Impact of exogenous progesterone on ovarian follicular dynamics and function in mice.

Raising progesterone concentrations in young adult mice by subcutaneous implants resulted in ovulation being blocked and the cessation of oestrous cycles. The effect of this treatment on the numbers and dynamics of preantral follicles during 36 days of treatment was studied using a compartmental model to analyse differential follicle counts. Changes in growth and/or death rates were detected at all stages of follicular development. An increased rate of growth through preantral stages was predicted in the treatment group when compared with the controls, but most of these follicles did not reach the antral stage of development as an increased death rate was observed at large preantral stages (stage IV). Antral follicles were formed in the treatment group, but all succumbed to atresia. Increased atresia in the antral population of follicles in the treatment group was observed directly.     

Follicular activity and hormonal secretory profile in vicuna (Vicugna vicugna)

The objective of the present study was to characterize ovarian activity in non-mated vicunas, relating ovarian structures (evaluated by transrectal ultrasonography, daily for 30 days) to changes in plasma concentrations of estradiol-17beta and progesterone. Ovarian follicular activity occurred in waves, characterized by the follicle emergence, growth and regression. The mean duration of follicular waves was 7.2+/-0.5 days (mean+/-S.E.M.), with a range of 4-11 days. The follicular growth phase averaged 3.0+/-0.2 days, the static phase 1.4+/-0.1, the regression phase 2.9+/-0.3 days, and the inter-wave interval was 4.2+/-0.3 days. The mean growth rate during the growing phase was 1.8+/-0.1mm/day, while the duration of the interval from 6mm to maximum diameter was 1.4+/-0.1 days. The mean maximum diameter of the dominant follicle was 8.4+/-0.3mm (range: 6.2-11.2) and mean diameter of the largest subordinate follicle was 5.4+/-0.1mm. There was an inverse relationship between the size of the largest follicle and the total number of follicles (r=-0.21, P=0.002). Follicle activity alternated between ovaries in 77% of the waves, with 40% of dominant follicles present in the left ovary and 60% in the right ovary. Plasma estradiol-17beta concentrations also had a wave-like pattern, varying between 12.0 and 62.8 pmol/l. Plasma progesterone concentrations remained below 5.0 nmol/l and there was no ultrasonographic evidence of ovulation during the study.     

Effects of exogenous progesterone and cloprostenol on ovarian follicular development and first ovulation in prepubertal heifers

The objective of this study was to determine the effects of progesterone and cloprostenol (a PGF_2α analogue) on ovarian follicular development and ovulation in prepubertal heifers. In Experiment 1, crossbred Hereford heifers (Bos taurus; 10 to 12 mo old, 255 to 320 kg) were assigned randomly to three groups and given (1) an intravaginal progesterone-releasing insert (CIDR; P group, n = 13); (2) a CIDR plus 500 μg cloprostenol im (PGF_2α analogue) at CIDR removal (PPG group, n = 11); or (3) no treatment (control group, n = 14). The CIDR inserts were removed 5 d after follicular wave emergence. Progesterone-treated heifers (P and PPG groups) had a larger dominant follicle than that of the control group (P = 0.01). The percentage ovulating was highest in the PPG group (8 of 11, 73%), intermediate in the P group (4 of 13, 31%), and lowest in the control group (1 of 14, 7%; P < 0.02). In Experiment 2, 16 heifers (14 to 16 mo old, 300 to 330 kg) were designated to have follicular wave emergence synchronized with either a CIDR and 1 mg estradiol benzoate im (EP group, n = 8) on Day 0 (beginning of experiment) or by transvaginal ultrasound-guided ablation of all follicles ≥5 mm on Day 3 (FA group, n = 8). On Day 7, CIDRs were removed in the EP group, and all heifers received 500 μg cloprostenol im. Ovulation was detected in 6 of 8 heifers (75%) in both groups. In summary, the use of PGF_2α with or without exogenous progesterone treatment increased the percentage ovulating in heifers close to spontaneous puberty.     

