Clinical, hormonal and ultrasonograph approaches to diagnosing cryptorchidism in horses

Cryptorchidism is a partial or total failure of testicular descent. For a proper diagnosis different methods are required. The main aim of this study was to compare different diagnostic methods. Sixty two horses (15 stallions, 32 cryptorchids and 15 geldings) were used in the experiment. They were clinically examined and ultrasonography was used to locate the testes. Blood samples were taken from the animals to measure the plasma level of testosterone and total estrogen (RIA method). In 22 horses suspected of cryptorchidism, the hCG stimulation test was performed. Blood samples were taken every 20 minutes for 8 hours and then 24 and 48 hours after injection. Clinical examination had a 60% success rate in detecting superficial and profound canal cryptorchids. Inguinal ultrasonography had a 100% rate of detection when the retained testes were in the area of the internal or external inguinal ring. The rate of detection with abdominal cryptorchids was 72.7%. The highest levels of testosterone were found in stallions' blood (2.3 ng/ml), they were lower in cryptorchids (0.68 ng/ml) and lowest in geldings (0.15 ng/ml). Total estrogen levels revealed a similar tendency (respectively: 395 pg/ml, 228 pg/ml and 26 pg/ml). Administration of hCG usually increased the level of testosterone from 0.68 ng/ml to 1.05 ng/ml 60 minutes after injection. We found that to successfully diagnose cryptorchids in veterinary practice a combination of clinical, ultrasonographic and hormonal examinations should be used.     

Suppression of preovulatory luteinizing hormone surges in heifers after intrauterine infusions of Escherichia coli endotoxin

A study was conducted to test the hypothesis that high cortisol concentrations associated with products of infections (endotoxin) cause derangement in the neuroendocrine mechanism controlling ovulation in heifers. Eight Holstein heifers were given 2 injections of prostaglandin (PG), 11 days apart, to synchronize estrus. Starting from 25 hours after the second injection of PG (PG-2), the uterus of each heifer was infused with 5 ml of pyrogen-free water (control, n = 3) or Escherichia coli endotoxin (5 micrograms/kg of body weight) in 5 ml of pyrogen-free water (treated, n = 5), once every 6 hours for 10 treatments. Blood samples were obtained every 15 minutes via indwelling jugular catheter for an hour before and 2 hours after each infusion, then hourly until an hour before the next infusion. Ultrasonography of the ovaries was performed every 12 hours, starting 24 hours after PG-2 injection until 96 hours after PG-2 injection. Serum concentrations of luteinizing hormone and cortisol were determined by validated radioimmunoassays. Changes in cortisol concentrations were not detected in control heifers with preovulatory luteinizing hormone surges at 60 to 66 hours after PG-2 injection, followed by ovulations 72 to 96 hours after PG-2 was injected. None of the treated heifers ovulated, and the resulting follicular cysts (14 to 18 mm diameter) persisted for 7 to 21 days. In all treated heifers, serum cortisol concentrations increased (4- to 10-fold) during the first 2 hours after each infusion and then decreased gradually until the next infusion. Luteinizing hormone concentrations remained at baseline values throughout the treatment period in all treated heifers.(ABSTRACT TRUNCATED AT 250 WORDS)     

Diurnal variations in the plasma concentration of parathyroid hormone in dogs

The plasma concentrations of parathyroid hormone (PTH), ionised calcium (Ca(2+)), total calcium, albumin and inorganic phosphorus, and the pH were measured in blood samples obtained from nine dogs during a period of 26 hours. The plasma pth levels fluctuated slightly during the day, by about 20 pg/ml, but there was a distinct peak (42.8 [8.8] pg/ml) at 07.00. Plasma Ca(2+) showed a diurnal pattern in which two peaks (increases of 0.03 mmol/l) were observed at 05.00 and 17.00, and the plasma concentration of inorganic phosphorus showed a similar pattern. There were no diurnal changes in total calcium or albumin.     

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.     

