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Topic:Progesterone
Progesterone is a steroid hormone produced primarily by the ovaries in mares and plays a significant role in the reproductive system of horses. It is involved in the regulation of the estrous cycle and the maintenance of pregnancy. Progesterone levels fluctuate throughout the reproductive cycle, influencing reproductive behavior and physiology. In veterinary medicine, measuring progesterone levels can aid in diagnosing reproductive conditions and managing breeding programs. This page compiles peer-reviewed research studies and scholarly articles that explore the production, regulation, and clinical applications of progesterone in equine reproductive health.
Effects of injected ovarian steroids on reproductive patterns and performance in post-partum mares. Treatment of foaling mares with 150 mg progesterone and 10 mg oestradiol daily beginning within 12 h of parturition resulted in a delay of ovulation (15.6 +/- 2.6 days compared with 10.3 +/- 2.4 days in untreated mares). When mares were mated after this 5.3-day delay there was no advantage in reproductive performance over that of mares mated according to a conventional management system. Gonadotrophin secretion was inhibited during treatment but the following secretory patterns were similar to those of normal oestrous periods.
Effects of exogenous steroids on serum FSH and LH, and on follicular development in cyclic mares. Cyclic mares were given daily i.m. injections of 150 mg progesterone (Group P, N = 4), 150 mg progesterone and 10 mg oestradiol-17 beta (Group PE, N = 3), 10 mg oestradiol-17 beta (Group E, N = 3) or cottonseed oil vehicle (Group C, N = 4), from the day after ovulation (Day 1) to Day 28. Blood samples were collected daily, and the ovaries were palpated every 1-2 days. Serum FSH and LH concentrations were measured in all samples, and means determined for 7 consecutive 4-day periods throughout treatment. Comparisons within each steroid treatment group between time periods and comparisons between...
Identification of stage-specific and hormonally induced polypeptides in the uterine protein secretions of the mare during the oestrous cycle and pregnancy. Uterine secretions were obtained on Days 4, 8, 12, 14, 16, 18 and 20 of the oestrous cycle and early pregnancy. Acid phosphatase activity was significantly affected by day of the cycle, reaching a maximum at days 12-14 during the luteal phase and then declining to almost undetectable levels, by Day 20. In pregnant animals, activity continued to increase beyond Day 14. Two-dimensional polyacrylamide gel electrophoresis showed that albumin was a major component. However, a number of unique proteins of non-serum origin appeared in mid-cycle but had disappeared by Day 20. One of these was a basic ...
Progesterone, prostaglandin F-2 alpha, PMSG and oestrone sulphate during early pregnancy in the mare. Blood samples from 4 mares during the late luteal phase, oestrus, early pregnancy and up to about 150 days of gestation were analysed for 15-keto-13,14-dihydroprostaglandin F-2 alpha (PGFM), progesterone, PMSG and oestrone sulphate by radioimmunoassays. During the late luteal phase, at the time of corpus luteum regression and decreasing progesterone levels, PGFM peaks were recorded. During early pregnancy (i.e. from mating and up to about Day 30) no such peaks were detected. After mating the progesterone levels increased and remained high throughout the observation period. During the oestrous ...
Changes in plasma progesterone levels during storage of heparinized whole blood from cow, horse, dog and pig. Progesterone concentrations in heparinized plasma harvested immediately after blood collection were compared with levels obtained after storage of the corresponding whole blood for 2 h, 4 h, 6 h, 1 day, 2 days and 5 days at room temperature and in a refrigerator. The blood was taken during the luteal phase from 4 dogs, 4 horses, 4 pigs and 8 cows. For 4 cows the storage time was extended to 9 and 20 days. No significant effect of whole blood storage time on plasma progesterone concentrations could be shown for dogs or pigs. For the horse a slight but significant decrease was demonstrated when ...
Studies on the composition and antibacterial activity of uterine fluid from mares. Forty uterine fluid samples were obtained during oestrus and dioestrus of successive cycles from 4 mares classified as resistant to bacterial infection of the uterus. The flushings were assayed for peroxidase activity and ability to influence phagocytosis by polymorphonuclear neutrophils. Uterine fluid volumes and protein concentrations and serum oestrogen values were similar during oestrus and dioestrus. Serum progesterone concentrations were depressed during oestrus. Equine neutrophils adherent to glass slides were exposed to a genital strain of Streptococcus zooepidemicus suspended in salin...
Pituitary and chorionic gonadotrophic control of ovarian function during early pregnancy in equids. Concentrations of FSH, LH, chorionic gonadotrophin (CG) and progesterone were measured during early pregnancy in mares and donkeys carrying normal intraspecies and transferred extraspecies conceptuses. A secondary rise in progesterone concentrations occurred in normal intraspecies horse and donkey pregnancy soon after the appearance of CG but FSH concentrations continued to fluctuate and were not influenced by CG production. In donkeys carrying transferred horse conceptuses FSH concentrations fell sharply and progesterone concentrations rose steeply, coincidental with the appearance of abnorma...
