Changes in ovarian follicular dynamics and luteinizing hormone profiles following different progestagen treatments in cattle

1994 ◽  
Vol 74 (2) ◽  
pp. 273-279 ◽  
Author(s):  
C. Taylor ◽  
M. Manikkam ◽  
R. Rajamahendran
Keyword(s):  
Luteinizing Hormone ◽  
Key Words ◽  
Pulse Frequency ◽  
Implant Removal ◽  
Dominant Follicle ◽  
Blood Samples ◽  
Treatment Groups ◽  
Lactating Cows ◽  
Intravaginal Device ◽  
Follicular Dynamics

Twelve cyclic non-lactating cows were allocated at random to three treatment groups (IN, NP and 2N). Cows in the 1N group (n = 4) received an ear implant containing Norgestomet at pro-estrus (day 0 = day of Norgestomet-implant insertion). Cows in the NP group (n = 4) received a progesterone-releasing intravaginal device 3 d after a Norgestomet implant at pro-estrus, and cows in the 2N group (n = 4) received a second Norgestomet implant 3 d after the first implant at pro-estrus. Treatments were terminated on day 9. Ultrasonic examination of the ovaries was carried out before, during and after treatment to monitor follicular dynamics. Serial blood samples were collected every 15 min for 8 h from all cows on days 3 and 6 after initiation of treatments to characterize the luteinizing hormone (LH) profiles. The dominant follicle was maintained for 9 d in all IN cows, and upon implant removal all cows ovulated. In both NP and 2N cows, the dominant follicle regressed and a new cohort of small follicles appeared before the end of the treatment. The dominant follicle from this pool ovulated after implant removal in all NP cows. In the 2N group, only one cow ovulated after implant removal; the dominant follicles in the remainder became cystic and did not ovulate. Decreases in pulse frequency, amplitude and mean plasma LH were observed in the NP cows, compared with IN cows (P < 0.05), but no change in LH-pulse frequency was observed in the 2N cows. This study shows clearly that maintenance and regression of the dominant follicle are associated with changes in progesterone and LH environment. Key words: Progestin, dominant follicle, ultrasound, regression, luteinizing hormone, cattle

Effects of oestradiol and progesterone on pulsatile secretion of luteinizing hormone in ovariectomized ewes

1986 ◽  
Vol 111 (2) ◽  
pp. 172-178 ◽  
Author(s):  
C. Tamanini ◽  
M. E. Crowder ◽  
T. M. Nett
Keyword(s):  
Luteinizing Hormone ◽  
Treatment Period ◽  
Sampling Period ◽  
Inhibitory Effect ◽  
Blood Samples ◽  
Pulsatile Release ◽  
Treatment Groups ◽  
Effect Of Treatment ◽  
Gonadotrophin Releasing Hormone ◽  
Cessation Of Treatment

Abstract. The effect of treatment with oestradiol, progesterone, a combination of the two steroids or no steroids on pulsatile release of luteinizing hormone (LH) was examined in ovariectomized ewes. Beginning 3 days after ovariectomy, 5 ewes were assigned to each of the following treatment groups: 0.7 mg oestradiol, 16 mg progesterone, 0.7 mg oestradiol plus 16 mg progesterone or no steroid. All treatments were administered twice daily for 3 weeks in a 0.5 ml injection of ethanol given sc. After 2 weeks of treatment and 1, 4, 8, 16 and 32 days after the treatment period ended, blood samples were obtained from all ewes at 10-min intervals for a 6-h period. At the end of the 6-h period, 100 μg gonadotrophin-releasing hormone (GnRH) was injected iv and blood samples were collected at 15 min intervals for an additional 5 h to estimate the relative pituitary content of LH. Ovariectomized ewes receiving no steroid presented regular pulses of LH at frequency of four to five pulses during a 6-h sampling period. Treatment with progesterone alone decreased the frequency of pulsatile release of LH to approximately 1 pulse/6 h, but did not affect the amplitudes of the pulses of LH. Recovery of pulsatile release of LH to a frequency of four or five pulses of LH in a 6-h period was complete between 16 and 32 days after treatment ended in progesterone-treated ewes. Oestradiol, administered alone or with progesterone, resulted in a decrease in both the frequency and the amplitude of pulses of LH compared to control ewes and a decrease in GnRH-induced release of LH. In these groups, the GnRH-induced release of LH had returned to normal by 32 days after cessation of treatment. Although frequency and amplitude of endogenous pulses had increased by 32 days post-treatment, neither parameter had returned to normal. These data suggest that oestradiol exerts an inhibitory effect on the pituitary by decreasing the content of LH to a level which precludes pulsatile release of LH. Progesterone, in contrast, may inhibit the frequency of release of pulses of LH by reducing the frequency of pulsatile release of GnRH from the hypothalamus.