Changes in the plasma concentration of immunoreactive arginine vasotocin during oviposition in the domestic fowl

1. The plasma concentrations of immunoreactive arginine vasotocin (AVT) were measured during oviposition and shortly before ovulation of the first egg (Cl) of a clutch. Immunoreactive AVT was determined on bentonite extracts of 0·5 ml plasma samples using the method of Rosenbloom and Fisher (1974). The R‐70 antiserum used to measure AVT cross reacted with arginine vasopressin (AVP), however the fowl pituitary does not synthesise AVP.

2. Over a period of 10 to 90 min before oviposition the plasma AVT concentration was about 20 pg/ml; during oviposition it increased four‐fold.

3. Measurements made at frequent intervals showed that plasma AVT concentration increased 5 to 6 min before oviposition, reached a peak during oviposition itself and decreased rapidly in the following 5 to 6 min.

4. The surge in plasma AVT occurred on average 48 min before Cl ovulation.

     

Serum immunoreactive gastrin activity in horses: Basal and postprandial values

Using commercially available diagnostic reagents, serum immunoreactive gastrin activity was measured in five normal horses that were starved of food and water for 24 hours. Blood samples were taken every 15 minutes for two hours. The horses were then fed a pelleted diet for 15 minutes and samples were taken every 15 minutes for a further two hours. Three further samples were taken at hourly intervals. The total sampling period was seven hours. Basal immunoreactive gastrin activity was lower than that reported in other mammals, ranging from a mean of 7.0 pg/ml to 13.8 pg/ml. At 30, 60 and 75 minutes after feeding, mean gastrin immunoreactivity was significantly elevated at 17.4, 19.8 and 18.2 pg/ml respectively. A late significant elevation occurred also five hours after feeding reading 19.4 pg/ml. This low activity may reflect a lower concentration of serum gastrin in the horse than in other mammals, or the methods used in the study may have failed to detect equine serum gastrins.Supported in part by a grant from the Board of the Veterinary Clinical Center, Michigan State University.     

Function of prostaglandins, thromboxane A2, and histamine in hypersensitivity reaction to experimental bluetongue disease in calves

Calves given 2 subcutaneous inoculations (4 ml, 4.5 weeks apart) of an inactivated bluetongue virus serotype 17 (BTV-17), aluminum hydroxide adjuvant, and cimetidine (600 mg) or levamisole (819 mg, 6 ml) combination were challenge exposed with virulent BTV-17 (2.5 x 10(5) embryo lethal dose) 9 weeks after the 1st inoculation and were monitored for 35 days. Plasma prostaglandins (PG) and thromboxane (Tx) B2 were measured by radioimmunoassay. Histamine was assayed spectrofluorometrically. During the inoculation period (9 weeks from the 1st inoculation to challenge exposure) PGE and histamine increased from base-line concentrations of 34 +/- 3 pg/ml and 1.2 +/- 0.1 ng/ml to 83 +/- 8 pg/ml and 2.0 +/- 0.1 ng/ml, respectively, whereas PGF2 alpha decreased from base-line values of 356 +/- 41 pg/ml to 226 +/- 16 pg/ml. Significant (P less than or equal to 0.05) changes from base-line TxB2 values (110 +/- 7 pg/ml) were not observed during the inoculation period. After challenge exposure, maximum increases were observed in TxB2 (157 +/- 10 pg/ml), PGF2 alpha (713 +/- 93 pg/ml), PGE (140 +/- 30 pg/ml), and histamine (3.6 +/- 0.2 ng/ml) concentrations at 4, 7, 7, and 14 days after challenge exposure, respectively. Concentrations of PGF2 alpha and TxB2 decreased from base-line values to 211 +/- 42 pg/ml and 75 +/- 11 pg/ml, respectively, 21 days after challenge exposure and then returned to base-line values. Significant changes were not observed in plasma concentrations of 6-keto-PGF1 alpha. Results indicate that PG, TxA2, and histamine may be involved in the hypersensitivity reaction to BTV in cattle.     