Relationship between endogenous progesterone and follicular dynamics in lactating dairy cows with ovarian follicular cysts

Two experiments were conducted to examine circulating concentrations of progesterone (P4) in cows with ovarian follicular cysts (OFCs) and to relate differing levels of P4 to subsequent follicular events. In experiment 1, peripheral concentrations of P4 were determined in cows diagnosed with OFCs. Nonpregnant, lactating Holstein and Jersey cows (n = 32) were diagnosed as having OFCs by rectal palpation. Ovarian follicular cysts were then examined by transrectal ultrasonography to confirm the presence of OFCs (follicle diameter, >/=17 mm; absence of luteal tissue). At confirmation, a blood sample was collected for quantification of P4. The concentration of P4 at confirmation was classified as low (<0.1 ng/ml), intermediate (0.1-1.0 ng/ml), or high (1.0-2.0 ng/ml). More OFCs were associated with intermediate (66%) than with either low (28%) or high (6%) concentrations of P4. In experiment 2, the fate of follicles (diameter, >/=10 mm) that formed in the presence of an OFC was determined and related to circulating concentrations of P4 during follicular development. Follicles (n = 59) that formed in the presence of an OFC ovulated (n = 19), formed a cyst (n = 30), or underwent normal growth and regression (NGR; n = 10). Endogenous P4 in the 7-day period during follicular development was classified as low (if P4 dropped to <0.1 ng/ml for 1 day or longer), intermediate (if P4 averaged between 0.1 and 1.0 ng/ml and never dropped to <0.1 ng/ml), or high (if P4 averaged >1.0 ng/ml and never dropped to <0.1 ng/ml). In the presence of intermediate P4, 75% of observed follicles formed cysts, compared with 10% that ovulated and 15% that experienced NGR. In the presence of low P4, 53%, 41%, and 6% of follicles ovulated, formed a follicular cyst, or experienced NGR, respectively. Thus, an association between intermediate P4 and the formation of OFCs was established.     

Recovery of Trichuris tenuis Chandler, 1930, from camelids (Lama glama and Vicugna vicugna) in Argentina

A survey of whipworms was conducted in llamas and vicu?as in northwestern Argentina. Fecal examinations of a group of 14 llamas (April 1995-March 1996) and 69 vicu?as (November 1996) indicated a high prevalence (usually >50%) of Trichuris sp. in these hosts. Prevalence was highest during July-November 1995 that also coincided with the highest mean fecal egg count. During postmortem examinations of 1 llama and 1 vicu?a, specimens of Trichuris tenuis were recovered from the cecum/large intestine of each camelid. This is the first report of T. tenuis in South America, and the first report in the vicu?a. It is suggested that T. tenuis is the typical whipworm of aboriginal camelids.     

Characterization of ovarian follicular dynamics in dromedary camels (Camelus dromedarius)

Ovarian follicular dynamics was monitored by transrectal ultrasonography, for a period of 60 to 90 days, and its correlation with plasma estradiol-17β (E2) and progesterone (P4) were studied in seventeen, multiparous, non-lactating, 12 to 20-year-old dromedary camels. The average number of follicles recruited (12.77 ± 0.93) in each wave between animals varied (P < 0.001). The number of follicles recruited during different follicular waves was highly repeatable (0.95) within individual animals. The growth and mature phase periods of the dominant follicle (DF) were 6.10 ± 0.15 and 10.20 ± 0.47 days, respectively with a linear growth rate of 1.17 ± 0.02 mm/day between Day 0 and 10 of the follicular wave. There was an inverse relationship between the diameter of the largest DF and number of follicles (r = −0.95, P < 0.001). The DF development did not regularly alternate between the ovaries and the incidence of codominance was 45%. The mean maximum diameter of DF during its mature phase was 27.30 ± 0.78 mm and oversized follicle was 38.43 ± 1.41 mm. In 73.3% waves, the DF continued its growth for a period of 10.64 ± 1.53 days even after losing its dominance and developed into oversized follicle. The duration of the regression phase of DF and oversized follicle were 24.71 ± 3.79 and 18.50 ± 2.23 days. The mean duration of a complete follicular wave was 47.11 ± 2.94 days with an interwave interval (IWI) of 16.36 ± 0.37 days. The IWI within an individual was repeatable (0.88) and between the animals was variable (P < 0.001). Plasma E2 concentration profiles showed a wave like pattern. The peak plasma E2 concentrations were attained approximately 12 days after beginning of the growth phase, when the largest DF grew to a diameter of 18.7 mm. Plasma concentration of P4 was below 1.0 ng/mL in 85% of waves and above 1.0 ng/mL in 15% of the waves for a period of 3 to 6 days in the absence of spontaneous ovulation. It is concluded that ovarian follicular development and plasma E2 concentrations occurs in a wave like pattern in dromedary camels and the IWI and follicle numbers recruited per wave are variable between the animals and repeatable within an individual animal.     

