Luteal Phase Length Research Articles

Intraluteal infusion of a prostaglandin synthesis inhibitor, sodium meclofenamate, causes premature luteolysis in rhesus monkeys.

The physiological significance of locally produced prostaglandins (PGs) in the regulation of the functional lifespan of the primate corpus luteum is unknown. In the current study, the PG synthesis inhibitor sodium meclofenamate was administered to adult female rhesus monkeys beginning in the midluteal phase of the menstrual cycle. Meclofenamate was infused continuously for 7 days into the corpus luteum (100 micrograms/h, n = 6) or the jugular vein (100 micrograms/h, n = 3; 1000 micrograms/h, n = 3) via osmotic minipump. As controls, PBS was infused into the corpus luteum (n = 7) or jugular vein (n = 5). In some of the monkeys receiving intraluteal infusions, chronic aortic and utero-ovarian venous catheters were implanted, and blood samples were collected on alternate days for the measurement of PGE and PGF2 alpha by RIA. Saphenous venous blood was collected daily, and progesterone and cortisol levels were determined by RIA. LH levels were determined by the mouse Leydig cell bioassay. Progesterone levels over 5 days preceding treatment were not different among groups. A decline in progesterone levels on day 1 after surgery was observed in all treatment groups and was accompanied by a 1-day elevation in cortisol levels. Thereafter, five of seven monkeys who received intraluteal infusions of PBS displayed normal progesterone patterns during treatment and normal luteal phase lengths of 15.4 +/- 1.2 days (mean +/- SEM). In six monkeys that received intraluteal infusions of meclofenamate, progesterone levels typically fell to less than 1 ng/ml within 72 h after initiation of infusion; progesterone levels during 7 days of intraluteal infusion were significantly lower (P less than 0.01) in meclofenamate- vs. PBS-treated monkeys. Meclofenamate infusion into the corpus luteum significantly shortened (P less than 0.01) the luteal phase to 10.5 +/- 1.0 days. In contrast, progesterone levels during 7 days of meclofenamate infusion into the jugular vein did not differ from those in PBS-treated monkeys, and the length of the luteal phase was unaltered. LH levels, measured daily, did not differ among groups either before or during treatment. Although an venous/arterial gradient in PGE was detected at the time of surgery, we were unable to detect a significant gradient across the ovary in PGE or PGF2 alpha at any time after surgery in monkeys treated with either PBS or meclofenamate. The present data suggest an obligatory luteotropic role for locally produced metabolites of arachidonic acid, but a physiological role for either PGE or PGF2 alpha in regulating the primate corpus luteum remains equivocal.

Luteal dysfunction in ovulation induction: the role of repetitive human chorionic gonadotropin supplementation during the luteal phase

Several studies have indicated that ovulation induction with human menopausal gonadotropin (hMG)/human chorionic gonadotropin (hCG) or clomiphene citrate (CC) is associated with luteal phase defect. To assess the efficiency of luteal support by hCG to an infertile population undergoing ovulation induction, with CC/hCG or hMG/hCG, we have randomly administered 2500 IU hCG intramuscularly on days 3, 6, and 9 after ovulation induction by 10,000 IU of hCG to 74 patients on 265 treatment cycles. As controls served 357 ovulation induction cycles in the same 74 patients. The treatment cycles were randomly alternated with control cycles so that each patient served as her own control. However, the mean +/- standard deviation (SD) midluteal P was 38.1 +/- 10.8 ng/ml in the study group versus 15.7 +/- 10.5 ng/ml in the control group (P less than 0.001). Luteal phase length was 15.4 +/- 1.5 days in the treatment group versus 12.1 +/- 1.7 in the control group (P less than 0.01). In the treatment group, 64.8% of the patients achieved pregnancy (27% pregnancies/treatment cycle) versus 47.3% in the control group (11.5% pregnancies/control cycle) (P less than 0.01). The pregnancy wastage rates (including abortions and "chemical" pregnancies) were 30.6% in the treatment group versus 56% in the control group (P less than 0.01). We conclude that repetitive hCG administration may be an efficient luteal support in infertile patients undergoing ovulation induction.

