Follicles Of Mares Research Articles

Follicle Selection in Mares as a Model for Illustrating the Many Hormonal and Biochemical Interactions That Drive a Single Physiological Mechanism.

The mechanism for selection of the future dominant or ovulatory follicle in mares involves a relatively abrupt separation in growth rates between the future dominant follicle and several subordinate follicles and is termed diameter deviation. The event is used to illustrate that a coordinated complex of many follicular, hormonal, and biochemical factors interact and interbalance during a single physiological mechanism. For example, a positive effect of follicle stimulating hormone (FSH) on development of all follicles during the growing phase can later involve a positive effect of luteinizing hormone (LH) but apparently only on the future dominant follicle. In turn, the developing and future dominant follicle produces estradiol which at appropriate times and degrees reduces FSH concentrations to accommodate follicle functions at certain levels of FSH. Meanwhile, the estradiol prevents LH from increasing from a useful to an adverse concentration. These interactions enmesh with the production and roles of other factors (e.g., inhibin, insulin-like growth factor) during follicle selection. The wide array of morphological, hormonal, and biochemical activities occur in harmony even when in the same tissue and often at the same time.

Prediction of the ovulation time in estrus mares by different methods

The study aimed to evaluate the prediction of ovulation time by three different methods body temperature, Dramineski estrus detection apparatus, and observation of the mature follicle daily by ultrasonography in mare’s estrus. Sixteen mature cycling mares were used during the breeding season in15 March and15 June of 2021, aged 5-6 years old, at the Nineveh Equestrian club in Mosul city, Iraq. Mares were examined daily by rectal palpation and ultrasound with a 5.5-7 MHz linear-array transducer probe to scan the ovaries and uterus. The mare's follicle diameter and body temperature were recorded daily in the Dramineski estrus detection apparatus to predict ovulation when the data was up to 400 degrees. The result showed that the body temperature was increased significantly from the 1st day to the third day of estrus at P

Dietary mineral and vitamin supplementation improved the reproduction, the haematology, and some circulating biochemical’s of cyclic East-Bulgarian and Arabian mares

This study aimed to investigate the dietary mineral and vitamin supplementation on the hematological, the circulating biochemical parameters, and the reproductive performance of cyclic mares aged 4–12 years old. Purebred Arabian (PAB, n = 8) and East-Bulgarian (EBB, n = 12) breeds were equally divided into treated and control groups. The nutritional supplement was given orally (50 g daily/animal/day) for seven consecutive days and repeated for 4 consecutive months. All mares were examined daily with ultrasound from exhibiting oestrus signs till ovulation. Blood samples were collected with and without anticoagulant before supplementation, on Day 7 and Day 120 for the measurement of ALT, lactate dehydrogenase, bilirubin, calcium, phosphorus, and creatinine and to perform full blood picture. The nutritional supplement decreased lactate dehydrogenase (p < .05) and creatinine (p < .05). Compared to the PAB mares, control mares had one day shorter oestrous cycle length (20.2 ± 2.13 vs 21.0 ± 2.46 days), but the treated EBB mares had two days shorter oestrus cycle (20.00 ± 1.202 vs 22.00 ± 0.93 days). The oestrus phase of the treated mares was shorter (p < .001) than that of the control mares (3.63 ± 0.38 vs 5.50 ± 0.31 days). The diameter of the dominant follicle varied (p < .05) between the two breeds that was 38.25 ± 1.90 and 36.94 ± 1.70 mm for treated and control EBB but was 35.38 ± 1.41 and 34.89 ± 1.35 mm for treated and control PAB. In conclusion, the nutritional supplement had a good effect on the reproductive status, and on the blood parameters (hematological and biochemical) of the mares, but more research is necessary to recommend its use. Highlights The addition of the nutritional supplementation to the mares from the East-Bulgarian breed lead to shorter oestrus. There was a tendency to shorten the sexual cycle (up to 2 days) and increase the size of the dominant follicles in mares receiving the supplement.

