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1.
Reasons for performing study: Active immunisation against gonadotrophin‐releasing hormone (GnRH) provides a reversible method for control of oestrous behaviour and fertility in mares. Previous reports failed to demonstrate the interval to resumption of cyclic ovarian activity after GnRH‐vaccination. Hypothesis: Administration of the GnRH‐vaccine Improvac in a large group of mares of various ages will result in effective, reliably reversible suppression of ovarian activity within a 2 year period. Methods: The mares, subdivided into 3 age categories, were vaccinated twice (with a 35 day interval) using 400 µg Improvac and monitored via blood samples until Day 720 after initial vaccination for serum progesterone concentration determination by radioimmune assay and anti‐GnRH antibody titre by enzyme immunoassay. Samples were collected until individuals resumed cyclic ovarian activity. Results: All mares showed suppression of cyclic ovarian activity by clinical examination and serum progesterone concentration (SPC) ≤1 nmol/l by Day 70 and 92.2% resumed cyclic activity by SPC at Day 720 with a mean interval = 417.8 days (s.d. ± 23.9; range 232–488 days, median 344 days). A significant age effect (P = 0.028) on the interval, but not on GnRH‐antibody titre response, was observed between the youngest (≤4 years) and oldest (≥11 years) categories. Conclusions: Immunising adult mares of all ages with Improvac resulted in a reversible suppression of cyclic ovarian activity in most mares. An age effect, with the youngest mares showing a longer interval to reversibility, was observed.  相似文献   

2.
Two experiments were conducted to determine the effect of exogenous gonadotropins on follicular development in gilts actively immunized against gonadotropin releasing hormone (GnRH). Four gilts, which had become acyclic after immunization against GnRH, and four control gilts were given 1,000 IU pregnant mare serum gonadotropin (PMSG), while four additional control gilts were given saline. Control animals were prepuberal crossbred gilts averaging 100 kg body weight. Control gilts given saline had ovaries containing antral follicles (4 to 6 mm in diameter). Control gilts given PMSG exhibited estrus and their ovaries contained corpora hemorrhagica and corpora lutea. PMSG failed to stimulate follicular growth in gilts immunized against GnRH, and ovaries contained regressed corpora albicantia and small antral follicles (less than 1 mm in diameter). Concentrations of luteinizing hormone (LH) and estradiol-17 beta (E2) were non-detectable in gilts immunized against GnRH and given PMSG. In the second experiment, five gilts actively immunized against GnRH were given increasing doses of PMSG every third day until unilateral ovariectomy on d 50. PMSG failed to stimulate follicular growth, and concentrations of follicle stimulating hormone (FSH), E2 and LH were not detectable. Six weeks later, gilts were given a booster immunization and then were given 112 micrograms LH and 15 micrograms FSH intravenously every 6 h for 9 d. The remaining ovary was removed on d 10. Although LH and FSH concentrations were elevated, administration of gonadotropins did not stimulate follicular growth or increase E2 concentrations. These results indicate that neither PMSG or exogenous LH and FSH can induce E2 synthesis or sustain follicular development in gilts actively immunized against GnRH.  相似文献   

3.
The effects of exogenous equine somatotropin (eST) administration on ovarian activity and plasma hormone levels were evaluated on horse and pony mares. The objectives of this study were to determine the effects of eST on follicular development and circulating concentrations of leutinizing hormone (LH), estradiol, progesterone, and insulin-like growth factor I (IGF-I) in cyclic horse and pony mares. Sixteen mares received daily injections (i.m.) of eST at a concentration of 25 micrograms/kg body weight on either Days 6 through 12 (Treatment A) or 13 through 19 (Treatment B) postovulation. In addition, contemporary mares were similarly given the carrier vehicle and served as controls (Treatments C and D). Blood samples were collected at 24-hr intervals and ultrasonographic evaluations were performed on the ovaries of each mare at 48-hr intervals beginning on the first day of treatment and ending either on the day of ovulation or 5 d postovulation. Circulating levels of insulin-like growth factor-I (IGF-I) were increased in treated mares by Day 3 post-treatment (P < 0.05). Also, mares in Treatment B exhibited a decrease in plasma estradiol concentrations (P < 0.05) when compared with control mares on Days 1 through 5 postovulation of the post-treated estrous cycle. In addition, circulating leutinizing hormone levels were different for mares in Treatment A compared with controls on Days--8 through--1 pre-ovulation (P < 0.05). All follicles present on the ovaries of each mare were measured and placed into one of five categories based on their diameter. Neither the mean number of follicles per size category > or = 8 mm in diameter nor the mean follicular diameter within each size category differed among treatment and control mares. However, eST treatment significantly increased the number of follicles < or = 7 mm on the ovaries of mares treated early in the estrous cycle when compared with control mares on Days 3 and 7 post-treatment and at the onset of standing estrus.  相似文献   