The relation between ultrasonographic observations in the oviduct and plasma progesterone, luteinizing hormone and estradiol during the egg laying cycle in ostriches

In this study we investigated the temporal relationship between ovulation, egg formation, oviposition and the changes in plasma concentrations of progesterone, luteinizing hormone and estradiol-17beta during the egg laying cycle in farmed ostriches. In 10 egg-producing birds, transcutaneous ultrasound scanning was performed at 3h intervals and blood sampling at hourly intervals during a period of at least 48h (one egg laying cycle). In hens (n=8) that ovulated during the observational period, the ovulated egg was first detected 2h after oviposition; thus, ovulation occurred shortly after oviposition in all birds. During the period between two consecutive ovipositions, the developing egg remained for 9h in the proximal part (infundibulum, magnum or isthmus) and for 39h in the distal part of the oviduct (uterus). In ovulating hens, plasma progesterone concentrations showed a characteristic and consistent profile: from basal levels of around 0.1ng/ml concentrations started to increase 12h before oviposition, reached an average maximum of 3.5ng/ml at 3h before oviposition and returned to basal levels 3h and 30min after oviposition. Changes in plasma luteinizing hormone and estradiol-17beta concentrations showed comparable patterns of elevation and decline relative to the timing of oviposition and ovulation. However, variation in their individual basal concentrations was generally larger and peak values were less conspicuous than those of progesterone. In non-ovulating hens (n=2) neither progesterone, nor luteinizing hormone nor estradiol-17beta showed elevations to peak concentrations before oviposition. These data demonstrate that during the egg laying cycle of ostriches, events such as ovulation, egg development and oviposition evolve according to a rather strict time schedule, and that progesterone, luteinizing hormone and estradiol-17beta reach peak concentrations shortly before ovulation. Additionally, our findings also show that on-farm ultrasound scanning is a useful technique to discriminate between ovulating and non-ovulating hens.     

Total estrogen concentrations in the blood plasma of calves during the first six days of life

From 47 mature calves ten blood samples were taken during the first six days of life for determination of total estrogen concentrations. Immediately postnatal concentration of total estrogens in blood plasma was high (1093.2 +/- 452.5 pg/ml blood plasma). Total estrogen values increased towards the sixth hour of life (1789.0 +/- 892.2 pg/ml blood plasma), which is thought to be caused by reabsorption of estrogens released from intracorporeal reservoirs. Towards the 48th hour of life total estrogen values decreased. This decrease indicates a progressive depletion of the reservoirs and also metabolisation and elimination of estrogens by the organism. The fact that total estrogens were nearly unchanged from the 4th day of life onwards reveals the approximative completed elimination of estrogens. At no time significant differences of total estrogen concentrations in blood plasma were found between female and male newborn calves.     

Catecholamine blood levels in sheep during superovulation in estrus]

The effects of a serum gonadotropin (SG) superovulation hormonal preparation were investigated on catecholamine levels (norepinephrine, dopamine and epinephrine) in the blood plasma of ewes with synchronized oestrus in the oestrus period. In this trial the blood plasma of eleven ewes of the Slovak Merino breed was analyzed to detect catecholamines in the oestrus period. Superovulation was induced by an i.m. administration of 1500 IU SG as soon as oestrus synchronization with Agelin vaginal tampons finished (20 mg chlorsuperlutin) which lasted for 10 days. Catecholamines were detected in the blood plasma before synchronization, on the day of Agelin vaginal tampons application, and in 48 and 72 hours after the hormone administration--on the days of the expected ovulation. Catecholamine concentrations in the blood plasma were determined by a radioenzymatic assay using a Catechola test (Praha). The results indicate that synchronization and hormonal stimulation influence plasma catecholamine levels. The norepinephrine (NE) concentration in the blood plasma of the control samples has the value of 8.31 +/- 0.732 pmol/ml. An insignificant increase in the NE levels (13.12 +/- 0.120 pmol/ml; Fig. 1) was recorded on day 1 of the trial, after the start of synchronization. On the day of the expected ovulation the NE concentrations rose to 17.12 +/- 1.289 pmol/ml (P less than 0.001) and they remained significantly increased (P less than 0.01) at the level of 12.89 +/- 1.020 pmol/ml on the following day of the experiment. The dopamine level (DA) in the plasma of a control sample is 6.42 +/- 0.350 pmol/ml (Fig. 2).(ABSTRACT TRUNCATED AT 250 WORDS)     

