood from the vena cava. It is concluded that any enhancement of the reproductive performance of cows treated with PGF2 alpha after parturition is not due to a direct effect on pituitary-ovarian function.     

Lactation and fertility in goats after the induction of parturition with an analogue of prostaglandin F2 alpha, cloprostenol

Cloprostenol, 100 micrograms, given intramuscularly to the nanny, with 50 micrograms 10 hours later, precipitated parturition in goats after 36 +/- 1 hours (mean +/- SEM), when administered at 137 +/- 0.5 days gestation. All kids were born alive and survived to weaning. Milk yield over 40 weeks post partum was not significantly different from that after spontaneous parturition. Three hundred micrograms cloprostenol (200 micrograms with 100 micrograms 10 hours later) also initiated parturition at 137 +/- 0.5 days gestation but caused a significant (P less than 0.01) suppression of lactation. Cloprostenol-induced parturition in more than one pregnancy had no adverse effects except for an increased incidence of placental retention, which was treated successfully with intrauterine pessaries containing oestrogen. During the first eight days after spontaneous parturition efficiency of milk secretion was inversely related to udder mass, suggesting a gradual maturation of the secretory alveolar epithelium over this time. When parturition was induced by cloprostenol there was a four to eight day delay before the establishment of this relationship which appeared essential for a successful lactation. Cloprostenol proved to be a useful tool for the control of parturition in goats, having applications to both general animal husbandry and for the study of mammary development and secretory competence.     

Arginine vasopressin stimulation of prostaglandin F2 alpha release in heifers during the estrous cycle

The effect of arginine vasopressin on the stimulation of prostaglandin F2 alpha (PGF2 alpha) release has been examined in vivo. Fifty-eight heifers received one intravenous injection of 10 IU arginine vasopressin on either Day 0 (n = 14), Day 6 (n = 12), Day 13 (n = 14) and Day 18 or 19 or 20 (Day 18-20, n = 18) after the onset of oestrus (Day 0) to determine the effect of arginine vasopressin at different times of the oestrous cycle. Frequent blood samples were taken before and after arginine vasopressin injection for the measurement of 13,14-dihydro-15-keto-PGF2 alpha (PGFM) by radioimmunoassay (RIA). Blood samples for progesterone determinations were taken 2 hr before and 24 hr after arginine vasopressin to monitor luteal function. The data show that arginine vasopressin causes an increase (P less than 0.005) in PGFM concentrations only at Day 18-20 of the cycle in 67% of the experimental heifers.     

Effect of prostaglandin F2alpha on ovarian, adrenal, and pituitary hormones and on luteal blood flow in mares

The effect of a single injection of prostaglandin F2alpha (PGF) during mid-diestrus on systemic concentrations of progesterone, LH, FSH, estradiol, and cortisol and on blood flow to the corpus luteum was studied in 10 controls and 10 PGF-treated mares. Blood flow was assessed by estimating the percentage of corpus luteum with color-Doppler signals of blood flow during real-time scanning of the entire structure and by the diameter of the vascular pedicle near its attachment to the ovary. Treatment was done 8 days after ovulation and 0 h was immediately before the treatment. Examinations and collection of blood samples were done at 0 h, every 5 min until 1h, and then at 1.5, 2, 4, 8, 12, 24, 48, and 72 h. The concentrations of estradiol did not change, but progesterone, LH, FSH, and cortisol increased significantly within 5 min. Concentrations of LH and FSH in the PGF group remained elevated until a temporarily lower concentration at 8 or 4h, respectively, rebounded to 12h, and then slowly decreased. Cortisol remained elevated, until a decrease between 1 and 4h. Progesterone in the PGF group increased significantly until 10 min after 0 h and then decreased by 40 min to below the concentrations in controls. Within the PGF group, progesterone decreased significantly by 45 min to below the concentrations at 0 h. The values for each of the two indicators of blood flow did not differ significantly between the PGF and control groups until a decrease at 24h in the PGF group. Results did not support the hypothesis that the immediate transient post-PGF increase in progesterone was associated with an increase in luteal blood flow. Luteolysis, as indicated by decreasing progesterone, began well before the beginning of a decrease in luteal blood flow.     

