Comparisons between peripheral progesterone concentrations in cyclic and pregnant Landrace x large White and Meishan gilts

1994 ◽  
Vol 6 (6) ◽  
pp. 777 ◽  
Author(s):  
CJ Ashworth ◽  
AW Ross ◽  
CS Haley
Keyword(s):  
Luteal Phase ◽  
Oestrous Cycle ◽  
Ovulation Rate ◽  
Large White ◽  
Blood Samples ◽  
Breed Differences

Progesterone concentrations were determined in blood samples collected twice daily (at 0900 and 1700 hours) from the day of oestrus (Day 0) until Days 15-24 in ten Landrace x Large White gilts (four cyclic and six pregnant gilts) and eight Meishan gilts (four cyclic and four pregnant gilts). Progesterone concentrations during the early luteal phase tended to be higher in pregnant Meishan gilts than in pregnant Landrace x Large White gilts. Furthermore, when differences in ovulation rate and peak progesterone concentrations were accounted for, maximum progesterone concentrations occurred earlier in Meishan gilts than in Landrace x Large White gilts (P < 0.01); this difference was particularly marked when pregnant animals of the two breeds were compared. In non-mated animals, analyses of the timing and magnitude of progesterone concentrations observed towards the end of the oestrous cycle revealed that the decrease in progesterone concentrations occurred earlier (P < 0.05) in Meishan gilts. Such breed differences in the peripheral progesterone profile may be associated with reduced prenatal mortality, a characteristic of Meishan females.

Passively immunizing ewes against inhibin during the luteal phase of the oestrous cycle raises the plasma concentration of FSH

1989 ◽  
Vol 123 (3) ◽  
pp. 383-391 ◽  
Author(s):  
G. E. Mann ◽  
B. K. Campbell ◽  
A. S. McNeilly ◽  
D. T. Baird
Keyword(s):  
Plasma Concentration ◽  
Luteal Phase ◽  
Passive Immunization ◽  
Oestrous Cycle ◽  
Ovulation Rate ◽  
Control Group ◽  
Pituitary Cells ◽  
Marked Rise ◽  
Peripheral Plasma

ABSTRACT Passive immunization was used to investigate the importance of inhibin in the negative feedback loop regulating the production of FSH in sheep. An antiserum raised to the 1–26 peptide fragment of the N-terminus of the α-chain of porcine inhibin was first shown to neutralize the suppressive effects of inhibin on the production of FSH by dispersed ovine pituitary cells in vitro. Groups of five mature Scottish Blackface ewes on day 8 of the luteal phase of the oestrous cycle were then injected with either 10 ml plasma from normal ewes (control) or 10 ml ovine inhibin antiserum. On day 10, luteal regression was induced by an i.m. injection of cloprostenol (100 μg), and ovulation rate determined 6 days later by laparoscopy. Peripheral plasma samples were collected throughout the experimental period. Following treatment, there was no change in the peripheral plasma concentration of LH in either group. Following injection of the inhibin antiserum, the concentration of FSH rose significantly (P<0·001) compared with the control group. The concentration of FSH rose from 1·42 ± 0·06 to a maximum of 2·58 ± 0·23 (s.e.m.) μg/l by 5·6 ±0·9 h, this maximum lasting 9·0±1·1 h. By 32·8 ±6·9 h, the concentration of FSH had returned to pretreatment levels, while the titre of free antibody in the plasma of treated ewes was still high. In the treated ewes, there were one single and four double ovulations compared with three single and two double ovulations in the control group, indicating that the inhibin immunization may have resulted in an increase in ovulation rate. We conclude that the marked rise in the plasma concentration of FSH following injection of inhibin antiserum provides strong evidence that inhibin is an important factor in the regulation of FSH production by the pituitary gland at this time. Journal of Endocrinology (1989) 123, 383–391

