Plasma concentrations of 13,14-dihydro-15-ketoprostaglandin F2 alpha in mares during uterine involution.

Twelve mares were allowed to foal naturally, after which they were monitored to study uterine involution. Starting on day 3 after parturition, the internal genital tract was examined per rectum manually and ultrasonographically every other day for changes in uterine characteristics and ovarian activity. By day 5, gravid and nongravid uterine horns were similar in size, and by day 7, uterine fluid was absent. On day 7 after parturition, endometrial biopsy samples were obtained for histologic evaluation, and uterine swab specimens were obtained for microbiologic culture. Uterine swab specimens from 10 of 12 mares had slight bacterial growth. The uteri of 8 of the 12 mares were histologically involuted by day 7. All mares ovulated 7 to 12 days after parturition. Concentrations of 13,14-dihydro-15-keto-PGF2 alpha (PGFM) were measured in jugular plasma samples obtained daily for 21 days after parturition. Concentrations of PGFM were low by the day after parturition, and there was no significant correlation between uterine involution and PGFM concentrations in these mares. All 12 mares were bred at the first estrus after parturition, and 9 became pregnant.     

15-ketodihydro-PGF2 alpha, progesterone and cortisol profiles in heifers after induction of parturition by injection of dexamethasone.

In order to study rapid changes in 15-ketodihydro-PGF2 alpha, cortisol and progesterone in the period preceding parturition in cattle, pre-term parturition was induced in 4 late pregnant heifers. Parturitions were induced by 2 intramuscular injections of 20 mg dexamethasone with a 24-h interval. The first injection was made on days 254, 258, 264 and 265 in gestation, respectively. Twenty-four h before the first injection an intravenous polyurethane cannula was inserted. Blood samples were collected at least every hour until 12 h after parturition and during the second stage of labour at least 6 times per hour. Plasma was analysed for 15-ketodihydro-PGF2 alpha and progesterone by radioimmunoassays, and for cortisol by an ELISA. The average time from injection to parturition was 7.7 (6.6-8.9) days (mean (range)). Two of the heifers had retained foetal membranes (RFM). At the start of the experiment the levels of PGF2 alpha metabolite were low (< 300 pmol/L) and increased slowly to levels between 1000 and 2000 pmol/L at one day before parturition. During the last day, however, the levels increased rapidly and the highest levels (> 10,000 pmol/L) were reached at the time of delivery. No pulsatile release was seen. Immediately after foetal expulsion the PG-metabolite levels decreased rapidly in all animals. In the 2 animals with RFM, however, this decline ceased within a few h. The PG-metabolite levels in these animals then started to increase and reached levels as high as during parturition. Luteolysis occurred between 1.6 and 0.4 days before parturition in all animals. The cortisol profile showed a distinct peak at the time of parturition in the RFM heifers. This peak was absent in the non-RFM heifers. This study shows that the PGF2 alpha release at prepartal luteolysis and parturition is not pulsatile in cattle and that cortisol profiles in heifers with retained foetal membranes might differ from the profiles in non-RFM heifers at the time of parturition.     

Follicle stimulating hormone, luteinising hormone and progesterone concentrations in the blood of thoroughbred mares exhibiting single and twin ovulations

The concentrations of follicle stimulating hormone, luteinising hormone and progesterone were measured in serial blood samples taken throughout one or more oestrous cycles from 12 Thoroughbred mares, some of which exhibited single and others twin ovulations. The resulting profiles clearly demonstrated that no simple relationship exists between circulating gonadotrophin levels and subsequent ovulation rate in the mare. However, plasma progesterone concentrations during dioestrus are, as expected, higher following twin than single ovulations. The findings suggest that the underlying cause of twin ovulation in some mares may exist at the ovarian end of the pituitary-ovarian axis which controls follicular development and ovulation.     

