Hemorrhagic ovarian follicles in llamas

The ovaries of 74 llamas were examined daily by transrectal ultrasonography for at least 30 d. Hemorrhagic follicles were observed in 13 (18%) llamas (incidence per anovulatory dominant follicle, 16%). The proportion of llamas in which a hemorrhagic follicle was detected was different among groups (nonmated, 8 25 ; mated to a vasectomized male, 4 21 ; mated to an intact male, nonpregnant, 1 10 ; mated to an intact male, pregnant, 0 18 ; P<0.05). A hemorrhagic follicle, observed grossly after ovariectomy, was large (13 mm) and fluctuant, with a thin translucent wall and dark red contents. No ovulatory stigma was detected, and after incising the wall, bloody fluid escaped and the follicle collapsed leaving only a small blood clot within the antrum. Ultrasonically, the formation of a hemorrhagic follicle was indicated by scattered free-floating echogenic spots within the follicular antrum which swirled upon ballottement of the ovary. The antral contents appeared to become organized (did not swirl when ballotted) after follicle growth ceased. Ultrasonic indications of antral hemorrhage were not observed in any follicles in which ovulation was later detected (0 45 ovulatory follicles). All of the hemorrhagic follicles (13 13 ) involved the dominant follicle of a wave during which no copulatory stimulus was applied. Hemorrhagic follicles were apparently anovulatory and were repeatable (P<0.05) within individuals. The interval from first detection to the first day of maximum diameter was longer (P<0.05) and maximum diameter was greater (P<0.0001) for hemorrhagic follicles than nonhemorrhagic follicles (16.4 versus 13.1 d and 22.1 versus 12.8 mm, respectively); however, the interwave interval was not affected by the presence of a hemorrhagic follicle. Luteinization of the hemorrhagic follicle was indicated (thickened wall) in two llamas by an elevated plasma progesterone concentration and/or by ultrasound. By their large size, hemorrhagic follicles may be interpreted as hemorrhagic follicular cysts; however, they were not associated with other ovarian irregularities or with infertility.     

Folliculogenesis during the transitional period and early ovulatory season in mares

Individual follicles were monitored by ultrasonography in 15 mares during the transitional period preceding the first ovulation of the year and in 9 mares during the first interovulatory interval. During the transitional period, 7 mares developed 1-3 anovulatory follicular waves characterized by a dominant follicle (maximum diameter greater than or equal to 38 mm) that had growing, static, and regressing phases. The emergence of a subsequent wave (anovulatory or ovulatory) did not occur until the dominant follicle of the previous wave was in the static phase. After the emergence of the subsequent wave, the previous dominant follicle regressed. The mean (+/- s.d.) length of the interval between successive waves was 10.8 +/- 2.2 days. Before the emergence of waves (identified by a dominant follicle), follicular activity seemed erratic and follicles did not reach greater than 35 mm. During the interovulatory interval, 6 mares developed 2 waves (an anovulatory wave and a subsequent ovulatory wave) and 3 mares developed only 1 detected wave (the ovulatory wave). The ovulatory follicle at the end of the transitional period reached 20 mm earlier (Day - 15), grew slower (2.6 +/- 0.1 mm/day; mean +/- s.e.m.) but reached a larger diameter on Day - 1 (50.5 +/- 1.1 mm) than for the ovulatory follicle at the end of the interovulatory interval (Day - 10, 3.6 +/- 0.2 mm/day, 44.4 +/- 1.0 mm, respectively; P less than 0.05 for each end point). The interval from cessation of growth of the largest subordinate follicle to the occurrence of ovulation was longer (P less than 0.05) for end of the transitional period (9.5 +/- 0.7 days) than for the end of the interovulatory interval (6.8 +/- 0.6 days). Results demonstrated the occurrence of rhythmic follicular waves during some transitional periods and the occurrence of 2 waves during some of the first oestrous cycles of the year.     