Evaluation of vascularization in the walls of preovulatory follicles in mares with endometritis

Endometritis is a major cause of infertility in mares. The aim of this study is to evaluate the preovulatory follicle (POF) vascularization (A mix, A red, A blue), POF diameter, POF wall thickness, and uterine diameters in mares with or without endometritis. Ten healthy mares and 10 mares with endometritis diagnosed by the combination of transrectal palpation, ultrasonographic examination, and cytology brush were enrolled in the study. Data of the groups obtained at 2 days before the ovulation (day −2) were compared with Student’s t-test. Correlations of the parameters were determined by the Pearson correlation test. To the best of our knowledge, this is the first report indicating a lower vascularization of A mix, A red, A blue, and a significantly lower wall thickness in the POFs of the mares with endometritis compared to the healthy ones (p < 0.01, p < 0.05, p = 0.06, and p < 0.001, respectively). Also, a striking and novel inverse correlation between POF wall thickness and uterine diameter (r = −0.785, p < 0.001) and moderate correlations between POF wall thickness and POF vascularizations of A mix and A red (r = 0.436, p = 0.055, and r = 0.427, p = 0.060, respectively) were determined.

Single injection of triptorelin or buserelin acetate in saline solution induces ovulation in mares the same as a single injection of hCG.

The aim of this study was to assess the efficacy of different doses of buserelin acetate and another GnRH agonist, triptorelin acetate, in saline solution in a single subcutaneous injection, to induce ovulation of growing pre-ovulatory follicle in mare and compare it with the classical treatment of a single injection of hCG. The study is split into 3 experiments over different breeding seasons in the same stud with a random distribution of treatment. The first one was to compare the injection of 6mg of buserelin with 1,500IU of hCG; the second one consisted of comparing different doses of buserelin (6mg and 3mg); and the third one compared three different doses of buserelin (3, 2 and 1mg), 0.1mg of triptorelin with 1,500IU of hCG as a control group. The results of all experiments showed the same efficacy between all treatments with mares ovulating between 24 and 48hr after injection: experiment 1: hCG (78% n=41) and buserelin 6mg (90% n=50); experiment 2: buserelin 6mg (78,1% n=192) and buserelin 3mg (78% n=341); and experiment 3: hCG (87% n=106), buserelin 3mg (84,7% n=137), buserelin 2mg (82,7% n=104), buserelin 1mg (87% n=54) and triptorelin 0.1mg (84,7% n=72). In conclusion, this study contributes to erasing the dogma that has been established since 1975 that a single injection in solution without any long-acting excipient of a GnRH agonist cannot induce ovulation in the mare. This study also shows that a injection of 0.1mg of triptorelin in solution is a good alternative for ovulation induction and is comparable to small doses of buserelin acetate in solution (1mg) and 1,500IU of the gold standard trigger hCG, mainly in countries where human formulation of buserelin is not available.

Environmental effects and repeatability of the follicular diameter in mares

ABSTRACT The objective of this study was to evaluate the effect of environment on follicular diameter and repeatability of the size of preovulatory follicles of mares. Temperature, rainfall, and photoperiod were measured, and their effects were evaluated on follicular dynamics. Data were studied by analysis of variance of follicular size and environment traits. During the five years, 7% double ovulations and 159 anovulatory follicles were recorded. Mean preovulatory follicle diameters of left and right ovaries were 39.3±3.8 and 39.2±3.5 mm [...]

Does Clinical Treatment with Phenylbutazone and Meloxicam in the Pre-ovulatory Period Influence the Ovulation Rate in Mares?

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.

321 CYTOSKELETAL ALTERATIONS OF EQUINE OOCYTES THAT FAILED TO CLEAVE AFTER INTRACYTOPLASMIC SPERM INJECTION: EVALUATION OF MATERNAL AND CELL AGING

