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1.
The incidence of hemorrhagic anovulatory follicles (HAFs) is approximately 5% and 20% of estrous cycles during the early and late ovulatory season, respectively. The structures are more common in old mares (eg, >20 years), tend to occur repeatedly in individuals, and occur most frequently during the late follicular phase. In a recent study, the day of ovulation in controls and the first day of HAF formation, as indicated by cloudiness of follicular fluid, were defined as day 0. On day -1, future ovulating and HAF groups did not differ in follicle diameter or in the frequency of discrete gray-scale ultrasonic indicators of impending ovulation; however, in future HAFs, a greater percentage of the circumference of the follicle exhibited color-Doppler signals of blood flow. No differences were found between the two groups in systemic concentrations of progesterone, luteinizing hormone (LH), and follicle-stimulating hormone (FSH) on days -4 to 2, but estradiol was elevated in the HAF group on day -3. The wall of the HAFs developed well-vascularized luteal tissue as indicated by echotexture and color Doppler signals and by the production of near normal levels of progesterone. In conclusion, HAFs formed from viable preovulatory follicles that did not differ from ovulatory follicles in diameter or gray-scale echotexture. Estradiol concentrations were elevated a few days before the failure of ovulation, and the wall of the follicle was more extensively vascularized on day -1.  相似文献   

2.
The most common pathological anovulatory condition that occurs spontaneously during the breeding season in the mare is the haemorrhagic anovulatory follicle (HAF). A relatively high proportion of mares, soon after ovulation, develop a corpus haemorrhagicum (CH) with a central lacuna. This type of corpora lutea may resemble an HAF, which may complicate the accurate diagnosis of ovulation. The main objective of this study was to compare the ultrasound data of mares examined frequently with HAFs and CHs to elucidate whether it is possible to distinguish them from each other. A total of 135 ovulating mares were classified according to the morphology of the corpus luteum (CL) in mares with: a solid CL, a CH with small or with large central cavities. Ultrasound characteristics of the development of 11 HAF and 13 CHs with a large central cavity were compared. The pre‐ovulatory follicular diameter of ovulatory mares was significantly correlated with the diameter of CH with large central cavities. The percentage of mares with post‐ovulatory areas eligible to be mistaken with a CH was <25%. Although a predictive diagnosis of an HAF/CH can be made on the basis of several ultrasonographic endpoints, the only parameter that allows a definitive diagnosis is the thickness of the luteal border. This is <3 mm in HAFs in contrast to >5 mm in CHs. However, this only applies when the unidentified structure has non‐organized contents.  相似文献   

3.
Reproductive records of the entire lives of two mares with abnormally high incidence of multiple ovulation and hemorrhagic anovulatory follicles were analyzed retrospectively. Chi-square analysis was used to test statistically the effect of cloprostenol, a prostaglandin F2 analog, on the incidence of multiple ovulations, hemorrhagic anovulatory follicles, and its ultrasonographic appearance. A total of 319 estrous cycles during a 17-year period were analyzed. Cycles induced with cloprostenol were more likely (P < .000) to develop hemorrhagic anovulatory follicles than spontaneous cycles. The incidence of multiple ovulation was higher in induced cycles than in spontaneous cycles in one of the two mares.  相似文献   

4.
Reason for performing study: To improve efficiency at the farm level, a better understanding of how farm management factors impact reproductive performance is important. Objective: To assess reproductive efficiency and effectiveness among Thoroughbred mares in central Kentucky. Methods: A cohort of 1011 mares on 13 farms in central Kentucky was followed during the 2004 mating and 2005 foaling season. Information on farm level practices was collected via interviews with farm managers. Reproductive records were collected for each mare mated to obtain information on mare characteristics. The influence of mare age and status (maiden, foaling, barren) on Days 15 and 40 post mating pregnancy rates, foaling rates and total effective length of the mating season were assessed. The influence of stallion book size on reproductive performance measures was also examined. Results: Per season pregnancy rates on Days 15 and 40 post mating and live foal rate were 92.1, 89.3 and 78.3%, respectively. Per cycle rates for the same time periods were 64.0, 58.3 and 50.8%. There were no significant associations between stallion book size and reproductive performance outcomes. The mean s.d. interval from the beginning of the mating season to the last mating of the mare was 36.5 ± 26.1 days. Conclusions: Mare age had a significant impact on efficiency of becoming pregnant, maintaining pregnancy and producing a live foal. Overall, fertility did not decrease among stallions with the largest book sizes. Total interval length of the mating season can be reduced if managers ensure maiden and barren mares are mated at the beginning of the season and foaling mares are mated at the earliest oestrus after acceptable uterine involution has been achieved. Potential relevance: Measures identified in the study can be used by owners, farm managers and veterinarians to improve mare reproductive performance and identify parameters to assist with the implementation of effective culling practices.  相似文献   