PERIPHERAL PLASMA PROGESTERONE CONCENTRATIONS IN SHEEP DURING THE OESTROUS CYCLE

1973 ◽  
Vol 58 (2) ◽  
pp. 219-225 ◽  
Author(s):  
K. P. McNATTY ◽  
K. J. A. REVFEIM ◽  
A. YOUNG
Keyword(s):  
Luteal Phase ◽  
Oestrous Cycle ◽  
Diurnal Changes ◽  
Progesterone Concentration ◽  
Once Daily ◽  
Plasma Progesterone ◽  
Blood Samples ◽  
Peripheral Plasma ◽  
The Hours

SUMMARY Progesterone concentrations in peripheral plasma were measured once daily during one oestrous cycle in each of eight sheep. In addition, on days 4–5, 8–9, 12–13 and 15–16 of the oestrous cycle, blood samples were collected at 30-min intervals throughout each 24-h period. A total of three ewes was sampled in each 24-h period and the same three animals were not bled again for at least 1 week. Plasma progesterone concentrations in all the ewes fluctuated considerably throughout each 24-h period. The within-sheep within-day variations observed in peripheral progesterone concentrations were compared with the between-sheep within-day variations and the within-sheep between-day variations previously reported. It is concluded that these previously reported variations in peripheral plasma progesterone concentration could be attributed to within-day variations in each animal. On days 8–9 and 12–13 of the oestrous cycle there were significantly higher concentrations of progesterone in plasma during the hours of daylight than during the hours of darkness. In contrast, progesterone concentrations on days 4–5 and 15–16 were not found to be significantly different between the hours of daylight and darkness. These results suggest that diurnal changes in peripheral plasma progesterone concentration occur during the luteal phase of the ovine oestrous cycle.

Pulsatile secretion of inhibin, oestradiol and androstenedione by the ovary of the sheep during the oestrous cycle

1990 ◽  
Vol 126 (3) ◽  
pp. 385-393 ◽  
Author(s):  
B. K. Campbell ◽  
G. E. Mann ◽  
A. S. McNeilly ◽  
D. T. Baird
Keyword(s):  
Luteal Phase ◽  
Venous Blood ◽  
Pulse Amplitude ◽  
Pulse Frequency ◽  
Follicular Phase ◽  
Oestrous Cycle ◽  
Blood Samples ◽  
Early Follicular Phase ◽  
Lh Secretion ◽  
Late Follicular Phase