Intracytoplasmic sperm injection (ICSI) is used for assisted fertilization of equine oocytes. However, not all oocytes cleave after ICSI. Maternal aging deleteriously affects fertility in mares and women, with reduced oocyte quality and success of assisted reproductive technologies. In the oocyte, senescence and cell-programmed death begins after maturation; the extent that maternal age affects these events is unknown. We hypothesised that formation of α/β tubulin asters and f-actin bubbles are associated with aging of the oocyte in vitro and/or aging of the oocyte in vivo, in aged donors. In Exp 1, oocytes were collected from ovaries obtained from an abattoir and matured for 28 h and selected for polar body extrusion (0 h). At 0, 24, and 48 h, oocytes (n = 38 total) were fixed in MTSB-XF and transferred into wash solution with 1% BSA and 0.1% Triton X-100 in PBS for immunostaining. For experiment 2, oocytes were collected from preovulatory follicles of mares (9–25 yr) in a clinical ICSI program and injected with sperm from various stallions after extrusion of a polar body. Between 24 to 51 h after ICSI, uncleaved oocytes (n = 52, single cell without evidence of fragmentation or indentation of the oolemma) were fixed. All oocytes were incubated with α/β tubulin and human-anti-centromere antibody-CREST/ACA (1 : 100 each). Following primary incubation, oocytes were washed and incubated with Alexa 488, Alexa 647, Alexa 561-phalloidin, and Hoechst 33258. Images and Z-stacks were acquired on an Olympus IX81 spinning disk confocal microscope. Morphometric and intensity analyses of images were performed using SlideBook software (Denver, CO). Student's t-test, Fisher's exact test, and chi-square analyses were used for statistical comparisons. After aging in vitro (experiment 1), the number of oocytes with tubulin multiasters increased (P &lt; 0.001; 9% at 0 h, 14% at 24 h, 85% at 48 h); however, actin bubbling was observed in only 5/38 (13%) oocytes, with no effect of incubation time. In experiment 2, tubulin multiasters were present in 62% of oocytes that failed to cleave. More multiasters were observed per oocyte from mares ≤13 yr than ≥20 yr (P = 0.03) and fixed at 24 to 28 h than 44 to 51 h (P = 0.04). Actin bubbles were observed in 71% of oocytes that failed to cleave after ICSI, with more actin bubbles in oocytes from mares ≥20 yr than ≤13 yr (P = 0.01) and fixed 44 to 51 h versus 24 to 28 h after ICSI (P = 0.05). The sum intensity and area of the actin bubbles were higher in oocytes fixed at 44 to 51 h than 24 to 28 h (P = 0.01 and P = 0.04). The area occupied by the actin bubbles was larger (P = 0.05) in oocytes from mares ≥20 yr than ≤13 yr. This study demonstrates actin bubbles and tubulin asters are involved in oocyte aging and cytoskeleton remodelling with or without fertilization. Although actin structures were associated with donor age and hours after ICSI, they were not present in unfertilized oocytes aged in vitro. Multiaster formation was associated with cell senescence in oocytes aged in vitro. Although not previously reported for the equine oocyte, multiaster formation appeared to be an initial fertilization event within the oocyte associated with attempted zygote development.

Influence of l-arginine supplementation on reproductive blood flow and embryo recovery rates in mares

Supplementation with l-arginine can increase uterine arterial blood flow and vascular perfusion of the preovulatory follicle in mares. Increased vascular perfusion of the preovulatory follicle has been correlated with successful pregnancy in mares. The objective of this study was to determine if supplemental l-arginine would increase ovarian arterial blood flow, vascular perfusion of the preovulatory follicle, and embryo recovery rates in mares. Mares were blocked by age and breed and assigned at random within block to l-arginine supplementation or control groups. Mares were fed l-arginine beginning 17 days before and through the duration of the study. Transrectal Doppler ultrasonography was used to measure ovarian arterial blood flow and vascular perfusion of the preovulatory follicle daily when it reached 35 mm and subsequent CL on Days 2, 4, and 6. Mares, on achieving a follicle of 35 mm or more were bred via artificial insemination and an embryo collection was attempted 7 days after ovulation. Treatment did not affect interovulatory interval (arginine-treated, 18.1 ± 2.6 days; control, 20.7 ± 2.3 days) or embryo recovery rate (arginine-treated, 54%; control, 48%). Mares treated with l-arginine had a larger follicle for the 10 days preceding ovulation than control mares (30.4 ± 1.2 and 26.3 ± 1.3 mm, respectively; P < 0.05) and vascular perfusion of the dominant follicle tended (P = 0.10) to be greater for the 4 days before ovulation. No differences were observed between groups in diameter or vascular perfusion of the CL. Resistance indices, normalized to ovulation, were not significantly different between groups during the follicular or luteal phase. Oral l-arginine supplementation increased the size and tended to increase perfusion of the follicle 1, but had no effect on luteal perfusion or embryo recovery rates in mares.