Effect of treatment with progesterone and oestradiol when starting treatment with an intravaginal progesterone releasing insert on ovarian follicular development and hormonal concentrations in Holstein cows

Ovarian follicular development and concentrations of gonadotrophin and steroid hormones were studied in non-lactating Holstein cows following administration of progesterone (P(4)) or oestradiol benzoate (ODB) at the start of treatment with an intravaginal progesterone releasing insert (IVP(4)) in a 2 by 2 factorial experiment. Cows were treated at random stages of the oestrous cycle with an IVP(4) device (Day 0) and either no other treatment (n=8), 200 mg of P(4) IM (n=9), 2.0 mg of ODB IM (n=8) or both P(4) and ODB (n=9). Seven days later devices were removed and PGF(2alpha) was administered. Twenty-four hours later 1.0mg of ODB was administered IM. Oestrus was detected in 97.1% and ovulation in 64.7% (effect of treatment, P=0.41) of cows within 96 h of removing inserts. In the cows that ovulated, day of emergence of the ovulatory follicle was delayed (P<0.01) and more precise (P<0.05) in cows treated with ODB compared to the cows treated with P(4). Interval from wave emergence to ovulation and the diameter of the ovulatory follicle was less (P<0.05) in cows treated with ODB compared to cows treated with P(4). Combined treatment with P(4) and ODB at the time of starting treatment with an IVP(4) device did not significantly change the pattern of ovarian follicular development compared to treatment with ODB alone. Concentrations of LH and FSH in plasma were less in cows treated with ODB between Days 0 and 4 (P<0.05) while treatment with P(4) increased concentrations of FSH in plasma between Days 0 and 4 (P<0.05). When anovulatory cows were compared to ovulatory cows, diameters of follicles (P<0.001) and growth rate of follicles (P<0.01) were less in anovulatory cows between Days 7 and 9, while concentrations of FSH in plasma were greater (P<0.01), concentrations of LH similar (P>0.90) and concentrations of oestradiol were less (P=0.01) in the anovulatory cows between Days 4 and 10. Our findings support a hypothesis that ovarian follicular development following administration of P(4) or ODB at the start of treatment with an IVP(4) device differs. Anovulatory oestrus may have been associated with reduced maturity and/or later emergence of ovarian follicles.     

Changes in follicular populations following treatment of buffaloes with PMSG (eCG) and Neutra-PMSG for superovulation.