Predictive value of the FSH: LH ratio on follicular and luteal phase characteristics of the human menstrual cycle

A prospective study was designed to assess the predictive value of gonadotropin measurements obtained during the early follicular phase upon the hormonal characteristics of the subsequent cycle. The data obtained in 12 normal cycles were used to compute the mean and confidence interval (mean ± 2 SEM) of the FSH: LH ratio, FSH and LH plasma levels. The limits of the confidence intervals for these different parameters were used to classify the patients. Data of 204 patients were analysed. Low FSH: LH ratios (< 1.34) are associated with an increase in follicular phase length (+2.4 days), a lower ovulatory rate, but neither luteal phase length nor progesterone levels differ between these two groups. When patients are classified according to FSH levels, our results show that low FSH levels (< 2.94 mIU/ml) are associated with longer follicular (+2.6 days) and shorter (−1.1 days) luteal phase lengths, but ovulatory rate and progesterone levels in the luteal phase of the ovulatory cycles are similar to those obtained in patients of the normal or high FSH group. High LH levels (> 3.15 mIU/ml) are associated with a decreased ovulation rate but follicular and luteal phase characteristics are similar to those obtained in patients in the normal or low LH group. In conclusion, low FSH: LH ratios and low FSH plasma levels measured in the early follicular phase of the cycle are associated with longer follicular phase lengths; but basal gonadotropin measurements have limited predictive value on luteal phase characteristics.

A randomized comparative study of purified follicle stimulating hormone and human menopausal gonadotropin after pituitary desensitization with Buserelin for superovulation and in vitro fertilization

Twenty patients entered a randomized, crossover study of purified follicle-stimulating hormone (pure-FSH) or human menopausal gonadotropin (hMG) superovulation, 2 ampules per day after pituitary desensitization with the luteinizing hormone-releasing hormone (LH-RH) analogue Buserelin (D-Ser tBu6 LH-RH 1-9 ethylamide) nasal spray. There were no cycles cancelled. Six patients conceived (five on pure-FSH, one on hMG). There were 24.2 +/- 2.5 (mean +/- standard error of the mean [SEM]) ampules of pure-FSH and 24.3 +/- 3.6 ampules of hMG stimulation required. There were similar numbers of preoperation follicles: 6.9 +/- 1.0 on hMG and 6.6 +/- 1.1 on pure-FSH, of oocytes collected; 8.5 +/- 1.4 on hMG and 5.8 +/- 1.4 on pure-FSH, and of pre-embryos achieved; 5.1 +/- 0.9 on hMG and 3.4 +/- 1.0 on pure-FSH; on either treatment. The fertilization rate on hMG was 60% and on pure-FSH was 55%. Pre-embryo transfer rates were 3.2 +/- 0.3 in the hMG group and 2.7 +/- 0.4 in the pure-FSH group. There were no differences in serum FSH, LH, estradiol, or progesterone levels between the hMG and pure-FSH groups. Mean +/- SEM luteal phase length was 10.6 +/- 0.4 days in the nonpregnant cycles.

A comparison of dosages of norethisterone for synchronization of cycles in a fixed regimen of follicular augmentation and in vitro fertilization

Twenty-four patients undergoing elective laparoscopic sterilization were randomized in a fixed schedule of follicular augmentation, oocyte recovery, and in vitro fertilization (IVF) using either 2.5 or 10 mg of norethisterone (NE) in the luteal phase of the previous cycle. The objectives of the study were to determine the effect of a synthetic progestin, given for 5 to 14 days beginning on day 21 of the cycle before the IVF cycle, on folliculogenesis, estrogen secretion, the luteinizing hormone (LH) surge, luteal function, and IVF success. It was found that this treatment was easy to administer and well tolerated by patients. At the 10-mg dose, patients uniformly had vaginal bleeding 2 to 4 days after NE, whereas 40% of patients using the 2.5-mg dose bled before NE was discontinued. Significantly lower estrone glucuronide excretion in the early follicular phase and lower luteal phase pregnanediol excretion in patients receiving 10 mg NE suggested a delay or reduction of developing follicles after luteal phase suppression. No spontaneous LH surges were found in the 10-mg group, compared with surges in 5 of the 13 cycles of the 2.5-mg group. There were no differences between regimens in cycle or luteal phase length. It is postulated that NE, by suppressing folliculogenesis in the luteal phase, may provide for a smaller, but more homogenous cohort of follicles available for exogenous stimulation and recovery.