Role of prostaglandins in pathogenesis of bovine mastitis induced by Escherichia coli endotoxin

Four doses (5 to 100 micrograms, 1 dose/quarter) of Escherichia coli endotoxin were introduced into lactating mammary glands of 2 cows. There was no effect on milk prostaglandin (PG) E2 concentration, except that the concentration was increased from 200 pg/ml of milk to 1,060 pg/ml at post-treatment hour (PTH) 8 in cow 1 and from 75 to 420 pg/ml at PTH 4 in cow 2 after the highest dose 100 micrograms. Endotoxin caused a dose-dependent increase in milk PGF2 alpha concentrations in both cows. After the highest dose, PGF2 alpha was maximally increased from 200 to 3,500 pg/ml at PTH 4 in cow 1 and from 250 to 2,000 pg/ml in cow 2 at PTH 8. The instillation of 50 micrograms of endotoxin in all 8 quarters of 2 more lactating cows caused no significant (P greater than 0.05) changes in milk PGE2 and thromboxane B2 concentrations, whereas milk PGF2 alpha was significantly increased from the base-line value of 642 to 2,683, 1,189, and 2,281 pg/ml at PTH 4, 8, and 12, respectively. The 6-keto-PGF1 alpha was also significantly increased from the base-line value of 305 to 871, 631, and 600 pg/ml at the corresponding times, respectively. A marked increase in vascular permeability, as judged by high concentrations of serum albumin in the whey, was observed as early as PTH 4 and peaked at PTH 12 followed by a gradual decline, although it remained significantly increased over the control for 48 hours after treatment.(ABSTRACT TRUNCATED AT 250 WORDS)     

Validation of a radioimmunoassay for measurement of gastrin in equine serum

A commercial radioimmunoassay kit designed for measuring gastrin in human serum was validated for use with equine serum. This nonextraction, double-antibody procedure uses an antiserum with broad specificity for molecular forms of gastrin. Synthetic human gastrin (G17-I) was added to pooled equine serum, and the observed assay values were compared with the mass added. Recovery was 99 to 115% in the gastrin concentration range of 40 to 640 pg/ml. Dilutions of postprandial serum with serum from fasted horses were assayed, and the inhibition curves were compared with those of the human gastrin kit standards, using a log-logit transformation. The slopes of the sample dilution plots were not significantly different from the slopes of the standard curves. Ethylenediamine tetraacetate and heparin adversely affected the assay, resulting in lower assayed gastrin concentration values. The intra-assay coefficient of variation (n = 10) was 3.8%, and the interassay coefficient of variation (n = 6) was 11.2%. The assay sensitivity, as reported by the manufacturer, is 8 pg/ml. Gastrin concentrations in serum from fasted horses ranged from undetectable values (less than 8 pg/ml) to 17.5 pg/ml, and peaked at a mean value (n = 6) of 70 pg/ml 3 hours after feeding. Serum cortisol values monitored during the postprandial blood collection period were in the normal range for horses.     

Peri-oestrus hormone profiles and follicle growth in lactating sows with oestrus induced by intermittent suckling.

This study describes follicle dynamics, endocrine profiles in multiparous sows with lactational oestrus compared with conventionally weaned sows (C). Lactational oestrus was induced by Intermittent Suckling (IS) with separation of sows and piglets for either 12 consecutive hours per day (IS12, n = 14) or twice per day for 6 h per occasion (IS6, n = 13) from day 14 of lactation onwards. Control sows (n = 23) were weaned at day 21 of lactation. Pre-ovulatory follicles (> or =6 mm) were observed in 100% of IS12, 92% of IS6 and 26% of C sows before day 21 of lactation and in the remaining 74% C sows within 7 days after weaning. All sows with pre-ovulatory follicles showed oestrus, but not all sows showed ovulation. Four IS6 sows and one IS12 sow developed cystic follicles of which two IS6 sows partially ovulated. Follicle growth, ovulation rate and time of ovulation were similar. E(2) levels tended to be higher in IS sows (p = 0.06), the pre-ovulatory LH surge tended to be lower in IS12 (5.1 +/- 1.7 ng/ml) than in C sows (8.4 +/- 5.0 ng/ml; p = 0.08) and P(4) levels were lower in IS12 and IS6 than in C sows (at 75 h after ovulation: 8.8 +/- 2.4 ng/ml vs 7.0 +/- 1.4 ng/ml vs 17.1 +/- 4.4 ng/ml; p < 0.01). In conclusion, sows with lactational oestrus induced by IS are similar to weaned sows in the timing of oestrus, early follicle development and ovulation rates, but the pre-ovulatory LH surge and post-ovulatory P(4) increase are lower.     