5.
Stallion-like sexual behavior in mares is rare, except in association with ovarian tumors or hormonal treatments. The rarity of the phenomenon was confirmed in a recent 3-year study. The mean number of mares with detected stallion-like behavior, including mounting with thrusts, during an entire ovulatory season was 5.7 (17/3 years) in a herd averaging 105 mares (5% incidence/mare/season). From a total of 17 mountings of an estrous mare by another mare, 15 occurred when the mounting mare was in the follicular phase and two when in the early luteal phase. Plasma testosterone concentration on the day of mounting was higher (P < 0.01) in the mounting mares (17.7 ± 2.3 pg/ml) than in the standing mares (10.9 ± 0.5 pg/ml). No other deviation in the endocrine, behavioral, or morphologic aspects of the estrous cycle was observed. In another study, testosterone was assayed daily from 7 days before to 4 days after ovulation in seven mares during estrous cycles with no detected mare-on-mare mountings. Concentrations during the follicular phase were highest on the days corresponding to when mare-on-mare mounting was detected in the previous study. It is concluded that the rare occurrence of stallion behavior by untreated mares with no detected ovarian tumors is a consequence of an unusually high, apparently transient fluctuation in circulating testosterone at the time of mounting.  相似文献   

6.
OBJECTIVE: To identify factors associated with excessive proportions of early fetal losses associated with mare reproductive loss syndrome in central Kentucky during 2001. DESIGN: Case-control study. PROCEDURE: Questionnaires were used to collect information on farm-, pasture-, and individual animal-level factors purportedly associated with mare reproductive loss syndrome. Data were collected for 133 farms (97 with excessive proportions of early feta losses and 36 control farms) representing 6,576 mares. RESULTS: Factors significantly associated with an increased risk of excessive early fetal losses were exposure to moderate to high concentrations of Eastern tent caterpillars, exposure to cherry trees, farm size > or = 50 broodmares, being bred during February 2001, and frequent exposure to waterfowl. Feeding hay to mares outside was associated with a decreased risk of excessive proportions of early fetal losses. Pasture composition and management factors were not significantly different between affected and control pastures. Individual animal-level factors were investigated on 6 farms representing 340 mares, and age, parity, and pre- and postbreeding treatments were not significantly associated with risk of early fetal loss. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that limiting exposure to Eastern tent caterpillars and cherry trees and feeding hay to mares outside may help decrease the risk of excessive proportions of early fetal losses associated with mare reproductive loss syndrome.  相似文献   

7.
Hydrallantois in the mare is a very rare condition, and clinical reports help to gather information to elucidate its pathogenesis, treatment options and prognosis. Five different cases of hydrallantois in the mare are reported in this article, all with the involvement of placentitis. The five mares were presented because of acute distention of the abdomen, dyspnoea, stiff gait and a lack of appetite. After a gradual release of the excessive amount of allantoic fluid, an abortion was induced in all five mares. The foals were either born dead or euthanized. The mares recovered quickly. One mare conceived within the same season, one remained barren despite several cycles of natural breeding, and no data were available on the other three mares. In this series, the condition is reported for the first time in two Shetland ponies, both pregnant with foals sharing a close genetic background. In both cases, the condition led to hyperlipidemia. The condition as it occurs in nulliparous mares is also discussed. Finally, the possible involvement of placentitis in the pathogenesis is emphasized.  相似文献   