Some 19 buffaloes were synchronized by administration of a prostaglandin (PG) salt Lutalyse, with a single intramuscular (i.m.) injection of 25 mg at day -13. Luteolysis was induced by administration of 50 mg PG, in divided doses of 30 and 20 mg i.m. 12 h apart on day 0 of experiment. The 30 mg PG injection was designated as 0 h of experiment. Group I animals (n = 6) received saline and served as controls while animals in Groups II (n = 7) and III (n = 6) received 2500 I.U. PMSG (eCG) i.m. at day -2. Group III animals were administered 5 ml Neutra-eCG intravenously at 60 h. The number of follicles, classified on the basis of diameter as small (2-5 mm), medium (6-9 mm) and large (> or = 10 mm) was assessed by ultrasonography on days -2, -1, 0, 1, 2, 5 and 7 of experiment. The number of corpora lutea (CL) was recorded by palpation per rectum on day 8. The number of small follicles which did not differ among the three groups on days 0, 1 and 2 was significantly lower (P < 0.05) in Group II animals compared to those in Groups I and III on days 5 and 7. The number of medium follicles increased after eCG treatment and was significantly higher (P < 0.05) in animals of Groups II and III on days 0 and 1, compared to control animals of Group I. It was, however, not different among the three groups on subsequent days of experiment. The number of large follicles which did not differ among the three groups on days -2, 0, 1 and 2 was significantly higher in Groups II (P < 0.01) and III (P < 0.05) animals compared to those of Group I on day 5. On day 7, the number of large follicles was in the order (P < 0.05) Group II > Group III > Group I. The number of CL in Group II animals was significantly higher (P < 0.05) than that in Group I animals but was not different from that of Group III animals. These results suggest that treatment of buffaloes with eCG for superovulation reduces the number of small follicles and increases the number of large follicles 5-7 days after PG treatment. Administration of Neutra-eCG 60 h after PG treatment can partly reverse this trend but has no effect on ovulation rate. The possibility that part of the variability in ovulation rates in this study may have resulted from Neutra-eCG been given prior to or at the LH surge, or from the absence or presence of a dominant follicle at the time of eCG treatment cannot be ruled out.     

Effect of exogenous progesterone and oestradiol on plasma progesterone concentrations and follicle wave dynamics in anovulatory anoestrous post-partum dairy cattle

The effect of exogenous progesterone (P4) and of oestradiol benzoate (ODB) on plasma progesterone concentration and follicle dynamics was studied in anovulatory anoestrus (AA) post-partum pasture-fed dairy cattle. Cows (n=32) were defined AA based on not detecting a corpus luteum upon transrectal ultrasonography of the ovaries. Cows were randomly assigned to treatment with an intravaginal P4-releasing device containing 1.56 g of P4 (1Q; Cuemate, Pfizer Animal Health, Auckland, NZ; n=11) or with modified devices with double (2Q; n=11) or triple (3Q; n=10) the normal P4 dose for 8 days. Half of each group received 2 mg ODB at device insertion (Day 0) while the other half did not receive ODB at this time. All cows were treated with 1 mg ODB 1 day after intravaginal device removal (Day 9). Ultrasonography occurred daily until either ovulation or Day 15 whichever occurred sooner. Blood samples were drawn on Days 0, 1, 3, 5, 7, 8, 9, 15 and 22 for plasma P4 determination. Increasing P4 dose was associated with an increase in plasma P4 concentration during the time of device insertion (P <0.05). The highest P4 dose was associated with a delay in emergence of, but a shorter interval from emergence to maximum diameter and ovulation of, the subsequent dominant follicle (DF2) compared to the lowest P4 dose. Treatment with ODB resulted in a delay in emergence of DF2 (4.2 (0.4) versus 2.0 (0.4) days (S.E.M.) to emergence for ODB versus no-ODB; P=0.01), a smaller maximum diameter of DF2 (15.2 (0.5) versus 17.9 (0.6)mm (S.E.M.) for ODB versus no-ODB; P <0.01), a shorter interval to maximum DF2 diameter (5.0 (0.3) versus 6.8 (0.3) days (S.E.M.) for ODB versus no-ODB; P=0.03), a shorter interval from DF2 emergence to ovulation (6.3 (0.4) versus 8.5 (0.4) days (S.E.M.) for ODB versus no-ODB; P=0.02) and a tendency for a lower average plasma P4 concentration post-ovulation (i.e. average of Days 15 and 22; 2.5 (0.4) versus 3.4 (0.4) ng/ml plasma P4 for ODB versus no-ODB, respectively; P=0.08). The DF present at device insertion, was still present at device removal in three (9%) cows of which two were treated with 1Q + no-ODB and one with 3Q + ODB. It is concluded that increasing P4 dose and ODB treatment are associated with a delay in subsequent follicle wave emergence and more rapid follicle growth. Oestradiol benzoate treatment also tends to reduce the plasma P4 concentration in the subsequent luteal phase in post-partum, anoestrous dairy cattle.     