Serum cortisol and progestin concentrations in pregnant and non-pregnant Asian elephants (Elephas maximus)

Blood samples were collected during the estrous cycle (n=3), throughout gestation (n=3), and during the periparturient period (n=11) to assess serum concentrations of cortisol in pregnant and non-pregnant Asian elephants whose reproductive status was being monitored by serum progestin determination. While serum cortisol concentrations remained constant throughout gestation, progestin concentrations decreased significantly (p<0.05) in the second half of pregnancy, declining to undetectable levels by 3 days before calving. During the non-luteal phase of the estrous cycle serum progestins varied from undetectable levels to 100pg/ml (53+/-10.7pg/ml) then increased steadily during the luteal phase (322+/-207.5pg/ml). There were no significant differences between serum cortisol concentrations during the luteal and those of the non-luteal phase (p>0.05). The mean cortisol concentration during the estrous cycle was about twice that during pregnancy (p>0.05). No substantial changes in maternal cortisol were found during the course of pregnancy or the periparturient period.     

Temporal changes in endogenous estrogens and expression of behaviors associated with estrus during the periovulaory period in Murrah buffaloes (<Emphasis Type="Italic">Bubalus bubalis</Emphasis>)

The objective of this study were (1) to establish the duration of behavioral estrus signs and timing of ovulation in Murrah buffaloes (n = 10) and (2) to determine relationship between behavioral estrus signs with change in plasma estrogen concentrations. Estrus and its behavioral signs were detected at hourly intervals by visual observations, per recta examination of genitalia and bull parading four times in a day for 30 minutes each. Among the behavioral signs of estrus, swollen vulva (80%) was the best indicator of estrus followed by excitement (70%). Among the duration of behavioral estrus signs the first and longest duration of estrus signs was swollen vulva which was seen upto 19.8 ± 0.8 h after onset of estrus. The mean total duration of estrus symptoms from appearance to disappearance of all the behavioral estrus symptoms was 23.5 ± 1.7 h. All the behavioral estrus symptoms were observed during the period of estrogen surge. Endocrine profile during the periestrus period showed that the mean peak concentrations of total estrogen 23.9 ± 3.9 pg/ml occurred at 8.8 ± 1.7 h after onset of estrus. The average number of estrus symptoms observed per animal during onset of spontaneous estrus was 5.7. Ovulation occurred after 37.4 ± 1.7 h after onset of estrus and 13.4 ± 1.0 h after end of total estrogen surge respectively. In conclusion, our results suggest that all signs of behavioral estrus occurred during the preovulatory rise in estrogens. The first sign of estrus to be observed was a swollen vulva and this symptom persisted the longest.     