Estrogen concentrations in milk at estrus and ovulation in dairy cows

The aim of the present study was two-fold. First, to characterize the secretory profiles of oestradiol-17beta and progesterone in relation to the structural changes observed by ultrasonography during follicular dynamics in non-ovulating llamas. Second, to evaluate the effect of exogenous progesterone on follicular activity, in terms of follicle development and hormone production. In experiment one, six adult non-pregnant, non-lactating llamas were examined daily by rectal palpation and transrectal ultrasonography during 70 days. On day 54, intravaginal devices containing 0.33 g of progesterone (CIDR) were inserted and left in the vagina during 16 days. The mean duration of a follicular wave was 22.6+/-2.5 days. The follicular growth phase (follicles growing from 3mm to maximum size) averaged 9.2+/-2.8 days, the mature phase (follicles around maximum size) 5.2+/-1.4 days and regression phase (follicles with decreasing size) 8.2+/-2.2 days. Oestradiol-17beta plasma concentrations exhibited a similar wave pattern (P<0.05). In addition, oestradiol-17beta peak plasma concentrations (46.9+/-3.3 pmoll(-1)) were attained approximately 12 days after the beginning of the growing phase in connection with maximum follicle size (11.8+/-1.6mm). After CIDR insertion, a rapid increase in plasma progesterone concentrations was observed, with peak concentrations attained on day 1 after insertion. Thereafter, concentrations decreased gradually. Mean follicle size steadily decreased from the day of CIDR insertion to day 11 post-insertion (10.3+/-1.6 and 3.3+/-0.8mm, respectively). In order to investigate the effect of follicle size at CIDR insertion on the outcome of progesterone treatment, experiment two was designed. Sixteen adult non-pregnant and non-lactating llamas were divided into four groups according to follicle development at the time of CIDR insertion (group I: follicles < or =6 mm; group II: follicles between 6 and 9 mm; group III: follicles between 10 and 14 mm and group IV, regressing follicles). In groups II, III and IV, a significant decrease in follicle size was observed after the insertion of the CIDR device. In group I, no further development of dominant follicles was observed until the device was withdrawn. In all cases, the smallest diameter was registered between days 5 and 7 after the beginning of treatment. In conclusion, a detailed characterization of follicular waves using ultrasound and hormone determinations simultaneously in non-ovulating llamas and after the insertion of progesterone releasing devices, is presented.     

Ovarian follicular and luteal dynamics in wapiti during seasonal transitions

Transitions from the anovulatory to the ovulatory season (n=20) and ovulatory to anovulatory season (n=11), were monitored daily by transrectal ultrasonography in wapiti. In 17 of 20 observations, the first interovulatory interval (IOI) was short (9.1+/-0.3 days; mean+/-S.E.M.) compared with later in the ovulatory season (21.3+/-0.1) and the last IOI (21.2+/-0.6 days). With one exception, the short IOI were composed of only one wave of follicular development. Subsequent IOI were composed of two or three waves. Maximum diameters of the first two ovulatory follicles were similar (11.3+/-0.4 mm versus 11.3+/-0.2 mm), but both were larger (P<0.05) than the last two ovulatory follicles of the ovulatory season (10.3+/-0.3 and 10.1+/-0.4 mm). Multiple ovulations occurred in three hinds at the first ovulation of the season and in one hind at the second ovulation, but were not at any other time. Day-to-day profiles of CL diameter and plasma progesterone concentration were smaller (P<0.05) for short versus long IOI. Maximum diameter (12.8+/-0.6 mm versus 12.5+/-0.6 mm) and the diameter profile of the last CL of the season were not different from that of the previous CL. In summary, transition to regular ovulation occurred over a 3-week interval and was preceded by one short IOI (9 days). Multiple ovulations were detected only at the onset of the ovulatory season. The characteristics of the last IOI of the ovulatory season were similar to those reported during the rut. The wave pattern of follicle development was maintained throughout both fall and winter transition periods and follicular wave emergence was preceded by a surge in serum FSH concentrations. Transition to anovulation occurred over a 3-month interval and was marked by a failure of the dominant follicle to ovulate after a typical luteal phase.     

Developmental pattern of small antral follicles in the bovine ovary

The study was designed to characterize the developmental pattern of 1- to 3-mm follicles and to determine the stage at which the future dominant follicle first attains a size advantage among its cohorts. In experiment 1, heifers (n = 18) were examined every 24 h by transrectal ultrasonography for one interovulatory interval (IOI). In experiment 2, cows (n = 9) were examined every 6 h from 5 to 13 days after ovulation to monitor precisely the diameter changes of individual follicles >/=1 mm during emergence of wave 2. Results revealed a change over days (P < 0.05) in the number of 1- to 3-mm follicles, with a maximum (P < 0.05) 1 or 2 days before wave emergence (conventionally defined as the time when the dominant follicle is first detected at 4 mm), followed 3-4 days later by a maximum (P < 0.05) in the number of >/=4-mm follicles. The profiles of small (1-3 mm) and large (>/=4-mm) follicles were inversely proportional (r = -0.79; P = 0.01). The profile of the number of 1- to 3-mm follicles during wave emergence was similar (P = 0.63) between waves in two-wave IOI, but differed (P < 0.01) among waves in three-wave IOI as a result of a greater number of follicles in the ovulatory wave (P < 0.04). As well, the number of follicles in the ovulatory wave tended to be greater (P < 0.06) in three-wave IOI than in two-wave IOI. The future dominant follicle was first identified at a diameter of 1 mm and emerged 6-12 h earlier than the first subordinate follicle (P < 0.01). After detection of the dominant follicle at 1 mm (0 h), its diameter differed from that of the first and second subordinate follicles at 24 h (P = 0.04) and 12 h (P = 0.01), when the dominant follicle was 2.4 +/- 0.17 mm and 1.7 +/- 0.14 mm, respectively. The growth rate of the dominant follicle differed from that of the first and second subordinate follicles at 120 h (P = 0.03) and 108 h (P = 0.02), when the dominant follicle was 9.5 +/- 0.30 mm and 8.8 +/- 0.49 mm, respectively. Emergence of the future dominant (r = 0.71), first (r = 0.73), and second (r = 0.76) subordinate follicles was temporally associated (P < 0.01) with a rise in circulating concentrations of FSH. Transient, nocturnal elevations in plasma FSH concentration were followed within 6 h by an increase in the growth rate of 1- to 3-mm follicles. We conclude that 1) 1- to 3-mm follicles develop in a wave-like manner in association with surges in plasma concentrations of FSH, 2) 1- to 3-mm follicles are exquisitely responsive to transient elevations in FSH, and 3) selection of the dominant follicle is manifest earlier than previously documented and is characterized by a hierarchical progression over a period encompassing the entire FSH surge (5 days).     