Local versus systemic effects of exogenous estradiol-17 beta on ovarian follicular dynamics in heifers with progestogen implants

Two experiments were designed to determine if the suppressive effect of estradiol treatment on ovarian follicles in progestogen-implanted heifers is mediated directly at the ovary or systemically, at a higher level. The purpose of Experiment 1 was to determine a minimal effective dose of estradiol-17beta (E-17beta) that would induce follicle regression in progestogen-implanted heifers. Beef heifers were implanted with progestogen on Day 2 (Day 0=ovulation) and were assigned randomly to five groups: control (sesame seed oil, n=9); 0. 1 mg of E-17beta (n=8); 0.5 mg of E-17beta (n=8); 1 mg of E-17beta (n=8); or 5 mg of E-17beta (n=8) by intramuscular (im) injection on Day 3. Treatment with 5 and 1 mg of E-17beta resulted in smaller (P<0.05) day-to-day diameter profiles of the dominant follicle compared with controls, whereas 0.1 mg of E-17beta did not have an apparent effect on follicle growth. The effect of a dose of 0.5 mg was intermediate and tended (P<0.06) to result in a smaller diameter profile of the dominant follicle compared with control heifers. Experiment 2 was designed to utilize a subminimal dose of E-17beta (0.1 mg), locally, to determine whether estradiol treatment induces follicle regression through a direct action on the ovary. Beef heifers received a progestogen ear implant on Day 2 and were assigned randomly to five groups on Day 3: control (sesame seed oil, n=8); 5 mg of E-17beta im (n=8); 0.1 mg of E-17beta im (n=8); 0.1 mg of E-17beta given into the wall of the uterus, near the tip of the horn ipsilateral to the dominant follicle (intrauterine (iu), n=8); or 0.1 mg of E-17beta given into the stroma of the ovary, immediately adjacent to the dominant follicle (intraovarian (io), n=6). Local (iu and io) treatments were given via a transvaginal ultrasound-guided needle injection. Treatment with 5 mg of E-17beta im resulted in suppression of the dominant follicle of the first follicular wave and early emergence of the second follicular wave (P<0.05). Diameter profiles of the dominant follicle in heifers treated with 0.1 mg im or 0.1 mg iu differed from those of control heifers on Day 5, whereas diameter profiles of the dominant follicle in heifers treated with 0.1 mg io did not differ from the controls. Daily changes in diameter of the dominant follicle did not differ among the three groups treated with 0.1 mg of E-17beta (im, iu and io). Hourly changes in circulating concentrations of FSH and LH were not detected following estradiol treatment either before or after the results were combined for all estradiol-treated groups. Results are supportive of the hypothesis that the suppressive effect of estradiol in cattle is exerted indirectly through a systemic route rather than directly at the ovary. Although low plasma concentrations of FSH and LH were not detected, systemic treatments with high E-17beta dosages resulted in follicular suppression whereas local treatments with subminimal dosages, within the ovary bearing the dominant follicle, were without effect.     