Endogenous prostaglandin F2 alpha release induced by physiologic saline solution infusion in utero in the mare: effect of temperature, osmolarity, and pH

Thirty mares with normal estrous cycles were allotted equally to 5 groups and infused with 250 ml of saline (NaCl) solution in utero on the seventh day after ovulation to test the effects of temperature, osmolarity, or pH of the saline solution on prostaglandin F2 alpha (PGF2 alpha) release and luteolysis. Intrauterine infusion of phosphate-buffered saline solution failed to alter the duration of the luteal phase, compared with the control group. Similarly, increasing the temperature of phosphate-buffered saline solution to 42 C or increasing (600 mosm) or decreasing osmolarity (less than 10 mosm) did not change the duration of the luteal phase. Decreasing the pH of saline solution to 3 caused significant (P less than 0.0001) releases of PGF2 alpha from the uterus within the first hour after infusion, and the luteal phase was shortened to 8.8 +/- 1.0 days (mean +/- SEM; control, 15 +/- 1.2 days). The results of this study showed that pH is the main factor in eliciting PGF2 alpha release by intrauterine infusion of a saline solution, whereas increased temperature and osmolarity have no effect on the release of PGF2 alpha. The intrauterine infusion of sterile water or physiologic saline (NaCl) solution has been used to induce estrus in mares for the past 50 years. Many investigators have reported that intrauterine infusion of physiologic saline solution or water at body temperature (37 C) or warmer up to 45 C) causes most "anestrous" mares to return to estrus in 1 to 8 days.(ABSTRACT TRUNCATED AT 250 WORDS)     

The effect of estrogen, progesterone and prostaglandin F2 alpha on uterine contractions in seasonally anovulatory mares

Uterine contractions were studied in two experiments utilizing ultrasonography and seasonally anovulatory mares. A one-minute ultrasound scan was done to produce longitudinal real-time images of the uterine body and an overall uterine contractile activity score (0 = no or minimal activity to 4 = maximal activity) was assigned to each scan. In experiment 1, a two-hour uterine activity trial (one score every 10 minutes) was done in mares given a single injection of prostaglandin F2 alpha (PGF2 alpha group; n = 4) and in control mares (n = 4). There was no difference between the two groups over the two-hour trial (mean activity score averaged over the two-hour trial: PGF2 alpha group, 0.2; control group, 0.1). In experiment 2, 16 mares were randomly assigned to one of four groups: 1) controls (corn oil vehicle), 2) 1 mg estradiol 17 beta on days 0 to 9 and 100 mg progesterone on days 10 to 20 (E2--greater than P4 group), 3) 100 mg progesterone on days 0 to 20 (P4 group), and 4) 100 mg progesterone on days 0 to 9 and 1 mg estradiol 17 beta + 100 mg progesterone on days 10 to 20 (P4--greater than E2 + P4 group). Uterine activity was assessed for each mare daily. The day by group interaction was significant. Scores for the E2--greater than P4 group were greater on days 4 to 11 (P less than .05) than for the other three groups. From day 14 to 21, scores did not differ among the three steroid-treated groups (except on day 15), but the scores averaged over each steroid-treated group were greater for each day (P less than .1 or .05) than for the controls (except on day 17).(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of various veterinary procedures on plasma concentrations of cortisol, luteinising hormone and prostaglandin F2 alpha metabolite in the cow

Five commonly practised veterinary procedures were studied: Palpation per rectum of the reproductive tract, intramuscular injection, single venepuncture, repeated venepuncture and jugular vein catheterisation. Plasma cortisol concentrations increased from baseline values of approximately 2 ng/ml to maximum mean values between 6.5 +/- 2.5 ng/ml and 13.8 +/- 5.6 ng/ml approximately 13 to 27 minutes after each manipulation. Baseline values occurred approximately 80 minutes later. In the control bleeding periods unacclimatised cows initially had high values of plasma cortisol (5 to 10 ng/ml) which returned to baseline after two hours, ie, before beginning any procedure. There were no statistically significant changes in luteinising hormone concentrations. The concentration of 13,14 dihydro, 15-keto prostaglandin F2 alpha (PGFM) increased from 61.0 +/- 4.6 pg/ml to 209.8 +/- 152.1 pg/ml in three out of five cows palpated on days 16 and 19 of the oestrous cycle. Increases did not occur in five other cows palpated during the follicular phase, nor in five cows palpated on day 12. However, after palpation on day 8, one animal did have concentrations of PGFM similar to those occurring during spontaneous release on days 18 to 20 of the oestrous cycle.     