Comparison of the effect of natural mating, LH, and GnRH on interval to ovulation and luteal function in llamas

Gonadotropins and GnRH have been used to electively induce ovulation in llamas and alpacas, but critical evaluation of the natural interval to ovulation after mating has not been performed nor has a direct comparison of the effects of natural mating versus hormone treatments on this interval and subsequent luteal development. The objectives of this study were to compare the effects of hormonal treatments and natural mating on ovulation induction, interval to ovulation, and luteal development in llamas. The ovaries of llamas were examined by transrectal ultrasonography once daily. Llamas with a large follicle were assigned randomly to be: (1) mated with an intact male (mated; n=10); (2) given 5 mg of LH im (LH; n=11); or (3) 50 microg of GnRH im (GnRH; n=10). Ultrasound examinations were performed every 4h from treatment (day 0) to ovulation and thereafter once daily for 15 consecutive days to monitor CL growth and regression (n=5 per group). Plasma progesterone concentrations were measured at days 0, 3, 6, 9, and 12 after treatment to evaluate CL function. The size of the largest preovulatory follicle at the time of treatment did not differ among groups (11+/-0.6, 10.5+/-0.8, 11.8+/-0.9 mm, for mated, LH, and GnRH groups, respectively; P=0.6). No differences were detected among groups (mated, LH, and GnRH) in ovulation rate (80%, 91%, 80%, respectively; P=0.6), or interval from treatment to ovulation (30.0+/-0.5, 29.3+/-0.6, 29.3+/-0.7h, respectively; P=0.9). Similarly, no differences were detected among groups (mated, LH, and GnRH) in maximum CL diameter (14.2+/-0.3, 13.2+/-0.5, and 13.0+/-0.7 mm, respectively; P=0.5), the day of maximum CL diameter (7.6+/-0.2, 7.6+/-0.2, and 7.4+/-0.4 mm, respectively; P=0.6), or the day on which the CL began to regress (12.3+/-0.3 [non-pregnant, n=3], 11.8+/-0.6, 12.2+/-0.4, respectively; P=0.4). The diameter of the CL and plasma progesterone concentrations changed over days (P<0.0001) but the profiles did not differ among groups. In summary, ovulation rate, interval to ovulation, and luteal development were similar among llamas that were mated naturally or treated with LH or GnRH. We conclude that both hormonal preparations are equally reliable for inducing ovulation and suitable for synchronization for artificial insemination or embryo transfer program.     

Aberrant blood flow area and plasma gonadotropin concentrations during the development of dominant-sized transitional anovulatory follicles in mares

Color Doppler transrectal ultrasound was used to evaluate blood flow area in the wall of dominant anovulatory follicles versus ovulatory follicles in mares during the transition between anovulatory and ovulatory seasons. Daily examinations were done in 11 control mares toward the end of the anovulatory season. In 13 separate mares, follicular fluid was collected from 30-mm follicles, and blood flow areas from control mares were used as a basis for designating the sampled follicle as either anovulatory or ovulatory. Blood flow area in the controls ranged from 0.18 to 0.35 cm(2) in six mares on the day of a 30-mm anovulatory follicle and from 0.25 to 0.86 cm(2) in 11 mares on the day of a 30-mm ovulatory follicle; the ranges did not overlap except for one follicle. In the controls, mean blood flow area was lower (P < 0.05) in the anovulatory group than in the ovulatory group for each day beginning with the first Doppler examination at 25 mm. For plasma LH in controls, an effect of follicle group (P < 0.0001) and an interaction (P < 0.0001) of group by day reflected lower (P < 0.05) concentrations in the anovulatory group on Days -6, -2, and 5-8 (Day 0 = 30-mm follicle). For plasma FSH, an interaction (P < 0.0001) reflected higher (P < 0.05) concentrations in the anovulatory group on Days -3 and 1-4. More (P < 0.05) statistically identified FSH surges occurred in the anovulatory group during Days -7 to 8. In the sampled mares, follicular-fluid concentrations of estradiol, free insulin-like growth factor-1, inhibin-A, and vascular endothelial growth factor were lower (P < 0.05) in 30-mm designated anovulatory follicles than in 30-mm designated ovulatory follicles. Results were interpreted as follows: 1) The future anovulatory dominant-sized follicle developed under an LH deficiency, 2) the LH deficiency led to reductions in blood flow area and in concentrations of follicular-fluid factors, and 3) the reduction in follicle production of FSH suppressors resulted in higher plasma FSH concentrations.     