8.
OBJECTIVE: To characterize the temporality of dates of breeding and abortion classified as mare reproductive loss syndrome (MRLS) among mares with abortions during early gestation. ANIMALS: 2,314 mares confirmed pregnant at approximately 28 days after breeding from 36 farms in central Kentucky, including 515 mares that had early-term abortions. PROCEDURE: Farm veterinarians and managers were interviewed to obtain data for each mare that was known to be pregnant to determine pregnancy status, breeding date, last date known to be pregnant, and date of abortion. RESULTS: Mares bred prior to April 1, 2001, appeared to be at greatest risk of early-term abortion, both among and within individual farms. Mares bred in mid-February appeared to be at greatest risk of abortion, with an estimated weekly incidence rate of abortion of 66% (95% CI, 52% to 80%). CONCLUSIONS AND CLINICAL RELEVANCE: Mares in central Kentucky bred between mid-February and early March were observed to be at greatest risk of early-term abortion, and risk gradually decreased to a background incidence of abortion of approximately 11%. Mares bred after April 1, 2001, appeared to be at markedly less risk, indicating that exposure to the cause of MRLS likely occurred prior to this date.  相似文献   

9.
Horse owners want to have their mares bred as early as possible in the breeding season after February 1. Numerous medical treatments, such as progesterone, dopamine antagonists, and gonadotropin-releasing hormone have been administered to anestrous or transitional mares in an attempt to induce follicular development. Some of these treatments are ineffective or impractical, so there is a need in the horse industry to develop alternative techniques to stimulate follicular development and ovulation early in the breeding season. Twenty transitional mares were assigned to one of two treatment groups. Mares in group 1 (n = 10) served as untreated controls, and mares in group 2 (n = 10) were administered 12.5 mg of purified equine follicle-stimulating hormone (eFSH) (Bioniche Animal Health USA, Inc., Athens, Ga) intramuscularly twice daily for a maximum of 15 consecutive days. Mares were considered to be in transition when the diameter of the largest follicle was ≥25 mm. Once one or more follicles >35 mm were detected, eFSH treatment was discontinued and human chorionic gonadotropin was administered intravenously. The percentage of mares ovulating during the 15-day observation period was compared by means of chi-square analysis. The interval to ovulation and the number of ovulations per mare were compared between the two groups by Student t test. In 8 of 10 mares treated with eFSH follicles developed and ovulation occurred during the 15-day observation period, compared with 0 of 10 control mares. Interval from onset of treatment to ovulation was 7.6 ± 2.4 days for these eight mares. The eight mares were treated for an average of 5.2 ± 1.3 days with eFSH. Thus, the eFSH treatment was effective in advancing the first ovulation of the year in transitional mares.  相似文献   

10.
Abstract

AIM: The objective of this study was to utilise multivariable statistical methods appropriate for clustered data to identify mare-related explanatory variables that significantly affected the reproductive performance of Thoroughbred mares in the Waikato region of New Zealand. In addition, we aimed to determine the relative contribution of the mare, stallion and stud farm to reproductive performance.

METHODS: A prospective cohort study was performed involving five stud farms in the Waikato region of New Zealand during three consecutive breeding seasons (2006–2008). A total of 1,482 individual mares contributed 2007 mare years and 3,402 oestrous cycles over the three breeding seasons. Reproductive performance was measured using three parameters; (a) first-cycle pregnancy rate (FCPR), (b) end-of-season pregnancy rate (SPR), and (c) the start-of-mating to conception interval.

RESULTS: When controlled for the effects of serving stallion, stud farm and year of study the only significant mare-related variables included in the final models of FCPR, SPR and conception interval were the age of the mare and her reproductive status (classified as dry or foaling). Advancing mare age significantly reduced reproductive performance regardless of reproductive status and foaling mares had significantly poorer reproductive outcomes compared with dry mares when controlled for age. For each additional increase in year of age, the FCPR was reduced by a factor of 0.94 (95% CI=0.92–0.96) and the SPR was reduced by a factor of 0.91 (95% CI=0.88–0.93). Mares older than 14 years of age took longer to conceive after the start-of-mating compared with younger mares. The daily hazard of conception for mares 14 years and older was 0.64 (95% CI=0.47–0.83) times less than mares younger than 9 years of age. Determining the relative contribution of the mare, stallion and stud farm to the FCPR indicated that 95.9% of the variation was at the mare level, 4.1% was at the stallion level and 0% was at the stud farm level. For the SPR the variance components indicated that 92.5% of the variation was at the mare level, 6.7% was at the stallion level and 0.8% was at the stud farm level.