Pharmacokinetics of oestriol after repeated oral administration to dogs

The aim of the present study was to investigate the pharmacokinetics of oestriol in plasma in the dog after repeated oral administration of oestriol tablets, a preparation intended for the treatment of urinary incontinence in the bitch. The study was performed in six healthy, entire, adult female beagle dogs. The bitches were treated once daily with two tablets, containing 1 mg oestriol per tablet, for seven consecutive days (days 1-7). Blood samples were taken from the jugular vein before treatment, frequently on days 1, 3 and 7 of the treatment period and daily just before (C(trough)) and 1 h after dosing (C(t=1h)). During the washout period samples were taken at a 24 h interval up to four days post-treatment. Oestriol concentrations were determined in plasma by radioimmunoassay. Pharmacokinetic parameters, AUC, C(max) and t(max), were determined from the plasma concentration-time curves using non-compartmental methods. The between animal variation in C(max) and the AUC was high. Individual values of the C(max) varied from 206 pg/ml (day 1) to 1128 pg/ml (day 7) and the AUC(0-24h) from 789 pg x h/ml (day 1) to 5718 pg x h/ml (day 7). t(max) occurred within 1 h. The mean C(trough) value was slightly above the pre-treatment level ( 38+/-2 pg/ml vs. 18+/-5 pg/ml). Within 48 h after the last treatment the concentrations had returned to the pre-treatment values. C(max) and C(trough) did not increase during the treatment period, indicating that no accumulation occurred. A shoulder in the concentration-time curve around 8-12 h after treatment strongly suggested the existence of enterohepatic recirculation (EHR). The average relative contribution of the EHR to the AUC(0-24h) was estimated to be 22%, 38% and 44% on days 1, 3 and 7, respectively. These mean values were calculated from five animals per time point, because one dog failed to show EHR on days 1 and 3 and was therefore excluded from the calculations.     

Plasma progesterone, oestradiol-17β and total oestrogen profiles in relation to oestrous behaviour during induced ovulation in Murrah buffalo heifers

The objectives of this study were to establish the characteristics of oestrous behaviour in Ovsynch (induction of ovulation through administration of GnRH-PGF2-GnRH in a systemic manner on 0, seventh and ninth day respectively) and Ovsynch plus Norprolac (Quinagolide hydrochloride – an inhibitor of prolactin secretion) treated Murrah buffalo heifers and to determine the relationships between this behaviour and the plasma concentrations of oestradiol-17β (E2), total oestrogen, and progesterone. Oestrus was detected by visual observations of oestrus signs, per rectal examination of genitalia and bull parading thrice a day during treatment period. Among all the symptoms, it was observed that bull mounting of heifers in oestrus was highest. Examination of genital tracts per rectum revealed that the cervix was relaxed, uterus was turgid and ovaries had palpable follicle in animals with oestrus. The peak concentrations of E2 (10.81 ± 0.62 pg/ml) and total oestrogen (17.11 ± 1.21 pg/ml) occurred at 9.45 ± 0.85 and 9.64 ± 0.93 h after second GnRH administration, respectively, in Ovsynch treated animals. However, the peak levels of E2 (20.02 ± 2.87 pg/ml) and total oestrogen (32.71 ± 3.15 pg/ml) occurred at 10.18 ± 0.50 and 10.36 ± 0.75 h after second GnRH administration, respectively, in Ovsynch plus Norprolac treated animals. Plasma progesterone concentration was basal (0.20 ± 0.001 ng/ml) during the peri-oestrus period. The plasma progesterone concentration was the lowest on the day of oestrus and increased to register a peak on day 13 ± 2 of the cycle. Oestrous behaviour was positively correlated with the peak concentration of E2 (p < 0.001) and total oestrogen (p < 0.001) during the peri-oestrus period. Inhibition of prolactin by Norprolac administration significantly increased the concentration of E2 and total oestrogen during oestrus in buffaloes in comparison to those recorded in animals subjected to Ovsynch protocol alone. In conclusion, our results suggest that the peak concentrations of E2 and total oestrogen and mean level of E2 and total oestrogen during the peri-oestrus period are the important factors contributing the behavioural manifestation of oestrus in buffalo cows.     

Endocrine patterns in the postpartum beef cow associated with weaning: a comparison of the short and subsequent normal cycles