ABSTRACT The pattern of pulsatile secretion of inhibin, oestradiol and androstenedione by the ovary at different stages of the oestrous cycle in sheep was studied in five Finn–Merino ewes in which the left ovary had been autotransplanted to the neck. The ewes had jugular venous blood samples collected at 4-hourly intervals from 42 h before the induction of luteolysis by i.m. injection of cloprostenol (100 μg) on day 10 of the oestrous cycle, until day 3 of the following cycle. There were five periods of intensive blood sampling, when both ovarian and jugular venous blood samples were collected, as follows: (a) mid-luteal phase, before the second injection of cloprostenol on day 10 (15-min intervals for 6 h); (b) early follicular phase, 24 h after the second injection of cloprostenol (10-min intervals for 4 h); (c) late follicular phase, 48 h after the second injection of cloprostenol (10-min intervals for 4 h); (d) after the LH surge on day 1 of the cycle, 76 h after the second injection of cloprostenol (10-min intervals for 4 h); (e) early luteal phase on day 3 of the cycle, 120 h after the second injection of cloprostenol (10-min intervals for 3 h). Plasma was collected and the samples assayed for LH, FSH, progesterone, oestradiol, androstenedione and inhibin. The ovarian secretion rates for oestradiol, androstenedione and inhibin were calculated. All ewes responded normally to the luteolytic dose of cloprostenol with the preovulatory surge of LH occurring within 56·4±1·6 h (mean ± s.e.m.) followed by the establishment of a normal luteal phase. The pulse frequency of LH, oestradiol and androstenedione increased in the transition from the luteal to the follicular phase (P<0·01). On day 1 of the cycle LH secretion consisted of low-amplitude high-frequency pulses (1·0±0·1 pulse/h) to which androstenedione, but not oestradiol, responded. On day 3 of the cycle LH secretion was similar to that on day 1 but both androstenedione and oestradiol secretion were pulsatile in response to LH, indicating the presence of oestrogenic follicles. The stage of the cycle had no significant effects on LH pulse amplitude and nadir but the ovarian secretory response to LH stimulation did vary with the stage of the cycle. Prolactin pulse frequency, amplitude and nadir were higher (P<0·05) during the follicular phase than the luteal phase. Prolactin pulse frequency was depressed (P<0·05) on day 1 of the cycle but increased to follicular phase levels on day 3. Prolactin pulse frequency was significantly correlated to oestradiol pulse frequency (r = 0·54; P<0·01). During the luteal phase there were insufficient oestradiol pulses to obtain an estimate of pulse amplitude and nadir but both these parameters reached their highest level during the late follicular phase, fell to negligible levels on day 1 and increased to early follicular phase levels on day 3. Androstenedione pulse amplitude and nadir exhibited similar but less marked variation. Inhibin secretion was episodic at all stages of the cycle examined but did not exhibit significant variation with stage of cycle in any of the parameters of episodic secretion measured. Inhibin pulses were not related to either LH or prolactin at any stage of the cycle. FSH secretion was not detectably pulsatile but jugular venous concentrations of FSH at each stage of the oestrous cycle were negatively correlated with mean oestradiol (r= −0·52; P<0·01 but not inhibin secretion (r = 0·19). We conclude that (i) LH secretion is pulsatile at all stages of the oestrous cycle but the steroidogenic responses of the ovary varies with the stage of the cycle, reflecting changes in characteristics of the follicle population, (ii) ovarian inhibin secretion is episodic and displays little change with the stage of the oestrous cycle and (iii) episodic inhibin secretion is not related to either pulses of LH or prolactin. The aetiology of these inhibin pulses therefore remains unknown. Journal of Endocrinology (1990) 126, 385–393

Naloxone evokes a nutritionally dependent LH response in post partum beef cows but not in mid-luteal phase maiden heifers

1995 ◽  
Vol 61 (2) ◽  
pp. 219-230 ◽  
Author(s):  
K. D. Sinclair ◽  
P. J. Broadbent ◽  
J. S. M. Hutchinson
Keyword(s):  
Energy Intake ◽  
Body Condition ◽  
Luteal Phase ◽  
Dry Matter ◽  
Post Partum ◽  
Beef Cows ◽  
High Energy ◽  
Oestrous Cycle ◽  
Blood Samples ◽  
Post Partum Period

AbstractData from two experiments are reported which test the hypothesis that nutrient and/or dry-matter intake and body condition may interact to modify hypothalamic opioidergic activity and thus influence the pulsatile release of LH during the early post-partum period and during the oestrous cycle. Experiment 1 involved 16 multiparous, twin-suckling beef cows, and was a 2 × 2 × 2 factorial design in which the factors were level of post-partum energy intake (80 v. 130 M) metabolizable energy (ME) per day), the digestible undegradable protein (DUP) content of the post-partum diet (14 v. 31 g/kg dry matter), and treatment with either 200 mg or 400 mg naloxone hydrochloride. Blood samples were collected at 15-min intervals for 4h at weeks 4 and 7 post partum. Naloxone was administered intravenously after the eighth sample. Experiment 2 involved 16 cyclic maiden heifers and was also arranged in a factorial manner, with two levels of body condition at the start of the experimental period (2·50 and 3·16 units) and two levels of energy intake thereafter (40 and 80 MJ ME per day). Seven blood samples were collected at 15-min intervals on 4 days consecutively during the mid-luteal phase of the oestrous cycle. On the first 2 of these 4 days naloxone was administered, whilst on the last 2 days a gonadotropin-releasing hormone agonist (buserelin; GnRH) was administered, both after the fourth sample. Plasma from both experiments was assayed for LH and prolactin (Prl).In experiment 1, cows on 130 MJ ME per day returned to oestrus and ovulated earlier than cows on 80 MJ ME per day (44·5 v. 55·0 days; s.e.d. = 3·93; P < 0·05). At week 4 post partum the proportional increase in plasma LH following naloxone challenge was greater for cows on 130 MJ ME per day than cows on 80 MJ ME per day (1·38 v. 1·12; P < 0·05), but the converse was true at week 7 (1·15 v. 1·68; P < 0·05). Cows on the high DUP diet required a higher dose of naloxone to elicit an LH response. Few heifers in experiment 2 exhibited an LH response to naloxone. In contrast, there were significant dietary treatment effects on the LH response to GnRH (P < 0·01). Relatively thin heifers on 40 MJ ME per day exhibited the lowest proportional increases in plasma LH to GnRH challenge, whereas heifers on 80 MJ ME per day and given the higher dose of GnRH produced the greatest plasma LH responses. Mean Prl concentrations before and after feeding in experiment 2 were respectively 13·2 and 10·2 ng/l (P < 0·01).Suckled cows given a high energy diet during the early post-partum period can overcome the opioid mediated block on LH release and resume oestrous cycles earlier than cows given a low energy diet. LH would appear to be inhibited by a non-opioid mechanism in mid-luteal phase heifers. Total pituitary reserves ofLH may be influenced by the animals nutritional status.