Ovarian function in the elephant: luteinizing hormone and progesterone cycles in African and Asian elephants.

Serum samples were collected weekly for 3 yr from two female African elephants, for 18 mo from two other female African elephants, and for 2 yr from two female Asian elephants. Animals were not sedated at the time of blood collection. Ovarian cycles, characterized by changes in progesterone and immunoreactive luteinizing hormone (ILH) concentrations, averaged 15.9 +/- 0.6 wk (N = 25) for African females and 14.7 +/- 0.5 wk for Asian females (N = 10). The length of the active luteal phase averaged 10.0 +/- 0.3 wk for African elephants (range 8-14 wk) and 10.6 +/- 0.6 wk for Asian females (range 9-13 wk). Interluteal phases were 5.9 +/- 0.6 wk for African females and 4.2 +/- 0.5 wk for Asian females. One African female (Maliaca) had two extended interluteal phases, both occurring between the months of February and May. Excluding these two periods, there were no differences in the length of the ovarian cycle or the length of the luteal phase between species of elephant. Serum progesterone in both species ranged from less than 50 pg/ml to 933 pg/ml. Average progesterone concentrations during the luteal phase were significantly lower in African elephants compared with Asian elephants (328 +/- 13, N = 30 cycles vs. 456 +/- 23, N = 14 cycles; p less than 0.001). ILH ranged from nondetectable to 11.6 ng/ml. These data suggest that the length of the ovarian cycle in the African elephant is about 16 wk and confirm that the length of the ovarian cycle in the Asian elephant is about 15 wk.

A randomized trial of human chorionic gonadotropin support following in vitro fertilization and embryo transfer

This article reports on the effects of human chorionic gonadotropin (hCG) on progesterone (P) and estradiol (E2), luteal phase length, and conception in 116 cycles treated by in vitro fertilization and embryo transfer (IVF-ET). In 60 cycles, the luteal phase was supported by hCG, 1500 IU three times at 2-day intervals from the day of ET. The remaining 56 cycles served as controls. hCG significantly increased the P level (93 +/- 53 versus 62 +/- 46 ng/ml), the P/E2 ratio, and the luteal phase length (17.4 +/- 1.3 versus 12.2 +/- 1.7 days). However, the total pregnancy rate did not significantly differ between the two groups, though the pregnancy rate after transfer of two or three embryos was slightly higher in the hCG group (26.9 versus 22% in the control group), as was the rate of implanted embryo per transferred embryo after transfer of two or three embryos (25 versus 15.3%). It was concluded that, while hCG increased the magnitude and duration of the luteal P secretion, it did not clearly improve the pregnancy rate.

Hypoprolactinemia and ovarian function

Thirty-two patients with ovarian hyperstimulation were randomized to receive bromocriptine or placebo from cycle day 5 onward. Bromocriptine decreased serum and follicular fluid prolactin (PRL), accelerated ovarian follicle growth, increased serum and follicular fluid estradiol, lowered luteal phase progesterone, and shortened the luteal phase length of the cycle. The maximal luteal phase estradiol and progesterone concentrations correlated with each other in the placebo group, but not in the bromocriptine group. These findings indicate that hypoprolactinemia interferes with ovarian function. The unchanged concentrations of gonadotropic hormones and pattern of luteinizing hormone pulsation during bromocriptine suggest direct ovarian effects of hypoprolactinemia. Because PRL suppression enhanced follicular responses and inhibited corpus luteum formation and function, the follicular and corpus luteum actions of PRL may be different.

The effects of clomiphene citrate on the histology of human endometrium in regularly cycling women undergoing in vitro fertilization

Thirty-six women with histories of regular cycles undergoing elective laparoscopic sterilization volunteered to participate in a research program of endometrial biopsy, oocyte donation, and in vitro fertilization (IVF). One half of the volunteers received 5 days of 150 mg of clomiphene citrate (CC) ending 5 days before human chorionic gonadotropin injection and 6.5 days before laparoscopy and biopsy. The control patients were treated identically, except they received no CC. CC cycles were more uniform in duration and follicular response better, enabling a prescheduled IVF regimen. Control cycles were complicated by poor follicular response or untimely endogenous surges of luteinizing hormone (LH). The mean urinary estrone glucuronide excretion per follicle was the same in each group, and there was no evidence of a luteal defect by either luteal phase length or urinary pregnanediol excretion. Although there were minor differences in mitotic rate and basal vacuolation of glandular epithelium in biopsies, no specific deleterious effect of CC could be seen.