Effect of PGF-2 alpha on LH receptors in the equine corpus luteum. As quantified by Scatchard analysis, a 27 000 g crude luteal membrane fraction contained a single population of unoccupied LH receptors characterized by high affinity, ka = 0.647 +/- 0.158 X 10(11) M-1 and low binding capacity, Rt = 4.91 +/- 0.78 X 10(-11) M/mg membrane fraction. Acceptable hormonal specificity, reversibility, saturability, high affinity and tissue specificity indicated that the binding protein was a physiological receptor. To ensure that the methods used for Scatchard analysis were valid, hCG was characterized for specific activity and maximum bindability, non-specific bindin...
Control of the oestrous cycle in mares with altrenogest. The clinical effectiveness of the synthetic progestagen, altrenogest, was evaluated in field trials with 449 mares during the 1980 breeding season. An oral dose of 27 mg altrenogest was administered daily for 15 days. In the first trial treated mares were compared with controls, and in the second trial the effectiveness of treatment for prolonged or erratic spring oestrus was evaluated. Oestrus was suppressed in 94% of the treated mares in the first trial. The post-treatment response was related to the stage during the transition from winter anoestrus to the spring breeding season and degree o...
Control of ovulation in mares in the early breeding season with ovarian steroids and prostaglandin. Two trials were conducted to (1) determine the degree of control of ovulation achieved by treating mares in late winter with progesterone and oestradiol-17 beta combined after prior exposure to an artificially increased photoperiod, and (2) to examine the effectiveness of such a procedure incorporated into equine breeding farm management systems. Following a 15-day treatment of 150 mg progesterone and 10 mg oestradiol-17 beta daily with 10 mg PGF-2 alpha on the last day of steroid treatment, 27 of 31 mares ovulated on Days 8-14 after the last injection in one trial. Conception rate for mares m...
Seasonal and individual effects on ovarian and endocrine responses of mares to a synchronization treatment with progestagen-impregnated vaginal sponges. The 8 saddle-type mares were treated with progestagen-impregnated vaginal sponges for 8 days and prostaglandin on the day of sponge removal. The treatment was given at random days of the cycle in April, May, July and September. Sponge insertion induced a sharp decrease in LH levels; at sponge removal, there was an immediate increase in LH and a large FSH rebound. Ovulation was synchronized 11 +/- 2 . 8 days (s.d.) after the end of treatment. In April the interval from sponge removal to ovulation was longer (14 days compared with 10 . 1, 10 . 7 and 10 . 2 days), the basal and peak LH levels low...
Concentrations of progesterone, 17 alpha-hydroxyprogesterone and 20 alpha-dihydroprogesterone in the plasma of mares during pregnancy and at parturition. Plasma concentrations of progesterone and 17 alpha-hydroxyprogesterone were high in the 2nd and 3rd months of gestation, but 20 alpha-dihydroprogesterone increased from a level of 2 ng/ml, during the first 3 months, to 10-15 ng/ml during months 5-10, to reach 80-120 ng/ml during the last 30 days before foaling.
Luteolysis in mares after endometrial biopsy. The length of diestrus was not changed in 4 mares by taking endometrial biopsy specimens during estrus. In contrast, taking endometrial biopsy specimens on postovulation day 4 induced premature luteolysis and significantly (P less than 0.05) reduced the length of diestrus. A concurrent decrease in serum progesterone occurred to verify the premature luteolysis in these mares. Bacterial cultures of endometrial swab samples from these mares were negative for growth at the first estrus before and after the last biopsy procedures, indicating that luteolysis was induced by the biopsy procedure and w...
Oestrus and pregnancy diagnosis by milk progesterone assay in the mare. The milk progesterone profiles of four mares were followed daily for four to five weeks after foaling. Progesterone was determined by direct radioimmunoassay using iodinated progesterone as the labelled antigen. The milk progesterone concentration varied from 1 to 5 nmol/1 (0·3 to 1·6 μg/1) during the first 10 days after foaling. The first ovulation took place at about the tenth day. During the luteal phase milk progesterone levels rose dramatically, reaching a maximum level of 30 to 45 nmol/1 (9·4 to 14·2 μg/1) within five to 10 days, and then fell to low levels unless pregnancy followe...
Plasma progesterone levels in the mare during the oestrous cycle and pregnancy. Plasma progesterone was determined with the aid of a competitive protein-binding assay in mares during the oestrous cycle, early pregnancy (45--60 days) and later pregnancy (2--10 months). Progesterone levels were low during oestrus (less than 1 ng per ml) (3,18 nmol/l) and reached high levels (often in excess of 10 ng per ml) (31.8 nmol/l) within 3--4 days after ovulation. The high luteal levels were maintained for approximately 5--8 days and then declined sharply over a period of approximately 24--48 hours to reach low levels at the subsequent oestrus period. In mares conceiving after servic...