Abnormal patterns of ovarian activity in dairy cows and their relationships with reproductive performance

1980 ◽  
Vol 30 (2) ◽  
pp. 177-188 ◽  
Author(s):  
D. Claire Bulman ◽  
P. D. P. Wood
Keyword(s):  
Luteinizing Hormone ◽  
Dairy Cows ◽  
Reproductive Performance ◽  
Profile Analysis ◽  
Single Injection ◽  
Ovarian Activity ◽  
Luteinizing Hormone Releasing Hormone ◽  
Treatment Groups ◽  
Intravaginal Device ◽  
Ovarian Cycles

ABSTRACTProgesterone profiles were obtained from 533 dairy cows during the interval from calving to the re-establishment of pregnancy by twiceweekly radioimmunoassay of milk progesterone. The importance of abnormal patterns of ovarian activity on herd fertility was determined. Animals were divided into five categories based on profile analysis: A, normal; B, delayed start to ovarian cycles; C, cessation of cycles; D, prolonged luteal activity; and E, silent oestrus. Animals in categories B to E were subdivided into treatment groups: categories B and C either (i) untreated controls, (ii) single injection 0·5 mg luteinizing hormone-releasing hormone (Hoechst) or (iii) progesterone-releasing intravaginal device (Abbott Laboratories Ltd) inserted for 14 days; categories D and E either (i) untreated controls or (ii) single injection 0-5 mg cloprostenol (Imperial Chemical Industries).The proportion of cows in each category was: A 77·5%; B 4·9%; C 5·1%; D 1·9%; and E 10·7%. The incidence of ‘normal’ cows was 75% (first lactation), 80% (2nd to 5th lactations) and 69% (5th to 11th lactations). For normal cows (no. = 413) the interval to the start of cyclicity varied significantly with season but was not correlated with either the intervals to first insemination or to conception. In categories B to E the open period, the number of services per conception, and the days from first insemination to conception were greater than in category A, but only in category C were any differences significant. None of the treatments reduced calving-toconception intervals.

THE INFLUENCE OF GILT AGE ON THE ENDOCRINE AND OVULATORY RESPONSE TO DIFFERENT DOSES OF ESTRADIOL BENZOATE

1988 ◽  
Vol 68 (3) ◽  
pp. 979-982 ◽  
Author(s):  
R. N. KIRKWOOD ◽  
F. X. AHERNE
Keyword(s):  
Body Weight ◽  
Luteinizing Hormone ◽  
Key Words ◽  
Jugular Vein ◽  
Estradiol Benzoate ◽  
Blood Samples ◽  
Estrous Cyclicity ◽  
The Mean ◽  
Different Doses ◽  
Phasic Release

Fifty-five prepubertal Yorkshire × Landrace gilts were randomly assigned to one of six treatments involving the injection (i.m.) of estradiol benzoate (EB) at either 10 or 20 μg kg−1 body weight at gilt ages of 130, 150 or 170 d. Blood samples were taken by jugular vein puncture at 0, 24, and 36 h, and then at 6-h intervals until 84 h, after injection and assayed for plasma luteinizing hormone (LH) concentrations. The mean magnitude of the EB-induced LH peak was 6.1 ± 0.2 ng mL−1, and was not affected by treatment. Fifty-six percent of gilts ovulated in response to EB injection, and 34% had a subsequent ovulation. The initial ovulation rate was unaffected by EB dose, but was higher (P < 0.05) in 170 d (9.9 ± 1.0) compared to younger gilts (4.2 ± 1.1 and 5.5 ± 1.1 for 130-dand 150-d gilts, respectively). Subsequent ovulation rates were unaffected by treatment. It is concluded that EB treatment will usually induce a phasic release of LH from prepubertal gilts, but this release is not necessarily accompanied by normal estrous cyclicity. Key words: Estradiol, gilts, ovulation

Ovarian responses of anestrous ewes to the "ram effect"

2002 ◽  
Vol 82 (4) ◽  
pp. 599-602 ◽  
Author(s):  
R. Ungerfeld ◽  
A. Pinczak ◽  
M. Forsberg ◽  
E. Rubianes
Keyword(s):  
Luteinizing Hormone ◽  
Key Words ◽  
Luteal Phase ◽  
Follicle Stimulating Hormone ◽  
Lh Surge ◽  
Follicular Cyst ◽  
Ram Effect ◽  
Ovulatory Follicles ◽  
Follicular Dynamics ◽  
Stimulating Hormone