Levels of luteinizing hormone (LH), follicle stimulating hormone (FSH), progesterone and estradiol-17 beta were measured in five Polled Hereford cows. Blood samples were collected once or twice daily for 5 d, then every 6 h from 1 d before weaning (d 28 to 38 postpartum) until 10 d after the second postweaning estrus. Blood samples were again collected at daily intervals until the third postweaning estrus. All cows exhibited estrus within 4 d after weaning, a second estrus 8 to 10 d after the first and a third estrus 16 to 23 d after the second. All cows had peaks in serum concentrations of LH during the first (22.6 to 81.7 ng/ml) and second (4.4 to 149.0 ng/ml) postweaning estrus. Mean levels of LH in serum during the peak and the area under the LH curve during the first and second postweaning estrus did not differ. Serum levels of LH and FSH during the first 4 d of the short cycle did not differ from LH and FSH levels the first 4 d of the subsequent normal cycle. Levels of LH in serum for 4 d before the first LH surge, associated with the first postweaning estrus, did not differ from levels of LH found 4 d before the second Lh surge, associated with the second postweaning estrus. However, serum levels of FSH during the 4 d before the first ovulatory LH surge were lower (P = .05) than those observed during the 4-d period before the second ovulatory surge of LH. Progesterone levels were similar the first 6 d after the first and second estrous periods, but were lower after d 6 of the first (short) cycle than after d 6 of the second (normal) cycle. Estradiol peaks of 1.2 to 2.8 pg/ml were detected during the first postweaning estrus and 1.4 to 12.5 pg/ml during the second postweaning estrus, but due to the variability among cows mean levels of estradiol during first estrus did not differ from second estrus. These data agree with previous reports that postpartum anestrous cows had short cycles if they exhibit estrus in response to weaning. The early decline of progesterone after the first estrus apparently did not stem from lack of LH in serum, but the lower levels of FSH observed before this first ovulation may have been an important factor contributing to the reduced life span of the subsequent corpus luteum.     

Postpartum Ovarian Activity and Serum Estradiol-17beta Level in Thai Crossbred Native Mares

To study the postpartum ovarian activities for investigation of first postpartum oestrus, twenty-five Thai crossbred native mares were monitored after parturition by oestrous detection, transrectal palpation and reproductive ultrasonography. Blood samplings were also taken for estradiol-17beta (E2) analysis. The first ovulation occurred within 20 days postpartum in 92% (23/25) of the mares. The mean intervals of foaling to first oestrus and to first ovulation were 10.3 +/- 2.9 and 13.4 +/- 2.6 days (mean +/- SD) respectively. Serum E2 increased from 7.0 +/- 2.9 to a peak of 10.8 +/- 3.3 pg/ml (mean +/- SD) at 2 days before ovulation. In conclusion, from the study, it can be stated that the postpartum breeding management should be considered after day 10 postpartum by careful examination of ovarian activity with various methods. However, the uterine condition should be also estimated associated with the ovarian activity after parturition which may increase breeding performance and foal production.     

Changes in plasma estrogen, luteinizing hormone, follicle-stimulating hormone and 13,14-dihydro-15-keto-prostaglandin F2 alpha during blockade of luteolysis in pigs after human chorionic gonadotropin treatment

An injection of human chorionic gonadotropin (HCG) or estrogen on d 12 of the estrous cycle delays luteolysis in the pig. In an experiment to determine if HCG stimulated estrogen secretion, 21 cyclic pigs received one of five different amounts of HCG-(A) 0, (B) 125, (C) 250, (D) 500 or (E) 1,000 IU-as a single, im injection in 2 ml of distilled water on d 12 of the estrous cycle. Blood was collected from the jugular vein immediately before HCG injection and once daily thereafter until d 20 of the estrous cycle. Plasma progesterone, estrogen (unconjugated) and 13,14-dihydro-15-keto-prostaglandin F2 alpha (PGFM) were quantified for pigs in all groups; luteinizing hormone (LH) and follicle-stimulating hormone (FSH) were quantified for pigs in groups A and E. The HCG injection exerted a dose-related increase on the mean interestrus interval (groups A, B, C, D and E were 20.5, 20.2, 22.5, 31.0 and 61.4 d, respectively) and on the delay of luteolysis as measured by mean plasma progesterone on d 16 (A, B and C vs D and E, respectively, 1.9, 1.2 and 10.4 vs 34.1 and 47.1 ng/ml; P less than .05). The HCG injection caused a transitory increase in plasma estrogen from d 12 (5 to 10 pg/ml before treatment) to d 15 (35.5 pg/ml, group D) and to d 16 (90.2 pg/ml, group E) before it decreased to preinjection levels on d 17 (group D) and 18 (group E).(ABSTRACT TRUNCATED AT 250 WORDS)