Evaluation of growth models for follicle development and ovulation in Lusitano mares

Several growth models are commonly used in the biological sciences, to model the follicle growth occurring in the estrous cycle. The aim of this project was to find the model that best fit the follicular size growth data for Lusitano mares. Retrospective data collected from reproduction book records of n=84 mares and n=124 cycles was used to find the series to be fitted to the models. The exponential, Gompertz, logistic, von Bertalanffy, Richards and Weibull models were used, and the most parsimonious and best fit was achieved with the logistic model (r2=0.999). The logistic model fits the Lusitano mare's follicle size growth data very well and its parameters were also shown to have a credible biological interpretation.

Short-term feed restriction decreases the systemic and intrafollicular concentrations of leptin and increases the vascularity of the preovulatory follicle in mares

The objective of this study was to evaluate the effect of short-term feed restriction on characteristics of the preovulatory follicle and on concentrations of systemic hormones (leptin, follicle-stimulating hormone [FSH], luteinizing hormone [LH]) and follicular fluid hormones and growth factors (leptin, estradiol, inhibin-A, activin-A, free insulin-like growth factor-1 [IGF1], insulin-like growth factor binding protein 2 [IGFBP2], vascular endothelial growth factor [VEGF]). Mares were submitted to a short-term (48 h) feed restriction when the expected ovulatory follicle was ≥27mm (Hour 0) or served as controls (n=8/group). No effect of short-term feed restriction was detected for systemic concentrations of FSH and LH and for intrafollicular concentrations of estradiol, activin-A, free IGF1, and IGFBP2. Restricted mares had decreased systemic concentrations of leptin at Hour 24 (approached significance) and at Hours 36 and 48 (P<0.04). Follicular fluid of restricted mares at Hour 48 had lower (P<0.02) concentration of leptin and a tendency (P<0.1) for greater concentrations of inhibin-A and VEGF. The percentage of wall of the preovulatory follicle with color-Doppler signals of blood flow at Hour 48 was greater (P<0.04) in the restricted group. Intrafollicular concentration of leptin (combined groups) was positively correlated with score for body condition (r=+0.60; P<0.002) and negatively correlated with the percentage of the follicle wall with blood-flow signals (r=−0.60; P<0.02). Our favored interpretation is that the preovulatory follicle seems to compensate for a nutritional deficiency by increasing the blood flow in the follicle wall.

Positive effect of FSH but not LH on early development of the dominant follicle in mares

The effects of FSH, LH or both on follicular growth and intrafollicular free insulin-like growth factor (IGF)-1 and oestradiol were investigated in mares after the beginning of deviation (largest follicle >/= 20 mm; Hour 0). A single treatment with a gonadotropin-releasing hormone antagonist (acyline) was given at Hour 3 to suppress the concentrations of FSH and LH. Five groups (n = 5 mares per group) were evaluated in the present study: (1) control; (2) acyline treated; (3) acyline + recombinant equine (re) FSH treated; (4) acyline + reLH treated; and (5) combined acyline + reFSH + reLH treated. Beginning at Hour 3, reFSH and reLH were given at 6-h intervals in eight decreasing or increasing doses, respectively. The reFSH and reLH prevented the acyline-induced decreases in FSH and LH, respectively. Diameters and concentrations of intrafollicular free IGF-1 and oestradiol of the two largest follicles at Hour 48 did not differ significantly between the control and acyline + FSH groups, but were reduced (P < 0.05) similarly in the acyline and acyline + LH groups. The combination of reFSH and reLH was no more effective than reFSH alone. The results demonstrate a role for FSH but not LH in the growth of the largest follicle and intrafollicular concentrations of free IGF-1 and oestradiol during the 48 h after the beginning of deviation in mares.