Ovarian responses to the "ram effect" were characterized in 11 anestrous Corriedale ewes. In seven ewes, there was a luteinizing hormone (LH) surge 36.7 ± 12.3 h (mean ± SEM) after ram introduction and a concurrent increase (P < 0.05) in serum follicle stimulating hormone (FSH). Ovarian responses (monitored ultrasonographically) were highly variable. One ewe had two luteal phases (short and normal, respectively), three had delayed ovulation (days 5–7), two had luteinization of non-ovulatory follicles, one developed a luteinized follicular cyst, and four had no luteal phase. Key words: Ram effect, ovarian follicular dynamics, seasonal anestrus, ultrasonography, gonadotropin

Regulation of LH secretion during seasonal anestrus by dopaminergic pathways in Rasa Aragonesa ewes treated or not with melatonin

2003 ◽  
Vol 83 (2) ◽  
pp. 311-313 ◽  
Author(s):  
F. Forcada ◽  
J. A. Abecia ◽  
O. Zúñiga
Keyword(s):  
Luteinizing Hormone ◽  
Key Words ◽  
Dopaminergic System ◽  
Pulse Frequency ◽  
Steroid Dependent ◽  
Dependent Inhibition ◽  
And Control ◽  
Lh Secretion ◽  
Dopaminergic Pathways

The involvement of the dopaminergic system in the steroid-dependent inhibition of luteinizing hormone (LH) secretion during anestrus in ovariectomized, estradiol-implanted adult Rasa Aragonesa ewes was investigated in both ewes treated with melatonin on 8 March (n = 10) and in control (n = 8) ewes. Melatonin implants did not significantly increase LH secretion. However, treatment with pimozide induced a significant increase (P < 0.05) in LH pulse frequency in both groups during early anestrus. We conclude that, in the absence of males, the dopaminergic system is clearly involved in the inhibition of LH secretion during anestrus in both melatonin-treated and control ewes. Key words: Sheep, melatonin, pimozide

Effect of mid-luteal phase progesterone levels on the first wave dominant follicle in cattle

1994 ◽  
Vol 74 (2) ◽  
pp. 281-285 ◽  
Author(s):  
C. Taylor ◽  
R. Rajamahendran
Keyword(s):  
Key Words ◽  
Estrous Cycle ◽  
Luteal Phase ◽  
Follicular Growth ◽  
Dominant Follicle ◽  
Prostaglandin F ◽  
Follicular Dynamics

A wave-like-pattern of follicular growth and regression during the luteal phase has been described in the bovine. The factors responsible for inducing the onset of regression of nonovulatory dominant follicles are unknown. The present study was designed to examine the effect of progesterone (P4) administration early in the estrous cycle on the first wave dominant follicle. Nine heifers were administered P4 on day 3 (200 mg), day 4 (100 mg) and day 5 (50 mg) of the estrous cycle (Day 0 = day of estrus) and seven heifers received vehicle to serve as controls. All heifers received a luteolytic dose of prostaglandin F2α (PGF2α) on day 7. Follicular dynamics were monitored by daily ultrasonography. All seven control heifers ovulated the first wave dominant follicle. In four P4 treated heifers, the first wave dominant follicle regressed prior to PGF2α administration and a dominant follicle from the second pool of follicles ovulated. The remaining five P4 treated heifers ovulated the first wave dominant follicle. However, in these heifers the growth of the first wave dominant follicle was slower (0.65 ± 0.13 mm day−1 between days 3 to 7 for treated vs 1.46 ± 0.23 mm day−1 for control; P < 0.05) and estrus and ovulation were delayed compared to controls (3.8 ± 0.3 vs 2.4 ± 0.2 and 5.2 ± 0.4 vs 3.9 ± 0.2 days after PGF2α, respectively; P < 0.05). The results indicate that P4 administered early in the estrous cycle to mimic the mid luteal phase levels alters follicular dynamics and is capable of inducing premature regression of the first wave dominant follicle. Key words: Progesterone, dominant follicle, cattle, atresia, ovulation

Ovarian follicular dynamics and concentrations of oestradiol-17 beta, progesterone, luteinizing hormone and follicle stimulating hormone during the periovulatory phase of the oestrous cycle in the cow