Plasma progesterone in mares showing oestrus during early pregnancy (author's transl)]

Sixtyfour mares were examined 3 and 6 weeks after mating. Progesterone was measured in 22 mares 3 weeks after mating in order to see if this could be of any help in the oestrous diagnosis. None of the pregnant mares had plasma progesterone below 2 ng/ml. Pregnant mares that did not show oestrus had higher levels of plasma progesterone than pregnant mares showing signs of oestrus 3 weeks after mating. Clinical findings in pregnant and nonpregnant mares 3 weeks after mating is compared, and oestrus in pregnant mares is discussed.     

Plasma potassium and lactate concentrations in thoroughbred horses during exercise of varying intensity.

To investigate the effect of moderate to high intensity exercise of up to 6 min duration on plasma potassium and lactate concentrations, 6 Thoroughbred horses were studied using a treadmill at a 5 degree incline. Each test consisted of an 8-min standardised warm-up followed by an exercise bout at 8, 9, 10 or 12 m/sec. The horses were galloped at each speed for up to a maximum of 6 min or until signs of fatigue were present. The horses were then walked at 0 degree incline. Carotid arterial blood samples were taken during and after the exercise. At 8, 9 and 10 m/sec there was a general pattern of an initial rise in potassium to a peak around 1.5 min of exercise with the concentration then slowly decreasing. At 12 m/sec there was a continuous rise to a peak at the end of exercise in all horses. Immediately after exercise there was a rapid return (within 3-4 min) to the potassium concentrations recorded at the end of the warm-up period. Plasma lactate peaked around the end of exercise at all speeds. At the highest intensity of exercise the mechanisms for the re-uptake of potassium did not appear to be able to match the rate of efflux. In contrast, at less intense work loads, the rate of re-uptake appeared to be similar to or slightly greater than the rate of efflux. It is possible that a disturbance in this balance between efflux and re-uptake could result in a disturbance in normal neuromuscular function during exercise.     

The effect on pregnancy rate of progesterone administration after manual reduction of twin embryos in dairy cattle

Twin pregnancies are undesirable in dairy cattle as they increase the risk of abortion and have many negative effects on the profitability of the herd. The purpose of this study was to evaluate manual reduction of a twin embryo in dairy cows bearing unilateral twins. On day 34 of gestation, 33 cows were assigned to one of three treatment groups (n = 11 for each group): untreated cows (group control), amnion rupture (group AR), and amnion rupture plus treatment (intravaginal progesterone for 28 days) (group ART). A significantly higher (P = 0.0001) pregnancy loss rate was recorded in the AR group (100%, 11/11), than in the ART (54.5%, 6/11) and control (27.3%, 3/11) groups. In the ART group, one embryo survived amnion rupture and the cow bearing it had twins at parturition, while the remaining four cows delivered singletons. Our results suggest that the procedure of rupturing the amnion with progesterone supplementation may provide a satisfactory way for twin reduction in dairy cattle.     

Changes of plasma concentrations of steroid hormones, prostaglandin F2 alpha-metabolite and pregnant mare serum gonadotropin during pregnancy in thoroughbred mares.

Plasma concentrations of estrogens, gestagens, cortisol (F), 13, 14-dihydro, 15-keto PGF2 alpha (PGFM) and pregnant mare serum gonadotropin (PMSG) in 10 Thoroughbred mares were measured for a 11-month pregnancy period. Estrone (E1) and estradiol-17 beta (E2) levels gradually increased as the pregnancy advanced, showing a peak around Month 8 and decreased thereafter. Progesterone (P) levels increased on Months 3 and 11, and 17 alpha-OH-progesterone (17 alpha-OHP) levels peaked on Month 3, whereas 20 alpha-OH-progesterone (20 alpha-OHP) levels increased sharply after Month 6. PGFM indicated peaks on Months 2 and 11. F and PMSG levels peaked on Months 2 and 3. From factor analysis, Month, E1, E2 and 20 alpha-OHP were discriminated as Factor 1, increasing with the progress of pregnancy, PMSG, 17 alpha-OHP and P as Factor 2, showing a relation with the secondary corpus luteum, and PGFM and F as Factor 3, affecting PGFM change on Month 2 by F. P also related to both Factors 1 and 3, showing an inverse relation against PGFM. In conclusion E1, E2 and 20 alpha-OHP contained in Factor 1 were suggested to be important especially as parameters of placental function after Month 6.     