Changes in the secretion of LH pulses, FSH and prolactin during the preovulatory phase of the oestrous cycle of the ewe and the influence of treatment with bovine follicular fluid during the luteal phase

1988 ◽  
Vol 116 (1) ◽  
pp. 123-135 ◽  
Author(s):  
J. M. Wallace ◽  
G. B. Martin ◽  
A. S. McNeilly
Keyword(s):  
Follicular Fluid ◽  
Luteal Phase ◽  
Pulse Amplitude ◽  
Pulse Frequency ◽  
Ovarian Follicles ◽  
Follicular Phase ◽  
Oestrous Cycle ◽  
Ovulation Rate ◽  
The Other ◽  
Lh Secretion

ABSTRACT It has previously been shown that treatment of ewes with bovine follicular fluid (bFF) throughout the luteal phase of the oestrous cycle lowers plasma levels of FSH but increases the frequency and amplitude of the pulses of LH. Under these conditions, ovarian follicles grow to a maximum diameter of 2·7 mm and have a reduced capacity to release oestradiol. We have examined the nature of the gonadotrophin signals controlling follicular development in the normally cycling ewe and have investigated the effects of previous exposure to bFF on these signals and the follicular responses to them. Control ewes (n = l) were injected i.v. with 9 ml bovine serum and treated ewes were injected with 9 ml bFF, twice daily from days 1 to 10 of the luteal phase (day 0 = oestrus). The ewes were injected with prostaglandin analogue on day 11 of the cycle to induce luteolysis and the gonadotrophin patterns were studied in blood sampled from these animals every 10 min for up to 72 h during the subsequent follicular phase. Following luteolysis (and the end of bFF treatment), LH pulse frequency increased rapidly in both groups and reached 1 pulse/h within 6 h. Thereafter, pulse frequency increased marginally and reached 1 pulse/50 min by the onset of the LH surge. This pattern was not affected by previous treatment with bFF. In the control ewes, the amplitude of the LH pulses did not change significantly following luteolysis or at any time during the follicular phase, while the levels of FSH declined slowly until the onset of the surge. In the treated ewes, on the other hand, there was an immediate increase in both LH pulse amplitude and the concentration of FSH immediately after the end of bFF treatment at luteolysis, and they remained above control levels for 24 and 16 h respectively. Plasma prolactin levels did not appear to change around the time of luteolysis but showed a marked and significant diurnal rhythm (nadir around noon and peak around midnight) in both groups. The concentrations of prolactin were significantly (P<0·001) lower and the preovulatory peak was delayed and reduced in the bFF-treated ewes relative to controls. The onset of oestrus was also significantly (P<0·01) delayed by bFF treatment, but the ovulation rates did not differ between the groups. Furthermore, comparisons within or between groups revealed no significant relationships between any of the variables of plasma LH secretion during the follicular phase and the subsequent ovulation rate. These observations provide a complete description of gonadotrophin patterns during the follicular phase of the ewe and confirm the suggestion that an increase in LH pulse frequency is the major driving force behind the follicular growth that ultimately leads to ovulation. On the other hand, it appears most unlikely that the pattern of LH secretion during the follicular phase has any influence on ovulation rate. The levels of FSH declined in the period leading up to the preovulatory surge, presumably as a consequence of rising peripheral levels of oestrogen (and/or inhibin). We also expected LH pulse amplitude to decline during the follicular phase because it has been proposed that pulse amplitude is also controlled by oestrogen. The absence of any significant fall in amplitude suggests that hypotheses about the control of LH secretion drawn from studies with ovariectomized ewes require further verification in the intact ewe. The effect of bFF on prolactin levels probably reflects the low rates of secretion of oestradiol by the small ovarian follicles in these ewes. J. Endocr. (1988) 116, 123–135