4.
Two pony mares were immunized against recombinant porcine inhibin alpha subunit three times with 39 day intervals. Clinical findings and endocrinological changes before immunization were taken as the control. The first significant rise in the anti-inhibin titre (P<0.05) in the circulation was found 27 days after the first injection. Maximum binding activity was reached by the 12th day after the second booster dose. The number of small, medium and large sized follicles had increased significantly compared to before immunization (11.75 +/- 4.30, 2.75 +/- 0.69 and 2.51 +/- 0.63 vs 6.50 +/- 1.43, 1.83 +/- 0.44 and 1.33 +/- 0.38, respectively), but the ovulation rate remained unchanged after immunization. The average plasma concentration of FSH and estradiol-17beta during the estrous cycle increased significantly (P<0.05) after immunization. These results suggest that immunization against inhibin is a useful tool to increase the number of ovarian follicles during the estrous cycle of pony mares. Moreover, the present study supported the concept that inhibin plays a major role in the control of follicular growth through its inhibitory effect on FSH secretion synergistically with steroid hormones.  相似文献   

5.
This study was designed to explore the effect of active immunization against maltose binding protein‐gonadotropin releasing hormone I hexamer (MBP‐GnRH‐I6) on the reproductive function in cats. Each immunized cat was administered twice intramuscularly in the neck at 16 and 20 weeks old. The concentrations of the testosterone and estradiol and the level of anti‐GnRH‐I antibody in the serum were measured by radioimmunoassay and ELISA, respectively. The results showed that the weight and size of testicles and ovaries, and the concentrations of serum testosterone and estradiol in the immunized animals were lower than those of the control cats (P < 0.05), but that the levels of anti‐GnRH‐I antibody were significant higher compared to control animals (P < 0.05). Testicular tissues from the immunized male cats showed that seminiferous tubules were depauperate with the lumen relatively empty and that the differentiation of spermatogonia was not obvious. Tissues from the immunized female cats showed that the ovaries had many primordial follicles and primary follicles, but no secondary follicle was observed. These results showed active immunization against MBP–GnRH‐I6 could make the gonads atrophy and reduce the concentrations of gonadal hormones, which suggested that MBP‐GnRH‐I6 was a very effective immunogen in the cat.  相似文献   

6.
OBJECTIVE: To examine the immunogenicity of an equine immunocontraceptive vaccine and its efficacy in controlling hormone-related behaviour. DESIGN: A total of 24 mares at two sites in Australia were vaccinated with an immunocontraceptive vaccine comprising gonadotrophin releasing hormone (GnRH) conjugated to a carrier protein in immunostimulating complex as an adjuvant. Twelve animals at each site received a placebo of adjuvant alone and served as controls for seasonal oestrus, hormonal and behaviour patterns. Animals were observed for injection site reactions, ovarian and follicular activity, and serum levels of antibody, 17beta-oestradiol and progesterone in the weeks following vaccination. Mares were also examined for oestrous behaviour by teasing with a stallion. RESULTS: All mares responded to vaccination. Two weeks following the second vaccination there was a peak in antibody response to GnRH that declined gradually over the following weeks. Commensurate with the elevated anti-GnRH antibody there was a marked effect on ovarian activity with a reduction in 17beta-oestradiol and progesterone levels in the 24 vaccinated mares. There was also a reduction of oestrus-related behaviour as determined by a teaser stallion. This effect lasted a minimum of 3 months and correlated with the initial level of antibody response. CONCLUSION: Following a conventional two-dose immunisation regime this commercially available equine immunocontraceptive vaccine was effective at inhibiting oestrous behaviour for at least 3 months. This vaccine has a high level of safety since there were no significant local reactions nor were there any adverse systemic responses to vaccination.  相似文献   