Intrafollicular and systemic serotonin,oestradiol and progesterone concentrations in cycling mares

The hypothesis that a local serotonergic network might also exist in the follicle of mares remains poorly documented, with exception for humans and laboratory species. For this reason, the aim of the present study was to clarify this possibility, investigating intrafollicular serotonin concentrations of the cycling mare at ovulation time. Sixty ovaries collected from 30 clinically healthy mares of slaughterhouse meat production with clinically normal reproductive tracts after slaughtering were evaluated. Blood samples were taken prior to sacrifice. Follicles were classified in three categories in relation to size, as small (20–30 mm), medium (31–40 mm) and large (>41 mm), and the follicular fluid samples were extracted from each follicle. Intrafollicular and systemic serotonin (5‐HT), oestradiol‐17β (E₂) and progesterone (P₄) were determined by means of enzyme‐linked immunosorbent assay and RIA, respectively. Intrafollicular 5‐HT, E₂ and P₄ concentrations were higher than systemic ones (p < .05). 5‐HT concentrations increased in larger compared to medium follicles, without differences compared to small size follicles (p < .05). 5‐HT and E₂ (r = .79) and 5‐HT and P₄ (r = .79; p < .05) were positively correlated. 5‐HT and P₄ concentrations in follicular fluid increased progressively with the increase in follicular size (p < .05). Follicle diameter and E₂ (r = .85) and P₄ (r = .68) were correlated (p < .05). Since serotonin interacts with steroids, its role on steroidogenesis during growth of the dominant follicle may be suggested.     

Pregnancy diagnosis in thoroughbred mares using radioimmunoassay (RIA), enzyme immunoassay (kit) and ultrasound echography (scanning)

On the basis of progesterone determination on plasma or blood after RIA and the kit method respectively and consecutive scanning performed on a total number of 31 mares the following features were demonstrated: The overall material shows that in 20 mares (64.5%) embryonic vesicles were demonstrated. Of these mares 16 have conceived after service in the 1st estrous cycle and 3 mares in the 2nd estrous cycle. 18 mares were scanned in the time interval 13th-26th day after the latest service, while 2 mares were scanned on day 46 and 41 respectively. A total of 14 scanning positive mares were examined for progesterone by the RIA as well as by the kit method. For these mares (100%) agreement was found between the progesterone analyses as well as with the scanning results. For 19 mares (100%) there was agreement between kit and scanning results. 15 RIA progesterone determinations are in agreement with the scanning results. Progesterone values after the RIA method performed on 15 scanning positive mares were in average 8.40 +/- 2.79 ng/ml plasma. A total of 9 out of 10 scanning negative mares have been examined by the RIA as well as by the kit method. In 6 of these mares with 7 estrous cycles agreement has been found between progesterone analyses and the scanning results (77.8%). In 2 mares (no. 2 and 4) discrepancy has been found in the 2nd estrous cycle between RIA, kit and scanning results. For 1 mare (no. 7) discrepancy has been found in the 1st and 3rd estrous cycle between RIA and scanning.(ABSTRACT TRUNCATED AT 250 WORDS)     

Changes in plasma progesterone concentrations in mares treated with cloprostenol and human chorionic gonadotropin and inseminated during estrus

Daily changes in the plasma progesterone concentrations were determined in eight mares treated with intramuscular injections of 250 μg cloprostenol, a prostaglandin analogue, followed five days later by 2500 I.U. human chorionic gonadotropin. A second cloprostenol injection was given 14 days after the first; the mares were then inseminated on the third and fifth day of the subsequent estrus and a second injection of human chorionic gonadotropin was administered on the fifth day. The onset of estrus following the second cloprostenol treatment was synchronized beginning three to four days after treatment in all eight mares. All eight ovulated, five mares conceived and only four foaled. Evaluation of the progesterone profiles provided reliable indicators of luteolysis, ovulation and luteal function. Decreasing plasma progesterone concentrations were associated with cloprostenol induced luteolysis or preceded spontaneous onset of estrus. The plasma progesterone concentrations increased consistently after ovulation, and in the pregnant mares, the progesterone concentrations remained high during the first month after insemination.     