Plasma fatty acids, prostaglandin F2alpha metabolite, and reproductive response in postpartum heifers fed rumen bypass fat

An experiment was conducted to determine whether feeding rumen-protected fatty acids (FA) to postpartum heifers would increase plasma concentrations of linoleic acid and PGF2, metabolite (PGFM), shorten the interval from calving to first increase in plasma concentrations of progesterone (P4), and increase pregnancy rate relative to controls. Hereford x Angus heifers (346 kg) were assigned randomly to treatments containing either lipid or barley supplemented diets for the first 30 d postpartum. Lipid was .23 kg.heifer(-1).d(-1) of calcium salts of FA (CSFA; n = 20), and an isocaloric amount of barley served as the control (n = 19). Supplements, with .23 kg of barley as a vehicle, and a basal diet of meadow and alfalfa hays were pen fed to heifers (5/pen). Heifers were bled on alternate days (d1 to 30) and twice weekly (d 30 to 2 wk after first estrus) for RIA of plasma PGFM and P4, respectively. Weight percentage of major FA in plasma on d1 and 7 was determined with gas chromatography. First behavioral estrus was detected by use of intact bulls and confirmed by an increase in plasma P4. On d 7, but not d 1, plasma from heifers fed CSFA had altered proportions of major FA (P < .01), including an increase in linoleic acid compared with those of controls (29.1 vs 25.6% of total FA; SE = .75; P < .01). Analysis of variance of contrast variables revealed an effect of treatment on direction of change in PGFM from d 3 to 5 (P < .01). By d 7 and on d 9, plasma concentrations of PGFM were greater in heifers fed CSFA than in controls (P = .02 and P = .06, respectively). There was no difference in plasma concentration of PGFM between treatments on d 1, 3, 5, 11, 13, and 15 postpartum (P = .80, .17, .52, .82, .46, and .77, respectively). Days to first estrus with ovulation, pregnancy rate, and calving interval were not affected by treatments (P = .58, .52, and .24, respectively). Although supplemental lipid fed to primiparous beef heifers increased plasma levels of linoleic acid and production of PGFM in the early postpartum period, it did not improve the fertility of these heifers in the subsequent breeding season.     

Plasma luteinizing hormone and progesterone concentrations in goats with estrous cycles of normal or short duration after prostaglandin F2 alpha administration during diestrus or pregnancy

Plasma luteinizing hormone (LH) and progesterone concentrations were compared in does experiencing short-duration estrous cycles and in does with estrous cycles of normal duration. The short-duration estrous cycles were observed immediately after induction of abortion in pregnant does by use of prostaglandin (PG) F2 alpha. Intramuscular administration of 5 mg of PGF2 alpha was accomplished in 8 does that were 52 to 63 days into gestation and in 9 cycling does at 7 to 10 days after estrus. In both groups, the mean plasma concentration of progesterone decreased from a luteal phase concentration immediately before to less than 1 ng/ml by 24 hours after PGF2 alpha administration. Of the 8 does that aborted, 6 experienced short-duration estrous cycles, and 4 of these 6 had an LH surge during the time of blood sample collection. The mean time from PGF2 alpha administration to the LH surge was significantly (P less than 0.05) longer in does with short-duration estrous cycles (71 hours) than that in does with estrous cycles of normal duration (58 hours). The mean area under the LH concentration curve was significantly (P less than 0.005) less for does with short-duration estrous cycles. Short-duration estrous cycles were associated with delayed preovulatory LH surges of reduced magnitude.     

Effect of PGF2 alpha administration on the release of endogenous PGF2 alpha and oxytocin in indomethacin-treated goats

Repeated intramuscular injection of 1 mg prostaglandin F2 alpha (PGF2 alpha) during the luteal phase of the oestrous cycle of the goat hastened luteolysis and resulted in rapid increases in jugular concentrations of 13,14-dihydro-15-keto PGF2 alpha (PGFM), the primary metabolite of PGF2 alpha, and of oxytocin; similar injections of PGF2 alpha in indomethacin-treated goats had a reduced effect on PGFM and oxytocin concentrations, and failed to induce luteolysis. The same injections of PGF2 alpha were without effect on PGFM and oxytocin concentrations in ovariectomised goats. The results suggest that exogenous PGF2 alpha, or endogenous PGF2 alpha released at luteolysis, may induce the release of ovarian oxytocin in the goat.     