Postpartum ovarian follicular dynamics in primiparous and pluriparous Mediterranean Italian buffaloes (Bubalus bubalis)

The objective of this study was to monitor ovarian function in postpartum primiparous and pluriparous Mediterranean Italian buffaloes (Bubalus bubalis) during months of increasing daylength. Ovarian ultrasound monitoring was carried out for a total of 60 days from calving in 10 primiparous and 10 pluriparous buffaloes. Progesterone was determined from calving until a week after first postpartum ovulation. The study was undertaken during months of increasing day length. Time required for complete postpartum uterine involution was 31 +/- 1.0 and 33 +/- 1.3 days in primiparous and pluriparous buffaloes respectively (P = 0.1). The first postpartum ovulation was recorded on 4 primiparous and 8 pluriparous buffaloes (P = 0.16). Time for first postpartum ovulation to occur was 25.5 +/- 6.9 and 15.5 +/- 1.3 days in primiparous and pluriparous buffaloes, respectively (P = 0.07). Overall, 8 of the 12 first postpartum ovulations (66.6%) occurred in the ovary contra-lateral to the one bearing the gravidic CL, one out of 4 in primiparous and 3 out of 8 in pluriparous buffaloes (P = 1.0). Following a first postpartum ovulation, 3 primiparous and 4 pluriparous buffaloes displayed a complete wave of follicular development leading to a new ovulation. Ovulation following parturition was not recorded in 6 primiparous and two pluriparous buffaloes for the 60 days of ultrasound monitoring. Growth rate (mm/d) and largest size (mm) of first postpartum ovulating follicle was 0.95 +/- 0.18 and 1.07 +/- 0.07 (P = 0.4), and 13.5 +/- 0.8 and 14.1 +/- 0.4 (P = 0.4) in primiparous and pluriparous buffaloes, respectively. Following calving, the total number of available antral follicles (> or =2 mm) declined gradually towards the end of the study period. Follicles greater or equal to 3 mm in diameter on the contrary showed a prominent increase in the first 2 weeks from calving. The number of follicles greater or equal to 3 mm in diameter was significantly higher in the ovary contra-lateral to the one bearing the gravidic CL. A balance in the number of such follicles was reached toward the end of the first month. In conclusion, although some follicular activity was recorded in the ovaries of all buffaloes, true postpartum resumption of cyclicity in the months of increasing daylight hours was delayed in the majority of animals.     

The effect of subluteal levels of exogenous progesterone on follicular dynamics and endocrine patterns during early luteal phase of the ewe

Nineteen Corriedale ewes were treated with an im dose of a PGF2alpha during the luteal phase to synchronize estrus. After ovulation had been detected by using ultrasonography (Day 0); the ewes were randomly assigned to 2 different groups. In 11 ewes a CIDR, which had previously been used for 10 d, was inserted on the fourth day after ovulation. The ewes then received a dose of PGF2alpha on Day 5 to induce luteolysis. The CIDR remained in place until the end of the experiment (Day 9). Control ewes (n = 8) received no treatment. Blood samples were taken daily for estradiol, progesterone and FSH determinations. In the untreated ewes, 2 follicular waves were detected in all of the animals throughout the monitoring period, with a mean wave interval of 4.5 d. The total number of follicles which were > or =2 mm decreased from Day 0 to Day 4 (8.8+/-1.0 to 5.3+/-0.6; P< or =0.05) and then increased at Day 7 (7.5+/-0.9; P< or =0.05). The growth profiles of both the largest and the second largest follicles of Wave 1 showed significant divergence, while no divergence was observed in Wave 2. Serum estradiol concentrations decreased significantly from the day before to the day of ovulation and then increased again during the growing phase of the largest follicle of Wave 1. Concentrations of FSH were high on the day of emergence of both waves, but while a significant decline was observed after emergence in Wave 1, the levels remained high in Wave 2. In 8 of the 11 treated ewes, the largest follicle of Wave 1 was still present on the ninth day after ovulation (persistent follicle). In the other 3 ewes, the largest follicle of Wave 1 was already regressing on the day that the treatment was administered, and the largest follicle that was present on Day 9 originated from Wave 2 (nonpersistent follicle). In persistent follicle ewes, the largest follicle of Wave 1 prolonged its lifespan significantly, attaining the maximum diameter (Day 8.1+/-0.8) later than in untreated (Day 3.0+/-0.4) and nonpersisted follicle ewes (Day 2.0+/-0.6). The total number of follicles decreased in persistent follicle ewes between Day 0 and Day 4 (7.9+/-1.5 to 4.5+/-0.5, respectively; P< or =0.05) and remained low until the end of the experiment. Progesterone concentrations (nmol/L) between Days 6 and 9 were significantly different between untreated and persistent follicle ewes (12.8+/-1.0 vs. 9.4+/-1.0, P< or =0.02). The present study confirms that the largest follicle of Wave 1 is dominant in the ewe and that subluteal progesterone concentrations can prolong its lifespan and extend this dominance.     