Effect of progesterone on ovarian follicles, emergence of follicular waves and circulating follicle-stimulating hormone in heifers.

The hypothesis was tested that greater growth of the dominant follicle of wave 1 (first follicular wave of an interovulatory interval), compared with that of subsequent anovulatory waves, is due to lower circulating concentrations of progesterone during the growing phase of the follicle. Control heifers (n = 6) were compared with heifers (n = 6) treated with a decreasing dose of progesterone from day 0 to day 5 (ovulation = day 0). Maximum diameter (12.7 +/- 0.9 versus 15.3 +/- 0.7 mm) and mean diameter of the dominant follicle of wave 1, averaged over days, were smaller (P < 0.05) in the progesterone-treated than in the control group. Progesterone treatment did not suppress circulating follicle-stimulating hormone (FSH); but the second FSH surge was earlier, resulting in earlier emergence of wave 2 as indicated by a tendency (P < or = 0.1) for group x day interactions attributed to earlier detection of the dominant follicle and an earlier rise in the total number of follicles detected. The stated hypothesis was supported. We also tested the hypothesis that exposure to low circulating concentrations of progesterone at the end of the growing phase of the anovulatory dominant follicle of wave 1 results in continued growth and prolonged maintenance of the dominant follicle. Heifers (n = 6 per group) were given a luteolytic dose of prostaglandin F2 alpha (PGF2 alpha) on day 6 and treated with a low (30 mg day-1), physiological (150 mg day-1), or high (300 mg day-1) dose of progesterone on days 6 to 20. Continued periodic emergence of anovulatory follicular waves occurred (2.1 +/- 0.0 waves, 2.8 +/- 0.2 waves, 3.8 +/- 0.3 waves, respectively; P < 0.05) until treatment was stopped (interovulatory intervals: 26.2 +/- 1.0, 30.8 +/- 0.6 and 40.3 +/- 1.7 days, respectively; P < 0.05). Compared with the physiological dose group, the growth of the dominant follicle was inhibited to a lesser degree in the low-dose group since it grew for longer (P < 0.05) and to a larger diameter (P < 0.05), and persisted for longer (P < 0.05). Prolonged dominance of this oversized (> 20 mm) follicle was associated with delayed emergence of wave 2. The hypothesis was supported. Results also showed that the high dose of progesterone suppressed the dominant follicle more than the physiological dose when given during the growing phase, but not when given after the growing phase.(ABSTRACT TRUNCATED AT 400 WORDS)     

Pattern of follicular growth and resumption of ovarian activity in post-partum beef suckler cows

The ovaries of 18 post-partum beef suckler cows were examined daily, using ultrasound, from Day 5 post partum until a normal oestrous cycle was completed. Periods of growth and regression of medium-sized (5-9 mm) follicles were identified before one medium follicle became dominant (single large follicle greater than or equal to 10 mm). The mean (+/- s.e.m.) number of days from parturition to detection of the first post-partum dominant follicle was 10.2 +/- 0.5. The first post-partum dominant follicle ovulated in 2/18 (11%) cows. The interval from calving to first ovulation (mean +/- s.e.m. = 35.9 +/- 3.3 days) was characterized by the growth and regression of a variable number (mean = 3.2 +/- 0.2; range 1-6) of dominant follicles. The maximum diameter of the dominant follicle increased as the cows approached first ovulation (P less than 0.05). Behavioural oestrus was not detected in 16/18 (89%) cows at first ovulation. Following first ovulation, the length of the subsequent cycle was short (mean = 9.7 +/- 0.5 days; range 8-15 days) in 14/18 (78%) cows and was characterized by the development and ovulation of a single dominant follicle. During oestrous cycles of normal length (mean = 20.6 +/- 0.5 days; range 18-23 days) one (N = 2), two (N = 7) or three (N = 8) dominant follicles were identified. The growth rate, maximum diameter or persistence of non-ovulatory dominant follicles before first ovulation or during oestrous cycles were not different (P greater than 0.05). These data show that, in beef suckler cows, follicular development and formation of a dominant follicle occur early after parturition and the incidence of ovulation of the first dominant follicle is low. The number of dominant follicles that develop before first ovulation is variable; first ovulation is rarely associated with oestrus and short cycles are common after first ovulation. It is concluded that prolonged anoestrus in post-partum beef suckler cows is due to lack of ovulation of a dominant follicle rather than delayed development of dominant follicles.     