Plasma progesterone concentrations in pregnant and non-pregnant llamas (Lama glama)

Female llamas ovulate in response to copulation, and progesterone secretion by the corpus luteum indicates recent ovulation (mating) and, or, pregnancy. The plasma progesterone concentration was 0.9 to 1.4 ng/ml in five non-pregnant llamas and 7.4 to 9.2 ng/ml in three llamas in the last month of pregnancy. After ovulation had been induced in nine of 10 llamas by a single intramuscular injection of 500 or 750 iu of human chorionic gonadotrophin, the plasma progesterone concentration increased after two days from 0.5 to 1.2 ng/ml to 4.6 to 10.3 ng/ml after six to nine days and returned to basal values after 10 to 13 days, reflecting the life-span of a corpus luteum in the absence of conception. After a male llama had been introduced into a group of 13 females, 10 matings which resulted in eight conceptions occurred in the first 11 days, and 11 of the llamas became pregnant. The llamas' progesterone concentrations increased after mating and remained high if conception had occurred: 6 to 12 ng/ml in months one to four, and 5 to 9 ng/ml in months five to nine of the 11-month gestation. Two of the 13 llamas had high concentrations of progesterone although they did not become pregnant.     

Plasma levels of cortisol, progesterone, oestradiol-17 beta and prostaglandin F2 alpha metabolite after ACTH (Synacthen Depot) administration in ovariectomized gilts

In order to elucidate the effect of stress on reproductive hormones, the present study was designed to investigate the effect of adrenocorticotropic hormone (ACTH) on the plasma levels of cortisol, progesterone, oestradiol-17 beta and prostaglandin F2 alpha metabolite in ovariectomized gilts. Ovariectomy and cannulation of the jugular vein were performed within 1 week of oestrous detection, under general anaesthesia. Approximately 1 week after surgery, two gilts were each administered ACTH (Synacthen Depot) intravenously, at a dose of 0.01 mg/kg body weight, and one gilt was given saline solution (5 ml). The reverse was performed on the following day. The administration of ACTH was followed by a concomitant elevation of cortisol, progesterone and prostaglandin F2 alpha metabolite but not of oestradiol-17 beta. Peak cortisol, progesterone and prostaglandin F2 alpha metabolite levels were reached at 80 +/- 10.0, 80 +/- 10.0 and 46.6 +/- 13.3 min after ACTH administration and the durations of the peaks were 181.8 +/- 19.8, 308.1 +/- 49.7 and 181.8 +/- 7.9 min, respectively. The total area under the curve for cortisol, progesterone and prostaglandin F2 alpha metabolite was significantly higher in the ACTH than in the control group. The present results indicate that during stress, cortisol, progesterone and prostaglandin F2 alpha levels are elevated while the level of oestradiol-17 beta is less affected. It can be concluded that the administration of ACTH to ovariectomized gilts, results in the elevation of cortisol, progesterone and prostaglandin F2 alpha metabolite but not of oestradiol-17 beta.     

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.     

The nature of embryo reduction in mares with twin conceptuses: deprivation hypothesis

Ultrasonography was used to determine whether there is embryo reduction in mares with unilaterally fixed twins when a major portion of the vascularized area of the wall of one of the embryonic vesicles is in apposition with the wall of the adjacent vesicle, rather than with the endometrium (deprivation hypothesis). In addition, the effect of ovulatory pattern (synchronous and asynchronous) on the incidence of embryo reduction was studied. Twin vesicles were ultrasonically detected on days 11 to 15 (ovulation = day 0) and were examined daily until there was embryo reduction or until day 40. In 31 mares with twin embryonic vesicles, unilateral fixation (71%) was more frequent (P less than 0.05) than was bilateral fixation (29%). In 28 mares with known ovulatory patterns, synchronous ovulations did not affect the type of fixation (9/17 unilateral and 8/17 bilateral); however, for asynchronous ovulators the frequency of unilateral fixation (10/11) was greater (P less than 0.01) than the frequency of bilateral fixation (1/11). The incidence of embryo reduction was greater (P less than 0.01) for unilateral fixation (14/19) than for bilateral fixation (0/9) and was greater (P less than 0.05) for asynchronous ovulators (9/11) than for synchronous ovulators (5/17). In mares with embryo reduction, the reduction was complete before detection of both embryo propers (early reduction) in 10/14 and after detection of both embryo propers (late reduction) in 4/14.(ABSTRACT TRUNCATED AT 250 WORDS)     