7.
Plasma progesterone levels were measured daily to determine the accuracy of diagnosing ovulation by rectal palpation carried out every other day; 81.5 per cent mares injected with human chorionic gonadotrophin showed increases of progesterone more than 1 ng/ml by 72 h after injection compared with 65 per cent of mares injected with gonadotrophin releasing hormone (GnRH) or saline. Mating at ovulation achieved a 74 per cent pregnancy rate in mares given hCG compared with 50 per cent given GnRH and 45 per cent controls. Diagnosis of ovulation per rectum on the basis of a pit in the ovarian surface or the presence of a soft friable structure was found to be accurate in 91 per cent of cases. Diagnosis based on the presence of a firm plum-like structure or the disappearance of a previously identified follicle at a given site was 60 per cent accurate. In cases of rectal diagnosis of non-ovulation 38 per cent had actually ovulated based on a rise in progesterone more than 1 ng/ml and a further 19 per cent showed a rise in progesterone by 24 h after the diagnosis. The use of hCG may improve conception rates by synchronisation of ovulation and mating and where rectal palpation of the ovaries remains the only basis for timed mating.  相似文献   

8.
Four studies were carried out to determine the ovarian responses of dairy cows undergoing natural oestrous cycles to sequential injections of gonadotrophin-releasing hormone (GnRH), followed seven days later by prostaglandin and, 48 to 72 hours later, by a second injection of GnRH. In study 1, of 60 cows so treated, 47 were in the intended periovulatory phase when a fixed-time insemination was given 72 hours after the prostaglandin. In study 2, detailed observations were made in 32 cows treated as in study 1, using ultrasound to determine the optimum time to administer the second dose of GnRH. Ovulation was most effectively synchronised by giving GnRH 56 to 60 hours after the prostaglandin. Study 3 investigated the timing of ovulation when no initial dose of GnRH was given. Six cows were injected with prostaglandin on day 12 of the oestrous cycle, followed by GnRH 60 hours later. Five of the six cows ovulated 24 to 36 hours after GnRH, an equivalent timing and synchrony to that in study 2, in which a dose of GnRH had been given seven days before prostaglandin. In study 4, an initial dose of GnRH was given to six cows late (day 17) in the oestrous cycle, and prostaglandin seven days later. The GnRH treatment delayed luteolysis in five of the cows so that they were responsive to the prostaglandin and ovulated 24 to 36 hours after the second dose of GnRH. The use of GnRH (day 0) - prostaglandin (day 7) - GnRH (day 9.5) appears to be an effective means of synchronising ovulation in most cows.  相似文献   

9.
There is a need for a safe, effective and practical method of oestrus suppression in the mare. The aim of this study was to monitor ovarian activity in mares exposed to either 9.4 or 28.2 mg deslorelin acetate, a GnRH agonist, in the form of a sustained-release implant. Following oestrus synchronisation, mares were randomly assigned to one of three groups (n = 4 per group) and administered either one (Des1 group; 9.4 mg) or three (Des3 group; 28.2 mg) implants of deslorelin acetate (Suprelorin-12, Virbac Australia) or one blank implant (Control group; Virbac Australia). Mares underwent weekly blood sampling for 12 weeks following implant placement (Day 0–Day 84), with transrectal palpation and ultrasonography of the reproductive tract at all sampling timepoints except Days 56, 70 and 77. All mares showed baseline serum progesterone concentrations (SPC; ≤1.3 nmol/L or 0.4 ng/ml) on Day 0. Cycling Control mares showed typical oestrous cyclicity characterised by peaks and troughs in SPC over time. Four of eight treated mares demonstrated a sustained elevation in SPC after the initial ovulation after implant placement; SPC declined to baseline levels (Des1 group; 2 mares) or remained elevated (Des3 group; 2 mares) at the final sampling timepoint on Day 84. Oestrous cyclicity was erratic in three of the remaining four treated mares. In total, 87.5% (7 of 8) of treated mares showed atypical oestrous cyclicity after implant placement. These results suggest that deslorelin acetate disrupts oestrous cyclicity in the mare, which warrants further research.  相似文献   