Ovarian follicular development in Holstein cows following synchronisation of oestrus with oestradiol benzoate and an intravaginal progesterone releasing insert for 5-9 days and duration of the oestrous cycle and concentrations of progesterone following ovulation

The aim of this study was to determine if the duration of treatment with an intravaginal progesterone releasing insert (IVP(4)) after treatment with oestradiol benzoate (ODB) at the time of insertion and 24 h after removal would affect selected variables including: size of ovarian follicles at the time of removal of inserts, diameter of ovulatory follicles, plasma concentrations of progesterone following ovulation, and duration of the following oestrous cycle. Characteristics of oestrus at a synchronised and spontaneous oestrus were also monitored. Non-lactating Holstein cows were synchronised with an IVP(4) for 5 (n = 10), 7 (n = 10), 8 (n = 9) or 9 (n = 9) days together with injections of ODB at device insertion (2 mg) and 24 h after removal (1 mg). Ultrasonography showed no significant effect of treatment on the day of emergence of preovulatory follicles relative to the day of removal of inserts (overall mean = -4.22 +/- 0.58; P = 0.15) for cows that ovulated within 120 h insert removal (n = 36). Treatment with ODB and an IVP(4) for 5 days reduced the diameter of preovulatory follicles at the time of removal of inserts and for the following 2 days compared to cows treated for 7-9 days (mean difference 2.56 +/- 1.15 mm; P = 0.033) but did not reduce the diameter of the ovulatory follicle (P = 0.21). Day of emergence relative to removal of inserts was associated with the diameter of the ovulatory follicle (R2 = 0.69; P < 0.001). Concentrations of progesterone and the diameter of the corpus luteum following ovulation were not affected by treatment (P > 0.20), but were affected by the diameter of the ovulatory follicle (P < 0.01). Diameter of the ovulatory follicle did not affect interoestrous and interovulatory intervals (P > 0.40). We conclude that treatment with an IVP(4) for 5 compared to 7-9 days with ODB administered at device insertion, and 24 h after removal reduced the diameter of preovulatory follicles at the time of removal of the insert but did not reduce the diameter of the ovulatory follicle or concentrations of progesterone in plasma. Emergence of preovulatory follicles closer to the time of removal of inserts reduced the diameter of the ovulatory follicle when oestrus was induced with ODB. Ovulation of smaller follicles reduced concentrations of progesterone in plasma following ovulation but did not affect oestrous cycle duration.     

Ovarian follicle development in wapiti (Cervus elaphus) during the anovulatory season

The ovaries of 12 mature wapiti hinds were studied by transrectal ultrasonography during the anovulatory season to characterize follicular dynamics and to test the hypothesis that follicle development occurs in a wave-like fashion. The hinds were examined daily, standing without sedation. Follicle size and numbers were recorded, and individual follicles were identified serially. Follicle development was considered wave-like if periodic changes in follicle numbers could be associated temporally with the development of a dominant follicle. There were non-random changes (P<0.01) in the number of follicles > or =4 mm in diameter detected per day. Each peak in follicle numbers was associated with the development of a single dominant follicle. The dominant follicle of the cohort was larger (P<0.05) than the other follicles 1 day after its emergence. Intervals between successive peaks (6.8 +/- 0.4 day) and troughs (6.8 +/- 0.4 day) in follicle numbers, and emergence of sequential dominant follicles (7.1 +/- 0.5 day) were not different (P=0.86). Results confirmed the hypothesis that ovarian follicles develop in a wave-like fashion in wapiti during the anovulatory season.     

Role of the double luteinizing hormone peak, luteinizing follicles, and the secretion of inhibin for dominant follicle selection in Asian elephants (Elephas maximus)

Elephants express two luteinizing hormone (LH) peaks timed 3 wk apart during the follicular phase. This is in marked contrast with the classic mammalian estrous cycle model with its single, ovulation-inducing LH peak. It is not clear why ovulation and a rise in progesterone only occur after the second LH peak in elephants. However, by combining ovarian ultrasound and hormone measurements in five Asian elephants (Elephas maximus), we have found a novel strategy for dominant follicle selection and luteal tissue accumulation. Two distinct waves of follicles develop during the follicular phase, each of which is terminated by an LH peak. At the first (anovulatory) LH surge, the largest follicles measure between 10 and 19.0 mm. At 7 ± 2.4 days before the second (ovulatory) LH surge, luteinization of these large follicles occurs. Simultaneously with luteinized follicle (LUF) formation, immunoreactive (ir) inhibin concentrations rise and stay elevated for 41.8 ± 5.8 days after ovulation and the subsequent rise in progesterone. We have found a significant relationship between LUF diameter and serum ir-inhibin level (r(2) = 0.82, P < 0.001). The results indicate that circulating ir-inhibin concentrations are derived from the luteinized granulosa cells of LUFs. Therefore, it appears that the development of LUFs is a precondition for inhibin secretion, which in turn impacts the selection of the ovulatory follicle. Only now, a single dominant follicle may deviate from the second follicular wave and ovulate after the second LH peak. Thus, elephants have evolved a different strategy for corpus luteum formation and selection of the ovulatory follicle as compared with other mammals.     