CONCLUSIONS: The reproductive performance of Thoroughbred mares in the Waikato region of New Zealand is influenced by two main mare-related factors; the age of the mare and her reproductive status (dry or foaling). The majority of variation in reproductive performance was associated with mare-level factors and the contribution of the stallion and stud farm was relatively minor.  相似文献   

11.
AIM: To determine the effect of hCG administration to cycling Thoroughbred mares, on pregnancy and twinning rates and the number of serves in the treated cycle. METHODS: A retrospective case control approach was conducted involving 2119 mare ovulatory cycles, on 1110 mares over a 7-year period. Data were collected by 1 of the authors during routine stud work at 3 commercial Thoroughbred farms in the Waikato region of New Zealand. The hCG (1500 IU) was administered by intravenous injection to selected mares 24 h before the expected time of breeding. Mares were scanned for pregnancy (singleton or twins) 14 days after the onset of dioestrus or detection of ovulation. Multilevel logistic regression analyses were used to identify the risk factors associated with the outcomes of interest while simultaneously controlling for possible confounding factors. RESULTS: Treatment with hCG tended to improve the odds of pregnancy (p=0.06), produced a 3-fold increase in the odds of twins (p<0.001), and increased the odds of a mare having a single serve in the treated ovulatory cycle (p=0.036). The first ovulatory cycle of a season in which a mare was bred was associated with a lower odds of pregnancy (p=0.02), and a lower odds of twins (p=0.003), when compared with subsequent cycles. Lactating mares were less likely to be diagnosed with twins (p=0.005), and were more likely to have a single serve (p<0.001), in any one ovulatory cycle than non-lactating mares. CONCLUSIONS: This report supports the role of hCG as an important therapeutic tool in veterinary management of broodmares for optimal reproductive performance. Mares treated with hCG must be managed in the knowledge that they have an increased likelihood of twins.  相似文献   

12.
Reason for performing study: There have been no studies reporting the impact of reproductive efficiency and mare financial value on economic returns. Objective: To explore the economic consequences of differences in reproductive efficiency over time in the Thoroughbred mare. Methods: Complete production records for 1176 mares were obtained. Production history and drift in foaling date were calculated. Multiple logistic regression was used to identify factors influencing the probability of producing a registered foal in 2005. The ‘net present value’ and ‘internal rate of return’ were calculated for economic scenarios involving different initial mare financial values, levels of reproductive efficiency, and durations of investment. Results: Among mares that did not produce a foal every year (63%), the mean time before failing to produce a registered foal was 3.4 years. The majority of mares drifted later in their foaling dates in subsequent foaling seasons. Increasing mare age, foaling after 1st April, needing to be mated multiple times during the season, and producing a lower number of foals in continuous sequence during previous years decreased the probability of producing a registered foal. Over a 7 year investment period, live foals must be produced in all but one year to yield a positive financial return. Profitability was highest among mares of greatest financial value. Conclusions: Mares are long‐term investments due to the extended period before there is a return on the investment. Improving our understanding of mare, stallion and management factors that affect the likelihood of producing a live foal are critical to ensuring a positive financial return. Additional work is needed to test the robustness of the study's conclusions when the cost and revenue assumptions are varied. Potential relevance: This information can assist in assessing mare profitability and developing management strategies to maximise profitability.  相似文献   

13.
OBJECTIVE: To identify factors associated with abortions of mares during late gestation attributed to mare reproductive loss syndrome (MRLS). DESIGN: Case-control study. ANIMALS: 282 broodmares from 62 farms in central Kentucky, including 137 mares that had late-term abortions (LTAs) associated with MRLS, 98 mares from the same farms that did not abort, and 48 mares that aborted from causes other than MRLS. PROCEDURE: Farm managers were interviewed to obtain data on a wide range of management practices and environmental exposures for the mares. Data for case and control horses were compared to identify risk factors for a mare having a MRLS-associated LTA (MRLS-LTA). RESULTS: Several factors increased the risk of mares having MRLS-LTAs, including increased amount of time at pasture, less time in a stall, feeding concentrate on the ground, higher proportion of diet derived from grazing pasture, being fed in pasture exclusively during the 4-week period prior to abortion, access to pasture after midnight during the 4-week period prior to abortion, and drinking from a water trough or not having access to water buckets or automatic waterers. CONCLUSIONS AND CLINICAL RELEVANCE: Analysis indicates that exposure to pasture predisposed mares to having MRLS-LTAs and stillborn foals. Methods for limiting exposure to pasture (keeping mares in stalls longer) during environmental conditions similar to those seen in 2001 should reduce the risk of mares having MRLS-LTAs.  相似文献   