Induction of atresia of the dominant follicle in rhesus monkeys (Macaca mulatta) by the local application of estradiol-17β.

Estradiol-17β (E2), administered systemically to rhesus monkeys during the follicular phase of the menstrual cycle, induces atretic changes in the microenvironment of the dominant follicle (DF), which results in its demise. It has been proposed that this effect of E2 represents a direct action at the ovarian level. The present study was designed to test this hypothesis, using local treatment with E2. After identification of the DF during laparoscopy on day 6 of the cycle, female monkeys were laparotomized and their ovaries exposed. Either corn oil (20 μl, controls) or E2 (100 μg ) in oil vehicle (experimentals) was injected into the ovary near the DF. In control animals, preovulatory release of gonadotropins and ovulation were normal in five of six animals, with cycle and luteal phase lengths of 27.8 ± 2.2 days and 14.6 ± 2.5 days, respectively (x̄ ± S.D.). Conversely, in only one of six animals in the experimental group did ovulation occur at the expected time (P < 0.05). In the other five treated animals, E2 induced atresia of the DF and significantly extended cycles (35.4 ± 5.4 days) without affecting luteal phase lengths (12.0 ± 1.4 days). Concentrations of estrogen in peripheral sera of some animals were increased transiently at 6 h after injection of E2 but returned to normal by 12 h; this duration of estrogen exposure is far less than the 24 h required to induce atresia of the DF in previous studies. At 6 h after injection of E2, there was a statistical difference between controls and experimentals in concentrations of circulating estrogen; however, these changes were apparently not enough to alter pituitary secretion of follicle-stimulating hormone or luteinizing hormone. These data support the hypothesis that E2 can induce atresia of the DF in rhesus monkeys by acting locally at the ovary.

Menstrual cycles in rhesus monkeys (Macaca mulatta) are unaffected by a single dose of the anesthetics ketamine and xylazine administered during the midfollicular phase at laparoscopy.

To identify an anesthetic regimen that produces more complete relaxation and analgesia than ketamine hydrochloride (Ketaset®) alone, a combination of ketamine (15 mg/kg body weight) and the hypnotic xylazine (Rompun®, 0.33 mg/kg) was evaluated. Since the desired experimental application required that the anesthetic not interfere with normal hormonal events during the menstrual cycle, this combination administered on day 6 of the cycle was tested to determine whether hormonal surges, incidence of ovulation, or cycle length would be altered relative to the use of ketamine alone. In five of six animals, ketamine plus xylazine had no effect on the occurrence of timely surges of estrogen, luteinizing hormone (LH), or follicle-stimulating hormone (FSH), or on ovulation as determined by the presence of a corpus luteum at laparoscopy and normal serum concentrations of progesterone. There were no significant differences between the cycle during treatment and previous cycles in the same animal for length of the menstrual cycle (26.0 ± 2.3 [5] days; X̄ ± S.D. [n] or luteal phase (13.4 ± 2.4 [5] days). Likewise, these values did not differ from those of ten control monkeys treated with ketumine only on day 5 or 6 of the cycle (incidence of ovulation, 10/10; cycle length, 27.9 ± 1.8 [10]; luteal phase length, 15.1 ± 1.4 [10], P > 0.05). Patterns of circulating progesterone were not altered by the addition of xylazine anesthesia. These findings indicate that xylazine, given in the midfollicular phase, did not alter ovulatory events or menstrual cycle characteristics in rhesus monkeys. Ketamine plus xylazine apparently provides anesthesia appropriate for laparoscopy.