Follicle and systemic hormone interrelationships during spontaneous and ablation-induced ovulatory waves in mares

The characteristics of ovulatory follicular waves were studied for spontaneous waves and waves induced during the next estrous cycle by ovarian follicle ablations and administration of PGF2alpha 10 days after ovulation in 21 mares. In the induced group, both the days of the FSH surge and day of deviation were more synchronized, LH concentrations were greater before and after deviation, estradiol concentrations were greater after deviation, and the ovulatory follicle grew at a faster rate (3.4+/-0.2 compared with 2.7+/-0.1 mm/day). The frequency of two dominant follicles/wave was not different between induced waves (7 of 21) and spontaneous waves (9 of 21), but both dominant follicles ovulated more frequently in induced waves (6 of 7 waves compared with 0 of 9).     

Origin of the preovulatory follicle in Mouflon sheep (Ovis gmelini musimon) and effect on growth of remaining follicles during the follicular phase of oestrous cycle

Daily transrectal ultrasonographies were conducted to study development of all follicles with antral diameters > or = 2mm during the follicular phase of oestrous cycle in Mouflon, a strictly monovular wild-sheep. A total of 14 follicular phases was studied after oestrus synchronization with two cloprostenol doses, 9 days apart, in five cyclic Mouflon ewes. In 13 cycles (92.8%), the ovulatory follicle arose from those antral follicles present in both ovaries when luteolysis was induced, being the largest one with a mean size of 4.4+/- 0.3mm at that moment in 10 cycles (76.9%). The remaining cycles had a larger follicle, but it was decreasing in size. Appearance of new follicles > or =2mm in size remained unaffected during the follicular phase (3.7+/- 0.2), but there was found a linear decrease in the number of those growing to > or =3mm (2.5+/- 0.4 to 1.1+/- 0.2, P < 0.05) and > or = 4mm (0.6+/- 0.2 to 0.1+/- 0.1, P < 0.005), detection of new follicles growing to > or = 5mm was negligible. Then, number of medium (4-5mm) growing follicles present in both ovaries decreased from 1.5+/- 0.3 at 0 h to 0.3+/- 0.1 at 72 h (P<0.005). In conclusion, the single ovulatory follicle is the largest growing follicle present in both ovaries at the moment of luteolysis. This follicle is selected to grow and ovulate while development of other follicles is inhibited.     

Ovarian follicular dynamics in heifers during early pregnancy

Daily ultrasonic monitoring of individual follicles was used to compare follicular wave characteristics of nonbred (n = 6) and pregnant heifers (n = 6). The dominant follicle of the first wave (Wave 1) did not differ significantly between reproductive statuses for any endpoint. The dominant follicle of Wave 2 was the ovulatory follicle in all nonbred heifers. The maximum diameter of the dominant follicle of Wave 2 was greater (p less than 0.05) for the nonbred heifers (14.8 mm) than for the pregnant heifers (13.0 mm). The dominant follicle of Wave 3 was detected later (p less than 0.003; Day 19.7 vs. Day 17.3) and reached a greater diameter (p less than 0.05; 16.6 mm vs. 12.0 mm) in the nonbred than in the pregnant heifers. On the mean day of onset of luteolysis (Day 15.2) in the nonbred heifers, the dominant follicle was similar in diameter for the two groups. Within a few days, the follicle began to regress in the pregnant heifers but maintained or increased in diameter in the nonbred heifers so that a greater maximum diameter was attained. During Days 0 70 of pregnancy, the interval from emergence of a wave to the emergence of the next wave was constant (not significantly different; mean intervals, 8.5 9.8 days). The mean maximum diameter attained by the dominant follicles differed significantly among the first 6 follicular waves; diameter was greatest for Wave 1 (15.7 mm), smallest for Waves 2 (13.1 mm) and 3 (12.6 mm), and intermediate for Waves 4 (14.0 mm), 5 (13.7 mm), and 6 (14.5 mm).(ABSTRACT TRUNCATED AT 250 WORDS)     

Progestagen synchronisation in the absence of a corpus luteum results in the ovulation of a persistent follicle in cyclic ewe lambs