14.
Unsolicited reports of estrous behavior in mares thought to be pregnant were received from owners or caretakers of Arabian mares. Estrous behavior was confirmed and mares were examined for pregnancy. Gender of the conceptus was determined at foaling in 11 mares in which estrous behavior was confirmed while an apparently viable, ultrasonically normal-appearing conceptus was present. In 9 mares in which the day of ovulation was known (Day 0), the estrous behavior occurred on Day 12, 13 or 14 (5 mares), Day 18 or 20 (2 mares), Day 40 (1 mare) and Day 60 (1 mare). In another study, 55 pony mares were observed for estrous behavior every 3 days for 20 minutes during Days 11 to 40. Estrous behavior was observed in 1 mare (2%) on Day 24. Combined for the 2 studies, the incidence of a female conceptus (12/12) was greater (P<0.01) than the incidence of a male conceptus (0/12) in mares that exhibited estrous behavior.  相似文献   

15.
Pituitary and serum from 86 male or female horses of various reproductive states were collected in the normal breeding season (summer) and in the nonbreeding season (winter) at a commercial slaughterhouse. Concentrations of prolactin (PRL), luteinizing hormone (LH) and follicle stimulating hormone (FSH) were measured by radioimmunoassay. Concentrations of pregnant mare serum gonadotropin and reproductive steroids in serum and gross appearance of the reproductive tract and gonads were used to catagorize reproductive state. Concentrations of PRL were higher (P less than .01) in summer than in winter in pituitary and serum of mares, stallions and geldings. In summer, mares had higher (P less than .01) concentrations of PRL in serum than stallions. In mares, concentrations of LH in pituitary were higher (P less than .05) in summer than in winter. Concentrations of LH in serum were higher (P less than .01) in summer than in winter in mares and geldings, higher (P less than .01) in mares than in stallions in summer, higher (P less than .01) in geldings than in stallions in summer and higher (P less than .01) in mares with low serum progesterone (P) concentrations than in mares with high P concentrations in summer. Concentrations of FSH in pituitary and serum did not differ between summer and winter for any type of horse.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

16.
REASONS FOR PERFORMING STUDY: In the mare, ultrasound-guided transvaginal oocyte recovery and transfer might offer a way to circumvent the demanding procedures of in vitro embryo production. Before clinical application, the possible consequences for subsequent fertility have to be considered. OBJECTIVES: To examine ovarian function and morphology in mares after repeated follicular punctures. METHODS: A total of 14-26 follicular puncture sessions were conducted on each of 4 Norwegian pony mares over a period of 8 years. The ovaries of these mares were recovered by bilateral ovariectomy or at post mortem and subjected to macroscopic inspection and histology. For comparison, ovaries were collected from 7 nonaspirated control mares and processed for histology. RESULTS: In all experimental mares, ovarian function, defined as the ability regularly to ovulate preovulatory follicles and develop corpora lutea, remained normal during their last breeding season. Gross examination and histology showed that normal follicular and corpus luteum development was accompanied by the formation of condensed reparative fibrosis and normal local haemosiderosis of the ovarian stroma in all experimental mares. In one mare, an ovary contained several foci of chronic apostematous oophoritis, while a cystic structure lined with a single layer of epithelial-like cells and surrounded by a cartilaginous capsule was present in the other ovary. CONCLUSIONS AND POTENTIAL RELEVANCE: Repeated follicular aspirations do not hamper future folliculogenesis, ovulation and corpus luteum formation. However, ovarian puncture induces reparative fibrosis in the ovarian stroma and involves a risk of inducing abscess formation within the ovarian tissue which may impair fertility.  相似文献   