Comparison of milk and blood plasma progesterone concentrations in cycling and pregnant mares. Progesterone concentrations were measured in milk and blood plasma for 15 mares throughout a normal estrous cycle and early pregnancy to determine the feasibility of utilizing progesterone in milk as an indicator of pregnancy. Samples were obtained daily from foaling until diagnosis of pregnancy by rectal examination at 30 to 35 days of gestation. Progesterone in milk and blood plasma was quantified by radioimmunoassay. Mean progesterone concentrations (+/- SE) in plasma from foaling to foal heat and during estrus, luteal phase and pregnancy were .51 +/- .09 ng/ml, .53 +/- .08 ng/ml, 3.88 +/- ...
Preliminary studies on the use of an oral progestogen to induce oestrus and ovulation in seasonally anoestrous Thoroughbred mares. Daily oral administration of 30 mg allyl trenbolone (Regumate) for 10 to 15 days to 61 barren, maiden and lactating Thoroughbred mares which were exhibiting either deep anoestrus, shallow anoestrus, prolonged spring oestrus or lactation anoestrus, resulted in 54 mares (88 per cent) showing oestrous behaviour within 8 days, and 51 mares (84 per cent) ovulating within 18 days, after the last dose of compound. Response rate was lowest in mares in deep anoestrus. Of the 38 Regumate-treated mares which were covered during the induced oestrus, 21 (55 per cent) conceived. The practical value of this ...
Induction of abortion in mares with equimate: effect on secretion of progesterone, PMSG and reproductive performance. Thirty-two light-horse mares were confirmed to be pregnant and assigned to one of four treatments: (1) injected with 250 micrograms of Equimate on day 70 and again on day 77 if abortion had not occurred; (2) injected with 250 micrograms of Equimate on day 70 and every 24 hr until abortion occurred (maximum four injections); (3) injected with 250 micrograms of Equimate on day 70 and every 12 hr until abortion (maximum eight injections); and (4) injected with 250 micrograms of Equimate once only on day 35 of gestation. Mares were observed four times daily for incidence of abortion or side effect...
[Diagnosis of early pregnancy by testing the progesterone level]. Measuring serum or plasma levels of progesterone can be used to determine if conception has occurred in horses. If the mare's progesterone level is below 2 ng/ml 18 days after mating has occurred, conception has not taken place. This method can be used as an addunct to genital examination, and it can be used to determine if hormonal irregularities are present in mares who have not been able to conceive.
Metabolism of progesterone by placentas from several mammalian species in vitro. 20-alpha-Hydroxysteroid oxidoreductase (20-alpha-HSDH) activity and 20-alpha-dihydroprogesterone concentration (20-alpha-DHP) reach peak values in the human placenta after vaginal delivery. To determine if these findings are unique to the human, we measured 20-alpha-HSDH activity as well as endogenous progesterone (P) and 20-alpha-DHP concentration in the soluble supernatant fraction of placental tissues obtained from rodents (rat, rabbit, guinea pig), ungulates (horse, zebra, giraffe, cow), and primates (squirrel monkey, orangutan, man). P concentration was very low in rodents (mean 0.60 ng/m...
Effects of restrictive suckling on postpartum reproductive performance in mares. Quarter Horse mares (n = 30) and their foals were used in a 2-year study. Objectives of the study were (i) to determine the effects of a treatment regimen, which permitted nursing for four 1-hour periods each day, on the postpartum reproductive performance of the dams, and (ii) to assess the effects of this procedure on the growth and development of foals. Mares in the restricted suckling treatment group showed estrus and ovulated sooner (P less than 0.01) after parturition than did control mares during the first year of the study, but not during the second year. Plasma progesterone concentrat...
In-vivo myometrial electrical activity in the cyclic mare. Uterine electromyography was performed by means of chronically implanted surface electrodes in 3 Pony mares during spontaneous oestrous cycles and following luteolysis induced by a prostaglandin analogue (fluprostenol). Three distinct patterns were recognized during the oestrous cycle. (1) During oestrus well defined phases of activity with closely grouped high-amplitude spikes were separated by long periods (10-45 min) of complete inactivity. (2) During dioestrus more diffuse phases of activity with low-amplitude spikes were separated by variable periods of relative inactivity. (3) During lut...
Effect of intrauterine saline infusion during the late luteal phase on the estrous cycle and luteal function of the mare. The intrauterine infusion of 500 ml of warm sterile saline solution into mares on days 12, 13, or 14 after ovulation failed to alter the ovulatory interval, although intervals were shorter for days 12 and 13 (20.6 days) when compared with those in control mares (21.6 days). The IU fusion shortened luteal-life-span on days 12 (12.0 vs 13.8 days) and 13 (13.0 vs 14.4 days) (P is less than 0.05), but not day 14 (14.0 vs 13.5 days), when comparing the effects of IU infusion with an average of before and after base-line data. There was no effect on the interval from corpus luteum regression to ovul...