10.
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.  相似文献   

11.
Five lighthorse mares were actively immunized against gonadotropin releasing hormone (GnRH) conjugated to bovine serum albumin (BSA) to study the involvement of GnRH in luteinizing hormone (LH) and follicle stimulating hormone (FSH) secretion following ovariectomy (OVX) and after administration of testosterone propionate (TP). Five mares immunized against BSA served as controls. Immunizations were started on November 1, and OVX was performed in June (d 1). All mares were treated with TP from d 50 to 59 after OVX. On the day of OVX, concentrations of LH were lower (P less than .05) in GnRH-immunized mares than in BSA-immunized mares and were generally nondetectable; FSH concentrations were reduced (P less than .05) by 50% in GnRH-immunized mares relative to BSA-immunized mares. In contrast to BSA-immunized mares, plasma concentrations of LH or FSH did not increase after OVX in GnRH-immunized mares. The LH response to GnRH analog (less than .1% cross-reactive with GnRH antibodies) on d 50 was reduced (P less than .05) by 97% in GnRH-immunized mares relative to BSA-immunized mares, whereas the FSH response was similar for both groups. Treatment with TP for 10 d reduced (P less than .01) the LH response and increased (P less than .01) the FSH response to GnRH analog in BSA-immunized mares, but it had no effect (P greater than .1) on the response of either gonadotropin in GnRH-immunized mares.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

12.
We performed a standing hand-assisted laparoscopic ovariectomy in a draft mare that presented with high serum anti-Müllerian hormone (AMH) level and had an enlarged single cystic ovary. Histopathological examination revealed no tumor cell proliferation in the ovary, but the presence of a large ovarian cyst was confirmed. In the diagnosis of abnormal ovaries in mares, a comprehensive assessment should be performed, including the monitoring of ovarian morphology and biomarkers over time, to determine the disease prognosis and treatment plan. The case of this mare with a nonneoplastic abnormal ovary and increased serum AMH level was rare. We suggest that standing hand-assisted laparoscopic ovariectomy is useful for the removal of large ovaries in draft mares.  相似文献   

13.
This study investigated the efficacy of two dosage regimens of a potent GnRH analogue (GnRHa), deslorelin acetate, in inducing ovulation in seasonally anestrous mares. Forty-five seasonally anestrous mares were randomly assigned according to follicular size to one of three treatment groups: control, increasing GnRHa dose, and constant GnRHa dose. Treatment began on February 28 and continued until ovulation or for a maximum of seven treatments. Mares were palpated every other day until a 35 mm follicle was detected, then every day until ovulation or regression of the follicle occurred. Blood samples were taken from five randomly chosen mares in each treatment group and analyzed for LH levels.Twenty percent of mares in both deslorelin treatment groups ovulated, while no control mares ovulated during the treatment period. There was no difference in the number of mares that ovulated between treatment groups. Four of the six mares that ovulated were in transitional anestrus at the initiation of treatment, while only two were in deep anestrus.Concentrations of LH were greater (p=0.0008) in both GnRH-treated groups than in the control mares. Concentrations of LH did not differ between the two GnRH-treated groups until day 12 of treatment, when mares treated with a constant dosage had higher (p=0.0358) levels of LH than those treated with an increasing dosage. It is possible that administration of larger amounts of the GnRH agonist lowered the sensitivity of the pituitary to stimulation by GnRH.Deslorelin acetate did stimulate follicular growth and ovulation in a limited number of anestrous mares. Further investigation into the potential of this short-term implant to shorten the onsent of the breeding season is recommended.  相似文献   

14.
Mares that had previously been fed to attain body condition scores (BCS) of 7.5 to 8.5 (high) or 3.0 to 3.5 (low) were used to determine the interaction of BCS with the responses to 1) administration of equine somatotropin (eST) daily for 14 d beginning January 20 followed by administration of GnRH analog (GnRHa) daily for 21 d and 2) 4-d treatment with dexamethasone later in the spring when mares in low BCS had begun to ovulate. The majority of mares with high BCS continued to cycle throughout the winter, as evidenced by larger ovaries (P < 0.002), more corpora lutea (P < 0.05), greater progesterone concentrations during eST treatment (P < 0.04), and more (P < 0.05) large- and medium-sized follicles. Treatment with eST alone or in combination with GnRHa had no effect (P > 0.05) on ovarian activity or ovulation. Plasma leptin concentrations were greater (P < 0.002) in mares with high BCS; however, there was no effect (P > 0.10) of eST treatment. Plasma IGF-I concentrations were greater (P < 0.0001) in mares treated with eST compared with mares given vehicle, and mares with high BCS had greater IGF-I (P < 0.02) and LH concentrations (P < 0.02) than mares with low BCS. Plasma leptin concentrations in mares with high BCS were increased (P < 0.001) within 12 h of dexamethasone treatment; the leptin response (P < 0.001) in mares with low BCS was greatly reduced (P < 0.001) and transient. Glucose and insulin concentrations also increased (P < 0.0001) after dexamethasone treatment in both groups, and the magnitude of the response was greater (P < 0.0001) in mares with high BCS than in mares with low BCS. In summary,low BCS in mares was associated with a consistent seasonal anovulatory state that was affected little by eST and GnRHa administration. In contrast, all but one mare with high BCS continued to experience estrous cycles and(or) have abundant follicular activity on their ovaries. The IGF-I response to eST treatment was also reduced in mares with low BCS, as was the basal leptin concentration and leptin response to dexamethasone. Although low BCS and leptin concentrations were associated with inactive ovaries during winter and early spring, mares with low BCS eventually ovulated in April and May while leptin concentrations remained low.  相似文献   