17.
The presence of anovulatory haemorrhagic follicles during the oestrous cycle of mares causes financial impacts, slowing conception and increasing the number of services per pregnancy. Non‐steroidal anti‐inflammatory drugs (NSAIDs) such as meloxicam and phenylbutazone are used in the treatment of several disorders in mares, and these drugs can impair the formation of prostaglandins (PGs) and consequently interfere with reproductive activity. This study aimed to evaluate the effects of treatment with NSAIDs on the development of pre‐ovulatory follicles in mares. In total, 11 mares were studied over three consecutive oestrous cycles, and gynaecological and ultrasound examinations were performed every 12 h. When 32‐mm‐diameter follicles were detected, 1 mg of deslorelin was administered to induce ovulation. The first cycle was used as a control, and the mares received only a dose of deslorelin. In the subsequent cycles, in addition to receiving the same dose of deslorelin, each mare was treated with NSAIDs. In the second cycle, 4.4 mg/kg of phenylbutazone was administered, and in the third cycle, 0.6 mg/kg of meloxicam was administered once a day until ovulation or the beginning of follicular haemorrhage. All of the mares ovulated between 36 and 48 h after the induction in the control cycle. In the meloxicam cycle, 10 mares (92%) did not ovulate, while in the phenylbutazone cycle, nine mares (83%) did not ovulate. In both treatments, intrafollicular hyperechoic spots indicative of haemorrhagic follicles were observed on ultrasound. Thus, our results suggested that treatment with meloxicam and phenylbutazone at therapeutic doses induced intrafollicular haemorrhage and luteinization of anovulatory follicles.  相似文献   

18.
Previous research from our laboratory showed that approximately one third of obese, nonfoaling mares displayed a condition of hyperleptinemia coupled with hyperinsulinemia that resembled type 2 diabetes in humans. The current study was performed to evaluate the prevalence of the hyperleptinemic syndrome in lactating mares and its possible impact on their rebreeding success. Additionally, we investigated possible relationships between leptin levels in lactating versus nonlactating mares. In experiment 1, jugular blood samples were collected from 198 lactating mares on two occasions approximately 2 weeks apart. The mares resided on eight farms in Louisiana; breeds included Thoroughbred (n = 86), Quarter Horse (n = 71), Warmblood (n = 24), and draft-type (n = 17). Body condition scores (BCS) were measured at the time of blood sampling; plasma samples were assessed for leptin and progesterone concentrations. Reproductive and medical histories, as well as feeding regimens, were compiled on each mare. Based on our previous reports and examination of the current data, a mare was considered hyperleptinemic if her plasma samples contained greater than10 ng/mL leptin; normal was considered 6.0 ng/mL or less; mares with levels above 6.0 and 10 ng/mL or greater were classified as intermediate. Overall mean leptin concentration was 4.7 ng/mL, and average BCS was 5.5. After analysis, 24 mares were classified as hyperleptinemic (12%), 138 were classified as normal (70%), and 36 were classified as intermediate (18%). Leptin concentrations were affected by BCS (P = .08), with higher concentrations in mares with higher body condition; however, there were hyperleptinemic mares with BCS of 4 to 5.5. Feeding regimen affected leptin concentrations (P < .01), with mares on pasture full-time having the highest concentrations. There was no effect of breed, mare age, number of years the mare had been bred, number of live foals, progesterone concentrations, or last foaling date on leptin concentrations. Rebreeding success averaged 81% overall and was not affected by leptin classification. In experiment 2, nonfoaling mares kept on pasture had mean leptin concentrations of 7.0 ng/mL; 8 of 31 mares (26%) displayed hyperleptinemia. Mean leptin concentration was correlated with BCS (R2 = 0.65; P < .02) but was not affected by age of the mare. It was concluded that the hyperleptinemic condition occurs in lactating broodmares, even at BCS as low as 4. The overall incidence appears to be lower in broodmares than in nonfoaling mares, likely because of their lower BCS in general and the energy demands of lactation. Hyperleptinemia did not affect rebreeding success at the end of the breeding season.  相似文献   