1991 ◽  
Vol 3 (5) ◽  
pp. 529 ◽  
Author(s):  
H Kaneko ◽  
T Terada ◽  
K Taya ◽  
G Watanabe ◽  
S Sasamoto ◽  
...  
Keyword(s):  
Plasma Concentration ◽  
Luteinizing Hormone ◽  
Follicle Stimulating Hormone ◽  
Follicular Phase ◽  
Corpora Lutea ◽  
Dominant Follicle ◽  
Follicular Wave ◽  
Ovulatory Follicle ◽  
Follicular Dynamics ◽  
Stimulating Hormone

Changes in the plasma concentration of oestradiol-17 beta, progesterone, luteinizing hormone (LH) and follicle stimulating hormone (FSH) were characterized during the transition from the luteal to the follicular phase, the periovulatory period and the early luteal phase in five cycling cows. The pattern of growth and the regression of follicles and corpora lutea in the ovary of the same animals were also assessed by daily ultrasonographic examinations. Two waves of follicular growth (ovulatory and non-ovulatory) occurred in all animals. The ovulatory follicular wave started from 4 days before the preovulatory surges of LH and FSH and the wave of next growth of a dominant follicle (non-ovulatory follicle) started within one day after ovulation. Changes in plasma levels of oestradiol-17 beta correlated well with the growth of both ovulatory and non-ovulatory dominant follicles. Suppression of FSH concentration during the follicular phase was inversely related to the increase in plasma concentration of oestradiol-17 beta. These results suggest that, in the cow, ovulatory dominant follicles suppress FSH secretion by increasing the concentration of oestradiol-17 beta (and probably also inhibin) during the follicular phase.

Effects of bromocriptine administration during the follicular phase of the oestrous cycle on prolactin and gonadotrophin secretion and follicular dynamics in merino monovular ewes

Reproduction ◽  
2000 ◽  
pp. 177-186 ◽  
Author(s):  
RA Picazo ◽  
A Gonzalez De Bulnes ◽  
A Gomez Brunet ◽  
A del Campo ◽  
B Granados ◽  
...  
Keyword(s):  
Pulse Frequency ◽  
Prolactin Secretion ◽  
Follicular Phase ◽  
Oestrous Cycle ◽  
Control Group ◽  
Blood Samples ◽  
Vehicle Injection ◽  
Group 2 ◽  
Time Point ◽  
Follicular Dynamics

Two experiments using Spanish Merino ewes were conducted to investigate whether the secretion of prolactin during the follicular phase of the sheep oestrous cycle was involved in the patterns of growth and regression of follicle populations. In both experiments, oestrus was synchronized with two cloprostenol injections which were administered 10 days apart. Concurrent with the second injection (time 0), ewes (n = 6 per group) received one of the following treatments every 12 h from time 0 to 72 h: group 1: vehicle injection (control); group 2: 0.6 mg bromocriptine (0.03 mg per kg per day); and group 3: 1.2 mg bromocriptine (0.06 mg per kg per day). In Expt 1, blood samples were collected every 3 h from 0 to 72 h, and also every 20 min from 38 to 54 h to measure prolactin, LH and FSH concentrations. In Expt 2, transrectal ultrasonography was carried out every 12 h from time 0 until oestrus, and blood samples were collected every 4 h to measure prolactin, LH and FSH concentrations. Ovulation rates were determined by laparoscopy on day 4 after oestrus. Bromocriptine markedly decreased prolactin secretion, but did not affect FSH concentrations, the mean time of the LH preovulatory surge or LH concentrations in the preovulatory surge. Both doses of bromocriptine caused a similar decrease in LH pulse frequency before the preovulatory surge. The highest bromocriptine dose led to a reduction (P < 0.01) in the number of 2-3 mm follicles detected in the ovaries at each time point. However, bromocriptine did not modify the total number or the number of newly detected 4-5 mm follicles at each time point, the number of follicles > 5 mm or the ovulation rate. In conclusion, the effects of bromocriptine on gonadotrophin and prolactin secretion and on the follicular dynamics during the follicular phase of the sheep oestrous cycle indicate that prolactin may influence the viability of gonadotrophin-responsive follicles shortly after luteolysis.