Plasma concentrations of sodium benzylpenicillin after intrauterine infusion in pony mares

Plasma concentrations of sodium benzylpenicillin were measured following intrauterine infusion at a dose rate of 22,000 u/kg (250,000 u/ml). The reproductive status of the mare at the time of infusion did not appear to influence plasma concentrations of penicillin, but preswabbing the endometrium for bacteriological culture resulted in peak plasma concentrations which were nearly twice those found in unswabbed mares.     

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)     

Plasma prolactin concentrations in mares and their neonates after oxytocin induction of parturition

Studies were undertaken to investigate the effects of oxytocin induction on prolactin release in term (Group II) and preterm (Group III) mares and to compare these effects to spontaneously foaling mares (Group I). Since physiological concentrations of prolactin in blood have not been measured in the neonatal foal, experiments were designed to monitor prolactin in the cord artery and jugular blood of the foals from all groups of mares. Although prolactin levels varied in term mares (Group I and II) during the last 11 days of pregnancy, an increase was observed between Day -6 and Day 0 (2.7 and 11.9 ng/ml respectively; P less than 0.1). The average concentration of prolactin over the last 4 days (Days -3 to 0) had increased by 40% when compared to the average concentration on Days -6, -5, and -4. These findings indicate a rising trend which appears to occur concomitantly with changes in concentrations of 2 mammary components tested, sodium and potassium. Prolactin concentrations did not significantly increase in term mares after oxytocin treatment or in spontaneously foaling mares. However, the preterm induced mares had higher prolactin concentrations during the first stage of labor (19.3 +/- 7.2 ng/ml) than prior to treatment with oxytocin (4.7 +/- 2.0 ng/ml; P less than 0.01). Levels of prolactin in all groups significantly declined by 20-min post-placental expulsion. For the first 30 min after birth, prolactin concentrations in foals from oxytocin-induced mares appeared to be 2-fold higher than those from spontaneously foaling mares. Thereafter, prolactin values declined to baseline values by 48 hrs. When comparing cord arterial plasma with cord venous plasma in each group, prolactin concentrations were similar. However, the average prolactin levels in both the cord artery and vein appeared higher (ave: 1.1 ng/ml) in Group II and III than in Group I (less than 0.5 ng/ml). From these results, the authors suggest that 1) prolactin may have a role in regulating mammary secretory products in mares just prior to parturition; 2) oxytocin may increase prolactin secretion in preterm induced mares; 3) oxytocin induction may have a short term effect to increase circulatory prolactin concentrations in neonates in utero regardless whether their dams were treated preterm or term.     

Plasma levels of prostaglandin F2 alpha metabolite and progesterone in repeat breeder heifers.

A detailed clinical-endocrine investigation was performed in 6 repeat breeder heifers (RBH) with the aim being to ascertain whether endocrine asynchronism exists at luteal regression and during early pregnancy. The heifers were first studied during an open cycle and then after insemination when 3 heifers became pregnant. Circulating plasma levels of PGF2 alpha metabolite were measured every 2nd h, while progesterone (P4) levels were measured every 6th h. The oestrous period and intervals between the onset of oestrus and ovulation were relatively longer, compared with what is normally seen in heifers. Plasma levels of P4 at the onset of oestrus were higher than normal, but it was concluded that the plasma levels of PGF2 alpha metabolite and P4 in RBH at luteal regression and early pregnancy were normal.