19.
An experiment was conducted to determine the effects of high vs low body condition scores (BCS) produced by restricted feeding on reproductive characteristics, hormonal secretion, and leptin concentrations in mares during the autumnal transition and winter anovulatory period. Mares with BCS of 6.5 to 8.0 were maintained on pasture and/or grass hay, and starting in September, were full fed or restricted to produce BCS of 7.5 to 8.5 (high) or 3.0 to 3.5 (low) by December. All but one mare with high BCS continued to ovulate or have follicular activity during the winter, whereas mares with low BCS went reproductively quiescent. Plasma leptin concentrations varied widely before the onset of restriction, even though all mares were in good body condition. During the experiment, leptin concentrations gradually decreased (P < 0.0001) over time in both groups, but were higher (P < 0.009) in mares with high vs low BCS after 6 wk of restriction, regardless of initial concentration. No differences (P > 0.1) between groups were detected for plasma concentrations of LH, FSH, TSH, GH, glucose, or insulin in samples collected weekly; in contrast, plasma prolactin concentrations were higher (P < 0.02) in mares with high BCS, but also decreased over time (P < 0.008). Plasma IGF-I concentrations tended (P = 0.1) to be greater in mares with high vs low BCS. The prolactin response to sulpiride injection on January 7 did not differ (P > 0.1) between groups. During 12 h of frequent blood sampling on January 12, LH concentrations were higher (P < 0.0001), whereas GH concentrations (P < 0.0001) and response to secretagogue (EP51389; P < 0.03) were lower in mares with high BCS. On January 19, the LH response to GnRH was higher (P < 0.02) in mares with high BCS; the prolactin response to TRH also was higher (P < 0.01) in mares with high BCS. In conclusion, nutrient restriction resulting in low BCS in mares resulted in a profound seasonal anovulatory period that was accompanied by lower leptin, IGF-I, and prolactin concentrations. All but one mare with high BCS continued to cycle throughout the winter or had significant follicular activity on the ovaries. Although leptin concentrations on average are very low in mares with low BCS and higher in well-fed mares, there is a wide variation in concentrations among well-fed mares, indicating that some other factor(s) may determine leptin concentrations under conditions of high BCS.  相似文献   

20.
REASONS FOR PERFORMING STUDY: Previous surveys of reproductive efficiency in British Thoroughbreds included only mares and stallions standing on studfarms in and around Newmarket. The present study was widened to compare Flatrace (FR) (Group A) and National Hunt (NH) (Group B) mares and stallions on studfarms throughout England. OBJECTIVES: To assess the influences of mare type, status and age, and veterinary manipulations on reproductive efficiency parameters. To compare the inherent fertility of stallions, based on singleton and twin pregnancy rates and pregnancy loss rates, in Groups A and B Thoroughbred breeding stock. METHODS: Managers of 24 FR and 9 NH public studfarms were asked to complete a questionnaire for each mated oestrous cycle shown by 2321 Group A and 1052 Group B mares throughout the 2002 mating season. Parameters such as per cycle singleton and twin pregnancy rates, and pregnancy loss rates were noted, and the success of hormone treatments to induce oestrus and ovulation assessed. The number of matings per oestrus and per pregnancy were recorded, together with the incidence and effectiveness of uterine and other veterinary treatments. The inherent fertility of 84 Group A and 43 Group B stallions in the study, as measured by the singleton and twin early pregnancy rates and the pregnancy loss rates recorded in the mares they mated, was also estimated. RESULTS: Per cycle early pregnancy (Days 13-16) was 63.2% for Group A and 65.3% for Group B mares; and 10.3% and 13.1%, respectively, of those pregnancies were twins or triplets. Early, middle and late pregnancy loss rates were 7.2% vs. 8.0% (Days 15-42), 3.6% vs. 6.1% (Days 42-1st October) and 2.7% vs. 2.1% (October-foaling), respectively. Matings per oestrus and per early pregnancy were significantly higher in Group B vs. Group A mares. For stallions that mated > or = 30 mares, overall early pregnancy rates per cycle in mares mated ranged from 30-89% across the 2 groups. CONCLUSIONS: No major differences in reproductive efficiency were identified between FR and NH mares and stallions. Increasing mare age was the single biggest limiting factor to an otherwise high rate of fertility in well-managed English Thoroughbreds. POTENTIAL RELEVANCE: This study identified factors that influence reproductive efficiency in the Thoroughbred.  相似文献   

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