Characterization of ovarian follicular wave dynamics in women

A wave phenomenon of ovarian follicular development in women has recently been documented in our laboratory. The objective of the present study was to characterize follicular waves to determine whether women exhibit major and minor wave patterns of follicle development during the interovulatory interval (IOI). The ovaries of 50 women with clinically normal menstrual cycles were examined daily using transvaginal ultrasonography for one IOI. Profiles of the diameters of all follicles >or=4 mm and the numbers of follicles >or=5 mm were graphed during the IOI. Major waves were defined as those in which one follicle grew to >or=10 mm and exceeded all other follicles by >or=2 mm. Minor waves were defined as those in which follicles developed to a diameter of <10 mm and follicle dominance was not manifest. Blood samples were drawn to measure serum concentrations of estradiol-17beta, LH, and FSH. Women exhibited major and minor patterns of follicular wave dynamics during the IOI. Of the 50 women evaluated, 29/34 women with two follicle waves (85.3%) exhibited a minor-major wave pattern of follicle development and 5 women (14.7%) exhibited a major-major wave pattern. Ten of the 16 women with three follicle waves (62.5%) exhibited a minor-minor-major wave pattern, 3 women (18.8%) exhibited a minor-major-major wave pattern, and 3 women (18.8%) exhibited a major-major-major wave pattern. Documentation of major and minor follicular waves during the menstrual cycle challenges the traditional theory that a single cohort of antral follicles grows only during the follicular phase of the menstrual cycle.     

Modification of follicular dynamics by exogenous FSH and progesterone, and the induction of ovulation using hCG in postpartum beef cows

Follicular growth and ovulation in response to FSH, progesterone and hCG were evaluated in postpartum beef cows. In Experiment 1, on Day 21 post partum, cows received an injection of either saline (control; n = 6), FSH (200 mg; n = 6), or a PRID (n = 5) for 10 d. Both FSH and PRID prolonged maintenance of a dominant follicle (15.5 +/- 1.16 and 14.4 +/- 1.29 d, respectively, vs 8.4 +/- 1.22 d in control; P < 0.01), and increased the maximum diameter of the dominant follicle (14.0 +/- 0.91 and 16.4 +/- 1.01 mm, respectively, vs 10.9 +/- 0.95 mm in control; P < 0.05). The PRID-maintained dominant follicle ovulated in 60% of cows, followed by normal estrous cycles (vs 0% in control; P = 0.01), whereas the dominant follicle ovulated in 33% of FSH-treated cows (P = 0.08). The PRID regimen shortened the interval to first ovulation preceding a normal cycle and continued cyclicity (44 +/- 4.1 vs 60 +/- 4.4 d in control; P = 0.02). In Experiment 2, on Day 21 post partum, cows received either saline (control), saline + PRID, or FSH + PRID (n = 16/group). Sixty hours after PRID withdrawal, cows received either saline or hCG (1,500 IU, n = 8/treatment). The FSH + PRID regimen increased the number of large (> 10 mm in diameter) follicles (3.6 +/- 0.43 vs 1.9 +/- 0.39 in control; P = 0.005). Both PRID and FSH + PRID prolonged maintenance of the largest follicle (11.0 +/- 0.82 and 11.2 +/- 0.91 d, respectively, vs 8.7 +/- 0.81 d in control; P < 0.05). The PRID-maintained dominant follicle ovulated in 50% of cows, followed by normal estrous cycles. The FSH + PRID-maintained largest follicle had become atretic at PRID withdrawal and was anovulatory. The FSH + PRID + hCG regimen increased the incidence of ovulation preceding a cycle of normal duration and continued cyclicity (100 vs 50% in PRID; P = 0.03), and reduced the interval to first ovulation preceding a cycle of normal duration and continued cyclicity (38 +/- 6.5 vs 58 +/- 6.3 d in control; P = 0.04). The area under the progesterone curve during the induced cycle was reduced after (PRID +/- FSH) + hCG than after PRID +/- FSH (P = 0.002). These results indicate that PRID alone or with FSH/hCG has the potential to modify the dominant follicle and initiate cyclicity in postpartum beef cows.     