178 IS PROGESTERONE THE DETERMINING REGULATORY FACTOR BEHIND OVULATION RATE IN EWES?

2015 ◽  
Vol 27 (1) ◽  
pp. 180
Author(s):  
J. Sohal ◽  
V. Paravinja ◽  
T. Baby ◽  
M. Murawski ◽  
T. Schwarz ◽  
...  
Keyword(s):  
Luteal Phase ◽  
Oestrous Cycle ◽  
Ovulation Rate ◽  
Antral Follicles ◽  
Follicular Waves ◽  
Lh Pulsatility ◽  
Lh Release ◽  
The Mean ◽  
Number Percentage ◽  
Ovulatory Follicles

Ovarian antral follicles in the ewe grow in an orderly succession, producing 3–4 waves per oestrous cycle. In prolific sheep, some large antral follicles from the second-last wave of the oestrous cycle are added to the ovulatory follicles emerging just before oestrus to give a higher ovulation rate; it is feasible that regression of these follicles is prevented by an increase in serum concentrations of FSH and/or LH pulsatility at pro-oestrus. Prolific sheep tend to have a shorter luteal phase than non-prolific breeds and there is a great deal of evidence that luteal progesterone (P4), in addition to regulating LH release, may govern the secretion of FSH heralding the emergence of follicular waves. The specific purpose of the present experiments was to determine whether or not extending the duration of the luteal phase would alter the ovulation rate in prolific sheep. In both studies, exogenous P4 (7.5 mg ewe–1 IM) was administered on Days 11 and 12 (Day 0 = ovulation) in moderately prolific Rideau Arcott x Polled Dorset (Exp. 1, n = 8) and highly prolific Olkuska ewes (Exp. 2, n = 7), while the equinumerous groups of animals served as controls (CTR). Transrectal ovarian ultrasonography was performed daily and jugular blood samples were drawn twice a day from Day 9 until ovulation. All single-time point observations were compared between groups by Student t-test. Progesterone injections resulted in uniform increments in serum P4 levels in all animals allocated to the treatment (TRT) groups. However, the mean duration of the interovulatory interval did not differ (P > 0.05) between TRT and CTR groups of ewes in both experiments. The mean (± s.e.m.) ovulation rate was 1.6 ± 0.2 v. 3.2 ± 0.4 (Exp. 1; P < 0.001) and 3.2 ± 0.8 v. 4.0 ± 1.0 (Exp. 2; P < 0.05) in TRT v. CTR ewes, respectively. There were no differences in terms of the timing of penultimate and final wave emergence between the two subsets of animals studied in either experiment. The number/percentage of ovulating follicles from the penultimate wave of the interovulatory interval studied was 0.25 ± 0.16 v. 1.75 ± 0.45 (P < 0.01)/25.0 ± 16.4% v. 75.0 ± 16.4% (P < 0.05) in Exp. 1 and 0.50 ± 0.30 v. 1.60 ± 0.40 (P < 0.05)/13.8 ± 9.0% v. 53.4 ± 16.7% (P < 0.05) in Exp. 2, in TRT v. CTR animals, respectively. In summary, administration of P4 at the end of diestrus reduced the incidence of ovulations from the penultimate wave of the oestrous cycle in moderately and highly prolific strains of sheep. Therefore, progesterone appears to be a key endocrine signal governing the ovulation rate in cyclic sheep, presumably by acting directly at the level of the ovary. The present results may pave a way to devising a simple and inexpensive method of controlling lamb productivity in commercial flocks of sheep and fertility in other polyovulatory species.