Functional relationships among intrafollicular insulin-like growth factor 1, circulatory gonadotropins, and development of the dominant follicle in mares

The functional relationships among intrafollicular free insulin-like growth factor 1 (IGF1), circulatory gonadotropins, and development of the dominant follicle were studied in 40 mares in two experiments. A GnRH antagonist (Acyline) was given i.m. at the expected beginning of follicular deviation (largest follicle or F1 ≥ 20 mm; Day 0) alone (Acyline group) or in combination with intrafollicular treatment of F1 with rhIGF1 (Acyline/IGF1 group). In Experiment 1, blood samples, follicular-fluid samples, and diameter of F1 were taken on Days 1 and 2. In Experiment 2, daily follicular diameter and blood samples were taken from Day 0 to ovulation. The GnRH antagonist induced a 50% decrease in circulatory FSH concentrations for 1 d and in LH for 2 d. In Experiment 1, control and Acyline/IGF1 groups had greater intrafollicular free IGF1 ( P < 0.05) and inhibin-A concentrations ( P < 0.08) than the Acyline group. The intrafollicular concentration of estradiol on Day 2 was greater ( P < 0.05) in the control group than in the Acyline and the Acyline/IGF1 groups. In Experiment 2, a decrease in diameter of F1 in the Acyline group was followed by a new follicular wave. All IGF-treated follicles grew and ovulated. Results indicated that the increase in intrafollicular free IGF1 observed in F1 in association with deviation is gonadotropin dependent. During the period of lesser gonadotropin concentrations from Acyline treatment, intrafollicular IGF1 stimulated follicular growth and inhibin concentrations, but not intrafollicular estradiol production.

Follicle Deviation in Ovulatory Follicular Waves with One or Two Dominant Follicles in Mares

The follicle and hormone aspects of diameter deviation and development of one dominant (>/=28 mm) follicle (1DF) vs two dominant follicles (2DF) were studied in 32 ovulatory follicular waves in mares. Follicles were ranked each day as F1 (largest) to F3. The beginning of deviation was designated day 0 and preceded the first increase in the differences in diameter between F1 and F2 in the 1DF group and between a combination of F1 and F2 vs F3 in the 2DF group. One dominant follicle and 2DF developed in 21 (66%) and 11 (34%) waves, respectively. Double ovulations occurred in only one of the waves with 2DF. In 8/11 waves with 2DF, a second deviation occurred between F1 and F2 on 2.5 +/- 0.4 days after the first deviation. On day 0, 1DF and 2DF waves were similar in number of days after ovulation, number of follicles, difference in diameter between F1 and F2, and plasma concentrations of LH, estradiol and immunoreactive inhibin. The interval from maximum FSH concentration to day 0 was longer (p < 0.05) and FSH concentration was lower (p < 0.05) on days -1 to 4 in the 2DF group. The similarities on day 0 in the characteristics of 1DF and 2DF waves despite the differences in the declining portions of the FSH profile indicated that a specific day of the FSH decline or a specific concentration were not factors in initiating deviation. Unlike reported results in heifers, the results in mares did not indicate a hormonal basis for the development of 2DF or two deviations.

The efficacy of recombinant equine follicle stimulating hormone (reFSH) to promote follicular growth in mares using a follicular suppression model