15.
Forty-six adult merino ewes were immunised against oestradiol-17 beta-6 carbomethyloxime:human serum albumin and 48 comparable ewes were used as controls in an experiment to study the effects of gonadotrophin releasing hormone (GnRH) on ovulatory responses after treatment with pregnant mare's serum gonadotrophin (PMSG). All the ewes were treated with progestogen sponges for 14 days and received 1500 iu PMSG on the 12th day. Twenty-four control and 24 immunised ewes received 25 micrograms GnRH 21.5 hours and 23 hours after the sponges were withdrawn. Plasma samples were collected between 17 and 50 hours after the sponges were withdrawn and assayed for luteinising hormone (LH). Immunisation reduced the proportion of ewes which ovulated and their rate of ovulation. Injection of GnRH increased the proportion of immunised ewes ovulating (P less than 0.0005) and their rate of ovulation (P less than 0.0001). More unovulated follicles were observed in immunised ewes regardless of GnRH treatment (P less than 0.0001). The rate of recovery of eggs was reduced after immunisation. Treatment with GnRH produced a surge of LH of equal magnitude in the control and immunised ewes although not as many immunised ewes ovulated.  相似文献   

16.
We purified the protein antigen (P64), which contains 66 and 64 kDa proteins, from the alkaline extract (AE) of whole cells of Erysipelothrix rhusiopathiae strain Agata (serovar 5) to determine the protective activity of the antigen against E. rhusiopathiae infection in pigs. The serum titre of antibody against P64 rapidly increased in pigs immunized with 500 and 100 micrograms of P64 and reached maximum values at 3 weeks after the first immunization (1 week after the second immunization). However, the serum antibody titres were not increased in pigs immunized with 20 micrograms of P64 and in nonimmunized pigs. In the pigs immunized with live cell vaccine (acriflavin-fast attenuated strain Koganei 65-0.15), the serum titres of antibody against P64 also increased at 1-2 weeks after immunization. In a pig challenge test performed on immunized and nonimmunized pigs, all nonimmunized pigs showed typical clinical signs of swine erysipelas (fever, erysipeloid, arthritis), while all pigs immunized with 500 and 100 micrograms of P64 and live cell vaccine showed no clinical signs of this disease. In Western blot analysis, sera from pigs immunized with P64 and live cell vaccine strongly reacted with the 64 kDa protein. In contrast, the serum from nonimmunized pigs did not react with any proteins. From these results, it was suggested that a specific antibody against the 64 kDa protein could be increased in pigs immunized with P64 or live cell vaccine and that this anti-P64 antibody has a strong protective effect against E. rhusiopathiae infection in pigs.  相似文献   

17.
A DNA vaccine expressing glycoprotein C (gC) of bovine herpesvirus-1 (BHV-1) was evaluated for inducing immunity in bovines. The plasmid encoding gC of BHV-1 was injected six times intramuscularly or intradermally into calves at monthly intervals. After immunization by both routes neutralizing antibody and lymphoproliferative responses developed. The responses in the intradermally immunized calves were better than those in calves immunized intramuscularly. However, the intradermal (i.d.) route was found to be less efficacious when protection against BHV-1 challenge was compared. Following intranasal BHV-1 challenge, all immunized calves demonstrated a rise in IgG antibody titre on day 3, indicating an anamnestic response. The control non-immunized calf developed a neutralizing antibody response on day 7 post-challenge. The immunized calves showed a slight rise in temperature and mild clinical symptoms after challenge. The intramuscularly immunized calves showed earlier clearance of challenge virus compared with intradermally immunized calves. These results indicate that DNA immunization with gC could induce neutralizing antibody and lymphoproliferative responses with BHV-1 responsive memory B cells in bovines. However, the immunity developed was not sufficient to protect calves completely from BHV-1 challenge.  相似文献   