Effects of prostaglandin F2 alpha on prolactin secretion in the fowl

The plasma concentration of prolactin in immature cockerels was increased between 10 and 40 min after the intravenous administration of prostaglandin (PG) F2 alpha (200 micrograms/kg body weight). Lower doses had no effect on plasma prolactin concentration. The addition of PGF2 alpha (10(-9) to 10(-6) M) to incubation media had no effect on the basal release of pituitary prolactin but reduced the release of prolactin from pituitary-hypothalamus co-incubations. The addition of noradrenaline (10(-7) M), serotonin (10(-7) M), acetylcholine (10(-6) M) or histamine (10(-6) M) to the co-incubation increased the hypothalamus-induced prolactin release, although these effects were not observed in the presence of 10(-7) M PGF2 alpha. The in vitro release of pituitary prolactin was increased by adding chicken hypothalamic extract in the presence or absence of PGF2 alpha. These results suggest a dual effect on PGF2 alpha of prolactin secretion in the fowl; its stimulation in vivo may result from a peripheral action.     

Effect of prostaglandin F2 alpha, phenylephrine and ergonovine on uterine contractions in the ewe

Two experiments were conducted to determine the effect of prostaglandin F2 alpha (PGF2 alpha), phenylephrine and ergonovine on uterine contractions. In the first experiment, ewes were bilaterally ovariectomized, and a strain gauge force transducer was sutured to the serosa of one uterine horn. Each ewe was treated sc with 2 micrograms of estradiol-17 beta daily to prevent regression of the uterus. Beginning at least 5 d after ovariectomy, four dose levels of PGF2 alpha, phenylephrine and methoxamine were given by im injection and ergonovine was given by im or iv injection. Phenylephrine, methoxamine and ergonovine are alpha-adrenoceptor agonists. Uterine activity was recorded by physiograph for 30 min before and 90 min after treatment. Tracing were analyzed for 20-min periods before treatment and 4 to 24 min and 50 to 70 min after treatment. In Exp. 2, transducers were attached to uteri of intact ewes at d 10 to 12 of an estrous cycle. During subsequent estrus, one or two dose levels of PGF2 alpha, phenylephrine and ergonovine were given by im injection and uterine activity recorded. In Exp. 1, PGF2 alpha and phenylephrine increased (P less than .05 or .01) the number of amplitude of contractions at both 4 to 24 and 50 to 70 min. Ergonovine given im increased the number of contractions. In intact estrous ewes, PGF2 alpha increased the number and amplitude of contractions at 4 to 24 min, phenylephrine increased the number and amplitude at both 4 to 24 and 50 to 70 min, and ergonovine increased the number slightly but significantly at 4 to 24 min.(ABSTRACT TRUNCATED AT 250 WORDS)     

Variation in conception rates following synchronization of estrus with melengestrol acetate and prostaglandin F2 alpha

Beef cows and heifers (n = 263) at three locations that were exhibiting estrous cycle either were fed .5 mg/d melengestrol acetate (MGA) for 7 d and administered prostaglandin F2 alpha (25 mg, i.m.) on the last day of MGA feeding or were untreated. State of the estrous cycle at the beginning of the experiment was determined based on estrous detection and (or) progesterone concentrations in pretreatment blood samples. Estrous was checked twice daily for 30 d posttreatment. Animals were artificially inseminated approximately 12 h after detection of estrus. A synchronized estrus (less than 7 d posttreatment) was detected in 72% of the treated animals. More animals in the treated group became pregnant during the first 7 d of breeding, but their conception rate was lower than that of animals in the control group (P less than .05). Conception rate (36%) was reduced among treated animals when MGA feeding began late (d 14 to 20) in the estrous cycle. Conversely, the conception rate (66%) of treated animals fed MGA beginning earlier in the cycle was not different from that of control animals (73%; treatment x stage of cycle; P less than .05).