Patterns of gonadotropin secretion in cyclic Finn ewes selected for and against high ovulation rate

1995 ◽  
Vol 61 (2) ◽  
pp. 251-257 ◽  
Author(s):  
W. Haresign ◽  
A. C. Cooper ◽  
M. Khalid ◽  
J. P. Hanrahan
Keyword(s):  
Luteal Phase ◽  
Pulse Frequency ◽  
Follicular Phase ◽  
Oestrous Cycle ◽  
Ovulation Rate ◽  
Gonadotropin Secretion ◽  
High Line ◽  
Lh Secretion

AbstractA comparison of the patterns of LH and FSH secretion was undertaken in lines of Finn sheep selected for and against high ovulation rate. Mean ovulation rate was significantly higher in the high line ewes (mean 4·1) compared with both the control (mean 2·5) and low line (mean 2·7) ewes (P <0·01). The pre-ovulatory LH peak occurred significantly earlier in the high line ewes (mean 52·1 h) compared with both the control (mean 65·0 h) and low line (mean 59·0 h) ewes (P < 0·05). While mean LH pulse frequency and overall mean LH concentrations were both significantly higher during the follicular compared with the luteal phase of the cycle (P < 0·05), there were no consistent relationships between patterns of pulsatile LH secretion and ovulation rate among the three selection lines. Plasma FSH concentrations remained significantly higher over the entire follicular phase of the oestrous cycle in the high line ewes compared with both the control and low line ewes (P < 0·05). It is suggested that the ovulation rate achieved by high line ewes may be causally related to their higher follicular phase FSH concentrations.

Ovulation rate and the concentrations of gonadotrophins and metabolic hormones in ewes infused with glucose during the late luteal phase of the oestrous cycle

1995 ◽  
Vol 146 (3) ◽  
pp. 403-410 ◽  
Author(s):  
J A Downing ◽  
J Joss ◽  
R J Scaramuzzi
Keyword(s):  
Luteal Phase ◽  
Follicular Phase ◽  
Oestrous Cycle ◽  
Ovulation Rate ◽  
Metabolic Hormones ◽  
Late Luteal Phase ◽  
Early Follicular Phase ◽  
Lh Secretion ◽  
Effect Of Glucose ◽  
Stimulation Of

Abstract The positive relationship between nutrition and ovulation rate was investigated in sheep infused intravenously with glucose. Ovulation rate increased (2·0±0·0 vs 2·4 ± 0·3) when ewes were given an infusion of glucose (60–65 mm/h) for five days in the late luteal phase of the oestrous cycle. The effect of glucose was obtained without any significant change in LH secretion. The concentration of FSH in glucose-infused ewes was lower during the infusion (luteal phase) but higher during the early follicular phase. These data suggest that the change in ovulation rate occurred without increased gonadotrophin support to the follicle during the late luteal phase, which is the period of the sheep oestrous cycle during which improved nutrition increases ovulation rate. There were no changes in GH or prolactin, but changes in circulating glucose and insulin levels were detected. We conclude that insulin, because of its role in cell growth and metabolism, is involved in mediating ovulation responses to nutritional stimuli, either directly or more likely by the stimulation of insulin-mediated glucose uptake. Journal of Endocrinology (1995) 146, 403–410

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