18.
The aim of the present study was to examine the plasma concentrations of progesterone, oestradiol-17beta and cortisol in the cows with cystic follicle and to examine its relationship with the ovulatory response to gonadotropin-releasing hormone (GnRH). Eighty-five post-partum Holstein-Friesian cows with cystic follicles regardless of the presence of corpus luteum were studied. Follicular size, presence of corpus luteum and occurrence of ovulation were checked by palpation per rectum. Blood collection and palpation per rectum were conducted on days 0, 7 and 14. Gonadotropin-releasing hormone was administered at day 7. Plasma concentrations of progesterone, oestradiol-17beta and cortisol were determined. Progesterone concentrations of <3.2, 3.2-4.8 and >4.8 nmol/l were defined as low, intermediate and high, respectively. Sixty-three (74.1%) of 85 cows showed low (<3.2 nmol/l =1 ng/ml) progesterone concentrations on day 0. Only 40 (47.1%) of them showed low-low pattern of progesterone at days 0 and 7. In 27 (31.8%) of them, progesterone concentration had increased by day 14. Of 22 cows having high progesterone concentration (>/=4.8 nmol/l) on day 0, corpus luteum was not detected in 18 cows (21.2%). Only in 10 cows, cystic follicle disappeared after GnRH administration. However, only one of 27 cows in which progesterone pattern was low-low-high at days 0, 7 and 14 experienced ovulation of the cystic follicle. Significantly lower oestradiol-17beta concentration was found on day 7 in cows showing a low-low-low pattern than a low-low-high pattern of progesterone (43.0 +/- 4.6 vs 55.8 +/- 2.8 pmol/l, p < 0.05). There was no significant difference in cortisol concentration on any days (days 0, 7 and 14) between cows showing a low-low-low and low-low-high pattern of progesterone. These results suggest that approximately one-fifth of cows diagnosed to have ovarian cysts possess luteal cysts and that a high oestradiol-17beta concentration at the time of GnRH administration is involved in the subsequent ovulation of the follicle, although ovulated follicle may not be cystic.  相似文献   

19.
Effects of testosterone propionate (TP) treatment on plasma concentrations of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) before and after an injection of gonadotropin releasing hormone (GnRH) were studied using ovariectomized cows and pony mares. An initial injection of GnRH (1 microgram/kg of body weight) was followed by either TP treatment or control injections for 10 (cows) or 11 (ponies) d. A second GnRH injection was administered 1 d after the last TP or oil injection. Concentrations of LH and FSH were determined in samples of plasma taken before and after each GnRH injection. Control injections did not alter the response to GnRH (area under curve) nor the pre-GnRH concentrations of LH and FSH in ovariectomized cows or ponies. Testosterone treatment increased (P less than .01) the FSH release in response to GnRH in ovariectomized mares by 4.9-fold; there was no effect in cows, even though average daily testosterone concentrations were 59% higher than in pony mares. Testosterone treatment reduced the LH release in response to GnRH by 26% in ovariectomized mares (P less than .05) and by 17% in ovariectomized cows (P approximately equal to .051). These results are consistent with a model that involves ovarian androgens in the regulation of FSH secretion in the estrous cycle of the mare, but do not support such a model in the cow.  相似文献   

20.
Antiserum generated in a horse against testosterone conjugated to bovine serum albumin (BSA) was administered to six lighthorse mares (androgen-immunized mares) 1 to 3 d before a prostaglandin-induced estrus and twice again at 2-d intervals. Six control mares were administered antiserum generated against BSA on the same schedule. Relative to testosterone, cross-reactivities of other steroids with the testosterone antiserum were (%): dihydrotestosterone, 52; 5 alpha-androstane-3 alpha,17 beta-diol, 8.6; androst-4-ene-3,17-dione, 1.2; and all others tested less than .1. Tritiated testosterone binding in plasma increased (P less than .01) in androgen-immunized mares within 1 h and remained elevated (P less than .01) relative to controls for greater than 21 d. There was no effect (P greater than .10) of passive immunization against androgen on interval to estrus after prostaglandin injection, duration of estrus, ovarian volume, number of palpable follicles or follicular volume during estrus. In contrast, concentrations of luteinizing hormone (LH) were higher (P less than .05) in androgen-immunized mares than in control mares during estrus and early diestrus. Concentrations of follicle stimulating hormone (FSH) and progesterone at those times were not affected (P greater than .10). From these data, we conclude that androgens in the mare during estrus may be involved with the regulation of LH secretion. In contrast, no involvement with FSH secretion was apparent under these short-term conditions.  相似文献   

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