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)     

Effect of eCG on early resumption of ovarian activity in postpartum dairy cows

The purpose of the present study was to hasten the resumption of ovarian activity early postpartum in lactating dairy cows, using equine chorionic gonadotropin (eCG), to enhance follicular growth, followed by hCG, to induce ovulation. Primiparous Holstein dairy cows (n=21) were assigned equally into eCG, eCG-hCG and Control groups. Cows in the eCG and eCG-hCG groups received an i.m. injection of eCG (500 IU Folligon?) on Day 6 postpartum. Cows in the eCG-hCG group were also given an i.m. injection of hCG (500 IU Chorulon?), once dominant follicle reached the diameter of 13-16 mm following eCG injection. Cows in Control group did not receive any treatment. Daily blood sampling and ultrasound examination were conducted, starting at Day 6 postpartum until confirming the third ovulation. Follicles ≥10 mm in diameter were detected on Day 11.5±1.48, 10.1±0.52 and 11.1±1.36 after calving in Control, eCG and eCG-hCG groups, respectively (P>0.05). The first wave dominant follicle ovulated in 71.4% of cows treated with eCG and eCG-hCG. In contrast, none of the first wave dominant follicles ovulated in Control cows. By Day 20 postpartum, all cows in eCG group, 6/7 cows in eCG-hCG group and none of the cows in Control group ovulated (P<0.05). Short estrous cycles (≤16 days) were detected in 2/7, 1/7 and 6/7 cows in eCG, eCG-hCG and control groups, respectively (P<0.05). In conclusion, injection of eCG on Day 6 postpartum could assist the early resumption of ovarian activity by enhancing ovarian follicle growth and early ovulation in postpartum cows. In this context, subsequent hCG injection may not provide any more beneficial effect.     

Animal and temporal effects on ovarian follicular dynamics in Brahman heifers

The aims of the current study were to determine if the pattern of ovarian follicular growth and development in Bos indicus heifers is different to that reported in Bos taurus breeds, and to examine the factors that determine which dominant follicle will ovulate. In addition, the extent to which variation in follicular dynamics is attributable to variation between animals and over time was evaluated. The ovaries of 17 Brahman heifers were examined daily by transrectal ultrasonography using a 7.5 MHz transducer for a total of 117 interovulatory intervals over a period of 10 months. Size and position of individual follicles ⪖5 mm in diameter, and size of corpora lutea (CL) were recorded. Circulating progesterone concentrations were determined from plasma samples obtained twice weekly. Although size of dominant follicles and CL within the ovaries of Bos indicus heifers were smaller than reported for Bos taurus breeds, the overall patterns of dominant follicle growth were similar. There were significant correlations between number of dominant follicles occurring prior to ovulation and time of appearance of the second dominant follicle, duration of detection of CL and size of the ovulatory follicle in the preceding oestrous cycle (P < 0.05). There were significant animal effects on a number of ovarian characteristics including number of dominant follicles per oestrous cycle (P < 0.001), with one heifer having four dominant follicles in more than a third of oestrous cycles observed. In addition, changes in daylength over the 10 month period were related to changes in duration of the interovulatory interval, persistence and maximum diameter of CL and size of ovulatory follicles. Liveweight change over the same period was related to changes in maximum diameter of the first dominant follicle.