The efficacy of a recently engineered single chain recombinant equine follicle stimulating hormone (reFSH) was investigated in estrous cycling mares whose gonadotropins and follicular activity had been suppressed by concurrent treatment with progesterone and estradiol (P&E). Time of estrus was synchronized in 15 estrous cycling mares during the breeding season with prostaglandins F 2α (PGF 2α). The day after ovulation, mares were treated once daily with P&E for 14 days. Mares received a second injection of PGF 2α on day 6 of the synchronized estrous cycle to induce luteolysis. On day 8 post-ovulation mares were randomly assigned to three groups: small dose reFSH-treatment group (0.5 mg reFSH IV, twice daily); large dose reFSH-treatment group (0.85 mg reFSH IV twice daily); control group (saline IV, twice daily). reFSH treatment occurred concurrently with the last week of P&E treatment. After a follicle or cohort of follicles reached 35 mm in diameter, mares were injected with 0.75 mg of recombinant equine luteinizing hormone (reLH) to induce ovulation. Post-treatment ovulation was assessed. Daily blood samples were collected for analysis of FSH, LH, estradiol, progesterone, and inhibin by radioimmunoassay (RIA). On the first day of reFSH/saline treatment, blood samples were collected periodically from 1 h prior to treatment to 6 h post-injection via an indwelling jugular catheter to determine acute changes in FSH concentrations. Monitoring of follicular activity, estrus, and ovulation was performed daily by utilizing a stallion and transrectal ultrasonography. A difference ( p ≤ 0.05) between the largest diameter follicle in the reFSH-treatment groups compared to controls occurred on day 14 post-ovulation, the day treatments ended, and the difference continued until day 21 post-ovulation. reFSH-treatment groups had larger ( p ≤ 0.05) numbers of 20–29 mm follicles (days 13–18), 30–34 mm follicles (days 15–20) and ≥35 mm follicles (days 16–21) than controls. Mares treated with reFSH, at either dose, took less time (average: 2.95 ± 0.42 days) to develop 2–3 times more pre-ovulatory follicles than control mares (7.8 ± 0.51 days) ( p ≤ 0.05). The number of ovulations between treated mares and controls were similar due to a greater incidence of ovulation failure in reFSH-treated mares. During reFSH treatment, concentrations of plasma FSH, inhibin and estradiol were greater ( p ≤ 0.05) compared to control concentrations. Plasma LH concentrations in reFSH-treated mares were suppressed and did not exhibit the ovulatory surge of controls ( p ≤ 0.05). Plasma progesterone concentrations were not different across groups. These findings demonstrate the specific effects of reFSH to increase number of total follicles including pre-ovulatory follicles in mares with endogenous pituitary gonadotropins and follicular growth suppressed by a regimen of P&E.

Induction of haemorrhagic anovulatory follicles in mares

A follicular wave and luteolysis were induced in mares by ablation of follicles > or =6 mm and treatment with prostaglandin F(2alpha) (PGF) on Day 10 (where ovulation = Day 0). The incidence of haemorrhagic anovulatory follicles (HAFs) in the induced waves (20%) was greater (P < 0.007) than in preceding spontaneous waves (2%). Hormone and follicle dynamics were compared between induced follicular waves that ended in ovulations (ovulating group; n = 36) v. HAFs (HAF group; n = 9). The day of the first ovulation or the beginning of HAF formation at the end of an induced wave was designated as post-treatment Day 0. The mean 13-day interval from Day 10 (PGF and ablation) to the post-treatment ovulation was normalised into Days 10 to 16, followed by Day -6 to Day 0 relative to the post-treatment ovulation. Concentrations of LH were greater (P < 0.05) in the HAF group than in the ovulating group on Days 10, 11, 12, 14, -3 and -2. The HAF group had greater (P < 0.003) LH concentrations on Day 10 of the preceding oestrous cycle with spontaneous ovulatory waves. The diameter of the largest follicle was less (P < 0.05) in the HAF group on most days between Day 13 and Day -1 and this was attributable to later (P < 0.002) emergence of the future largest follicle at 6 mm in the HAF group (Day 12.4 +/- 0.5) than in the ovulating group (Day 11.3 +/- 0.1). The results indicate that the high incidence of HAFs after PGF and ablation was associated with later follicle emergence and immediate and continuing greater LH concentration after PGF treatment, apparently augmented by an inherently high pretreatment LH concentration.

Relationships of Follicle Versus Oocyte Maturity to Ultrasound Morphology, Blood Flow, and Hormone Concentrations of the Preovulatory Follicle in Mares1

The effects of ultrasound morphology, vascularity, and follicular-fluid hormones of the preovulatory follicle on oocyte recovery rate and on follicle and oocyte maturity rates were studied for 60 spontaneous and solitary preovulatory follicles in mares. An ovulation-inducing dose of hCG was given when the follicle was >or=32 mm (Hour 0), and a procedure for oocyte recovery was done 30 h later (Hour 30). Between Hours 0 and 30, diameter of the follicle increased less and circulating estradiol (E2) concentrations decreased more in groups with successful versus nonsuccessful oocyte recovery and in groups with mature versus immature recovered oocytes, as indicated by significant interactions of group and hour. Significant differences in blood-flow end points between groups were not detected. At Hour 30, the frequency of granulosa serration, an indicator of impending ovulation, was higher (P < 0.001), and the number and expansion of granulosa cells in the lavaging fluid, indicators of follicle maturity, were greater in the oocyte-recovery group and in the oocyte-mature group. Follicular-fluid concentrations of E2, progesterone, and free insulin-like growth factor (IGF) 1 were not different between the oocyte-recovery and -nonrecovery groups. Concentration of progesterone was significantly greater, and E2 and free IGF1 were less in the oocyte-mature than in the immature groups. Results indicated that the post-hCG oocyte-recovery and oocyte-maturity rates were positively affected by follicle maturity. Greater follicular-fluid progesterone and lower E2 and free IGF concentrations were associated temporally with maturation of the oocyte but not with maturation of the follicle.