Progestagens are widely used to synchronise oestrous in sheep but the effects on follicular dynamics are not clear. We tested the hypothesis that when luteolysis occurs early during progestagen synchronisation prolonged growth of the ovulatory follicle will occur. Cyclic ewe lambs (40.0+/-0.3 kg) were divided into three groups: eight ewes (Long group) received a progestagen sponge (60 mg medroxyprogesterone acetate) from Days 5 to 19 after oestrous and eight ewes (Short group) received a progestagen sponge on Day 5 which was replaced on Day 10 and again on Day 15, and removed on Day 19 after oestrous. On Days 6 and 7, ewes in both groups received prostaglandin. A third group (n=5, Control) did not receive any treatment. The growth and development of follicles > or =2 mm in diameter were characterised using daily transrectal ultrasonography. On Day 18, blood samples were collected every 12 min for 8 h from five ewes in the Long and Short groups. Data were analysed by ANOVA. The maximum diameter and age (emergence to ovulation) of the ovulatory follicle was greater (P<0.01) in ewes in the Long group (7. 4+/-0.2 mm and 12.1+/-0.6 days) than in ewes in the Short group (6. 3+/-0.2 mm and 5.1+/-0.5 days) and Control group (6.3+/-0.4 mm and 6. 8+/-0.6 days). On Day 18 of the cycle, LH pulse frequency and oestradiol concentrations were greater (P<0.05) in ewes in the Long group (3.2+/-1.1 pulse per 8 h and 1.15+/-0.09 pg ml(-1)) than the Short group (0.8+/-0.4 pulses per 8 h and 0.54+/-0.08 pg ml(-1)).We suggest that the negative feedback efficacy of a long-term progestagen sponge decreased with time and led to an increase in LH pulse frequency and prolonged growth of the ovulatory follicle. We conclude that, in the absence of luteal progesterone, synchronisation with a single progestagen sponge for 14 days resulted in higher LH pulse frequency and ovulation of a persistent follicle with a larger maximum diameter, compared with controls.     

Superovulatory response in anestrous ewes is affected by the presence of a large follicle

Superovulatory response to conventional treatment with eCG (1200 IU) and progestagen sponges (MAP, n = 9; FGA, n = 9; or controls without sponge, n = 6) was studied in Corriedale anestrous ewes. The follicular population just before the administration of eCG and the total ovarian response (large anovulatory follicles plus normal CL and prematurely regressing CL) to treatment were determined after laparotomy. Pretreatment with progestagen did not modify the number or class of follicles greater than 1 mm observed on the ovarian surface at the time of eCG administration (19 +/- 2.2 follicles vs 19 +/- 2.9 follicles, for pooled progestagen-treated groups and control groups, respectively; mean +/- SEM) but significantly decreased the number of large anovulatory follicles (4.7 +/- 1.0 vs 10.2 +/- 2.6; P < or = 0.01) observed following treatment. Progestagen-treated animals were classified according to the presence (n = 13) or absence (n = 5) of a large follicle (LF: > or = 4 mm diameter) on the ovarian surface at the time of eCG treatment; a qualitatively better superovulatory response was observed in ewes without large follicle (large anovulatory follicles: 1.6 +/- 0.7 vs 5.8 +/- 1.3, P < or = 0.05; normal CL: 7.0 +/- 1.4 vs 3.8 +/- 1.0, P < or = 0.1; normal CL/total ovarian response: 78.7 +/- 10.1 % vs 34.9 +/- 8.2 %, P < or = 0.01; for ewes without LF and ewes with 1 to 2 LF respectively). No differences were observed in the individual ovulatory response when comparing ovaries ipsilateral or contralateral to LF in a same animal, indicating that the effect of LF on the superovulatory response would be fundamentally systemic. This work shows that, similar to what occurs in cows, the presence of a large follicle at the time of gonadotropin administration decreases the superovulatory response in anestrous ewes.     

Is slow follicular growth the cause of silent estrus in water buffaloes?

The present experiment was conducted to study the growth profile of the ovulatory follicle in relation to the expression of estrus following administration of PGF(2alpha) to subestrus buffaloes. After detection of a mature corpus luteum by examination per rectum, confirmed by ultrasound scanning, subestrus buffaloes (n=20) were treated (Day 0) with single dose of Dinoprost tromethamin (25 mg, i.m.). Blood samples were collected at 0, 24 and 48 h after treatment for estimation of plasma progesterone concentration. Growth profile of the ovulatory follicle was monitored daily through ultrasound scanning starting from Day 0 until ovulation and the regression profile of CL was monitored at 0, 24 and 48 h of treatment. Estrus was detected by exposure to a fertile buffalo bull three times a day until expression of overt estrus or ovulation. Behavioral estrus was recorded in 14 animals and 6 animals ovulated silently. Sixteen animals including six animals with silent estrus ovulated from the dominant follicle present at treatment (Group A) and remaining four animals ovulated from the dominant follicle of succeeding follicular wave (Group B). The intervals from treatment to estrus (6.5+/-0.25 versus 3.2+/-0.27 days, P<0.001) and treatment to ovulation (7.5+/-0.25 versus 5.4+/-0.46 days, P<0.005) were significantly longer in animals of Group B compared with animals of Group A. Significant differences were observed in growth profile of the ovulatory follicle between animals of Groups A and B with respect to size of the follicle on Day 0 (9.8+/-0.7 versus 5.3+/-0.45 mm, P<0.001), daily growth rate (0.97+/-0.07 versus 1.6+/-0.2 mm/day, P<0.01) and increase in diameter (4.1+/-0.6 versus 7.8+/-0.7 mm, P<0.01). The animals with silent estrus (subgroup A-2) had significantly smaller diameter of the ovulatory follicle on Day 0 (7.7+/-0.4 versus 11.0+/-0.7 mm, P<0.005), its daily growth rate was significantly slower (0.7+/-0.02 versus 1.1+/-0.1 mm/day, P<0.01) and they recorded significantly longer interval from treatment to ovulation (7.3+/-0.56 versus 4.2+/-0.27 days, P<0.001) compared with the animals that showed overt estrus (subgroup A-1). The corpus luteum area (CL area) and plasma progesterone (P(4)) concentration declined continuously from 0 to 48 h after PGF(2alpha) treatment in the animals of both the Groups A and B. Non-significant differences were observed in mean CL area and plasma P(4) concentration at 0, 24 and 48 h post-treatment between animals of Groups A and B and also between animals of subgroups A-1 and A-2. The small size and the slow growth rate of the ovulatory follicle were identified as the possible cause of silent estrus in subestrus buffaloes after PGF(2alpha) treatment.     