Effect of exogenous LH pulses on the fate of the first dominant follicle in postpartum beef cows nursing calves

Reproduction ◽  
2000 ◽  
pp. 9-17 ◽  
Author(s):  
P Duffy ◽  
MA Crowe ◽  
MP Boland ◽  
JF Roche
Keyword(s):  
Postpartum Period ◽  
Maximum Size ◽  
Beef Cows ◽  
Pulse Frequency ◽  
New Wave ◽  
Dominant Follicle ◽  
Blood Samples ◽  
Lh Surge ◽  
Early Postpartum Period ◽  
Early Postpartum

Prolonged postpartum anoestrus in beef cows is due to failure of early dominant follicles to ovulate. It is hypothesized that this failure to ovulate is due to inadequate LH pulse frequency. The objective of this study was to determine whether administration of hourly LH pulses would cause the first dominant follicle to ovulate. In Expt 1, 16 cows received either saline (n = 8) or porcine LH (pLH; 50 micrograms h-1; n = 8) as hourly pulses for 3-5 days from the second day of dominance of the first dominant follicle (day 0). In Expt 2, 21 cows received either saline (n = 7), or 50 micrograms pLH (n = 7) or 100 micrograms pLH (n = 7) as hourly pulses for 3 days. Appropriate ovarian scanning and assays of blood samples were carried out. In Expt 1, the number of dominant follicles that underwent atresia was not affected by increasing the number of LH pulses, but the duration of dominance (days) of the first and second dominant follicles and maximum size (mm) of the second dominant follicle were increased (P < 0.05). Oestradiol concentrations were higher (P < 0.05) in cows given hourly pLH pulses (3.1 +/- 1.2 pg ml-1) compared with controls (1.2 +/- 0.2 pg ml-1). Four of eight treated cows had an anovulatory LH surge. The number of follicle waves to first ovulation was not different (P < 0.05) between control (4.6 +/- 0.9) and pLH treated cows (3.9 +/- 0.5). In Expt 2, four of seven cows given pulses of 100 micrograms pLH h-1 ovulated the first dominant follicle, and the interval from calving to first ovulation was decreased (P < 0.05). In the remaining three cows, the duration of dominance of the first dominant follicle was increased (P < 0.005), the maximum size of the first dominant follicle was greater (P < 0.05), and the interval (days) from the start of infusion to new wave emergence was greater (P < 0.05) compared with cows that failed to ovulate in either the 50 micrograms pLH h-1 or control treatments. In conclusion, hourly pulses of pLH from day 1 after dominance of the first dominant follicle in postpartum beef cows can either prolong dominance or induce it to ovulate. This finding supports the hypothesis that LH pulse frequency is a key determinant of the fate of the dominant follicle in the early postpartum period.

The effects of acclimation to confinement on gonadotrophin and cortisol secretion during the estrous cycle of the ewe

1991 ◽  
Vol 71 (2) ◽  
pp. 327-332 ◽  
Author(s):  
N. C. Rawlings ◽  
S. J. Cook
Keyword(s):  
Key Words ◽  
Estrous Cycle ◽  
Pulse Amplitude ◽  
Pulse Frequency ◽  
Cortisol Secretion ◽  
Serum Concentrations ◽  
Blood Samples ◽  
Progesterone Secretion ◽  
Serum Lh ◽  
Lh Secretion

The purpose of the study was to examine the effects of acclimation to confined housing on tonic gonadotrophin, cortisol and progesterone secretion in ewes at different stages of the estrous cycle. On days 4, 12 and 16 of the estrous cycle separate groups of eight ewes were blood sampled every 5 min for 6 h. Of the eight ewes bled at each stage of the cycle four were moved from outside drylots to small pens in a building 2 d prior to blood sampling and four were moved 4 d prior to sampling. All blood samples were analyzed for concentrations of LH and FSH and one sample for each hour of intensive bleeding, for each ewe, was analyzed for cortisol and progesterone. All hormone concentrations were obtained by radioimmunoassay. On day 4 of the estrous cycle LH pulse frequency and mean serum concentrations of LH were higher, but mean FSH concentrations were lower, in ewes confined for 4 d, compared to those confined for 2 d (P < 0.05). On day 12 of the cycle, mean serum LH concentrations only were higher in ewes confined for 4 d (P < 0.05). At day 16 no differences were seen between ewes confined for 2 or 4 d. Serum concentrations of progesterone, cortisol and LH pulse amplitude did not vary significantly between ewes confined for 2 or 4 d. However, in ewes confined for 4 d, serum concentrations of cortisol fell from day 4 to day 16 of the estrous cycle (P < 0.05). We conclude that acclimation to confined housing in the intact cyclic ewe is reflected in changes in tonic LH secretion at stages of the estrous cycle when serum concentrations of cortisol are high. Key words: LH, FSH, cortisol, confinement, cyclic ewe

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