Incidence, Endocrinology, Vascularity, and Morphology of Hemorrhagic Anovulatory Follicles in Mares

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.

CORELATIONS BETWEEN THE BODY TEMPERATURE FLUCTUATION AND THE PREDICTION OF OVULATION IN MARES

Due to the difficulties involved in the prediction of ovulation in mares, which ovulate before the end of estrus, a more efficient, less invasive method that could reduce the need for repeated teasing and ultrasonography is needed. It is possible that the conventional methods (palpation, ultrasonography, teasing) currently used are the most effective when predicting ovulation in the mare. The evaluation of the body temperature curve (temperature fluctuations) in the study of the prediction of ovulation is used successfully for humans and there are also some articles about it for dairy cattle and rats. The current study is presenting some observations about the fluctuation of body temperature around the moment of ovulation in mares. The current study utilized four mature cycling Romanian Sport Horse mares, and was conducted from July-August 2007. Observations were recorded from the first day mares exhibited signs of behavioral estrus through day three after the end of the estrus once daily. Beginning with the moment when an ovulatory follicle (>35mm) was detected using ultrasonography the mare's follicle size and temperature were recorded approximately every six hours until ovulation. All four mares were palpated every other day during estrus to determine the presence of an ovulatory follicle (>35mm). Ovulation was established through palpation by the presence of an ovulation depression or corpus hemorrhagicum on the ovary hosting the ovulatory follicle. The rectal temperatures were recorded using a veterinary digital thermometer four times daily . Differences in the fluctuation of the rectal temperature were found in relation to the presence of an ovulatory follicle of greater than 35mm compared with the absence of it (plus 0.1 OC -0.5 OC), but there were no changes 24 hr prior to ovulation that could be used to predict ovulation ( a mean of 37.7 OC pre-ovulation and post-ovulation).

Relationships of changes in B-mode echotexture and colour-Doppler signals in the wall of the preovulatory follicle to changes in systemic oestradiol concentrations and the effects of human chorionic gonadotrophin in mares

A duplex grey-scale and colour-Doppler ultrasound instrument was used to study the changes in the wall of the preovulatory follicle in mares. When the follicle reached > or =35 mm (hour 0), mares were randomized into control (n = 16) and human chorionic gonadotropin (hCG)-treated (n = 16) groups. The hCG treatment was given at hour 0. Scanning was done every 12 h until hour 36, every hour between hours 36 and 48, and every 12 h thereafter until ovulation. Blood was sampled every 12 h for oestradiol assay. During the period 0-24 h post-treatment, oestradiol concentrations decreased in the hCG group and increased in the controls (significant interaction). During the period 0-36 h post-treatment, thickness and echogenicity of the granulosa increased in the hCG group but not in the controls. During the period 36 to 12 h before ovulation, granulosa and colour-Doppler end-points increased in the control and hCG groups (hour effects), while oestradiol was decreasing in both groups. The prominence and percentage of follicle circumference with an anechoic band peripheral to the granulosa and colour-Doppler signals in the follicle wall, indicating arterial blood flow, decreased during the period 4 to 1 h before ovulation (hour effects). Results indicated that the ultrasonographic changes of the wall of the preovulatory follicle were not associated temporally with changes in oestradiol concentrations and prominence of an anechoic band, and colour-Doppler signals decreased during the few hours before ovulation. The hypothesis that the latter portion of the ovulatory LH surge has a negative effect on systemic oestradiol was supported by the immediate decrease in oestradiol concentrations when hCG was injected.