Follicular growth monitoring in the female cat during estrus

Follicular growth in the feline ovary is usually detected indirectly, through behavior observation, vaginal smears, or more invasively, by estradiol assay in blood. This study was designed to describe follicular dynamics by transabdominal ultrasonography. Secondly, the stage of follicular growth was associated to behavioral and vaginal changes. Ovarian ultrasonography was performed during nine anovulatory and 12 ovulatory cycles. Forty-eight follicles were followed during anovulatory cycles: on the first day of estrus behavior, 4.8 ± 0.2 follicles (2 to 7 per female) of 2.3 ± 0.01 mm mean diameter were present. Follicular growth continued at a rate of 0.2 ± 0.04 mm per day. At least one follicle in the cohort reached a diameter greater than 3.0 mm. Maximal follicular growth (when one follicle of the cohort reached the maximal diameter observed for the whole estrus) was reached 3.8 ± 0.3 days after the onset of estrus with the largest follicle reaching a diameter of 3.5 ± 0.04 mm. Growth of the various follicles within a cohort was not exactly synchronous. When no ovulation took place, the follicular diameter decreased by 0.1 ± 0.01 mm per day until the end of estrus. The first day after the end of behavioral estrus, the diameter of the largest follicle in each cohort was 2.7 ± 0.05 mm. No correlation was found between follicular development and either vaginal smear characteristics, or time elapsed since the onset of estrus. When ovulations were mechanically induced after one follicle had reached 3.0 mm in diameter, artificial insemination produced normal pregnancy rate and litter size: four pregnant females out of nine, and 2 to 4 kittens per litter. Ultrasonography proved thus to allow the monitoring of follicular growth in the female cat, with low correlation with behavior and vaginal smear modifications. Further studies are needed to evaluate the interest of an ultrasonographic ovarian follow-up to determine the optimal moment for ovulation induction prior to artificial insemination.     

Supplementation of equine early spring transitional follicles with luteinizing hormone stimulates follicle growth but does not restore steroidogenic activity

This study was conducted to test the hypothesis that supplementation of growing follicles with LH during the early spring transitional period would promote the development of steroidogenically active, dominant follicles with the ability to respond to an ovulatory dose of hCG. Mares during early transition were randomly assigned to receive a subovulatory dose of equine LH (in the form of a purified equine pituitary fraction) or saline (transitional control; n = 7 mares per group) following ablation of all follicles >15 mm. Treatments were administered intravenously every 12 h from the day the largest follicle of the post-ablation wave reached 20 mm until a follicle reached >32 mm, when an ovulatory dose of hCG (3000 IU) was given. Saline-treated mares during June and July were used as ovulatory controls. In a preliminary study, injection of this pituitary fraction (eLH) to anestrus mares was followed by an increase in circulating levels of LH (P < 0.01) but not FSH (P > 0.6). Administration of eLH during early transition stimulated the growth of the dominant follicle (Group x Day, P < 0.00001), which attained diameters similar to the dominant follicle in ovulatory controls (P > 0.1). In contrast, eLH had no effect on the diameter of the largest subordinate follicle or the number of follicles >10 mm during treatment (P > 0.3). The numbers of mares that ovulated in response to hCG in transitional control, transitional eLH and ovulatory control groups (2 of 2, 3 of 5 and 7 of 7, respectively) were not significantly different (P > 0.1). However, after hCG-induced ovulation, all transitional mares returned to an anovulatory state. Circulating estradiol levels increased during the experimental period in ovulatory controls but not in transitional eLH or transitional control groups (Group x Day, P = 0.013). In addition, although progesterone levels increased after ovulation in transitional control and transitional eLH groups, levels in these two groups were lower than in the ovulatory control group after ovulation (Group, P = 0.045). In conclusion, although LH supplementation of early transitional waves beginning after the largest follicle reached 20 mm promoted growth of ovulatory-size follicles, these follicles were developmentally deficient as indicated by their reduced steroidogenic activity.