Pharmacologic production of luteinized unruptured follicles by prostaglandin synthetase inhibitors

Serial ultrasonic scans of follicular development were performed throughout 46 spontaneous cycles in 20 healthy female volunteers. Human chorionic gonadotropin was then given to induce follicle rupture on a particular day. Luteinized unruptured follicles (LUFs) were seen in 10.7% of untreated cycles. When prostaglandin synthetase inhibitor drugs were administered over the ovulatory period the incidence of LUF was greatly increased (to 50% with azapropazone and 100% with indomethacin). Serum estradiol concentrations and length of luteal phase were unaltered in LUF cycles. Progesterone concentrations were lower in the first half of the luteal phase if follicles remained unruptured.

Is the decrease in the hypophysiotropic signal frequency normally observed during the luteal phase important for menstrual cyclicity in the primate?

The two phases of the ovulatory menstrual cycle of the primate are characterized by divergent activities of the GnRH pulse generator. During the luteal phase, LH pulse frequency is significantly reduced below that observed during the follicular phase. In this report we investigate whether the decrease in pulse frequency during the luteal phase is of physiological relevance to normal menstrual cyclicity. We have tested the effect of a pulsatile GnRH infusion given iv at hourly intervals for a period of 8-10 days during the luteal phase on the subsequent three to five cycles in eight female rhesus monkeys. Three of the eight animals received two treatment courses. Amounts of GnRH infused were 1.5 micrograms/pulse (n = 2 trials); 3.0 micrograms/pulse (n = 7); and 4.0 micrograms/pulse (n = 2). LH response to GnRH pulses of 1.5 and 3.0 micrograms resembled spontaneous LH pulses observed during the luteal phase. During the GnRH infusion period, the monkeys were fitted with a primate vest and tethered. Eleven control experiments were performed in these monkeys under similar conditions. GnRH therapy during the luteal phase affected subsequent cycles significantly, while no differences were observed in the control experiments. Overall mean follicular phase length in the control cycle was 13.4 days; it was significantly increased (P less than 0.005) in all post-GnRH treatment cycles to reach 34.4 (+/- 10.9), 43.9 (+/- 12.7), 40.4 (+/- 13.0), and 23.1 (+/- 4.8) days (+/- SE) in the first to fourth post-GnRH cycles, respectively. Progesterone secretion was significantly lower (P less than 0.05) in the first two post-GnRH cycles than in the control cycles: progesterone, 46.4 (+/- 2.1) in all control cycles, decreased to 27.7 (+/- 3.7), 24.8 (+/- 4.3), 34.0 (+/- 5.4), and 32.0 (+/- 6.5) surface units (+/- SE) from the first to fourth post-GnRH cycles, respectively, while luteal phase length remained relatively unchanged. The data indicate that significant disturbances in the menstrual cycle of the rhesus monkey follow imposed changes in the normal frequency pattern of the GnRH hypophysiotropic signal during the luteal phase and suggest that the naturally occurring slowing of GnRH-LH pulse frequency during the luteal phase is a relevant phenomenon in the sequence of events which control menstrual cyclicity.

Endometrial cytosolic and nuclear progesterone receptors in the luteal phase defect.

Basal body temperature profiles, serial serum progesterone levels, and serial endometrial biopsies were studied in 15 infertile women during 21 ovulatory cycles. Ten cycles (in 9 women) demonstrated luteal phase defects (LPD), diagnosed by a histological lag in endometrial maturation, normal luteal phase length, and normal luteal phase serum progesterone levels. Both normal and LPD cycles had a maximum amount of endometrial cytosolic progesterone receptor (PgR) on days 13-15, with a significant decline thereafter. LPD cycles had significantly lower endometrial nuclear PgR concentrations than did normal cycles during the proliferative phase, but luteal phase endometrial nuclear PgR levels were similar in both groups. In 2 LPD women treated with dydrogesterone, normal endometrial maturation and a decline in endometrial cytosolic PgR concentrations in the late luteal phase were found. Therefore, with the exception of endometrial nuclear PgR concentrations during the proliferative phase, we found no evidence for a major abnormality in endometrial PgR levels in LPD cycles with a lag in endometrial histology.

Serum gonadotrophin and sex steroid hormone levels during mid-follicular and mid-luteal phases in hyperprolactinaemic women with regular menstrual cycles.

Hyperprolactinaemia was found in 15 of 135 infertile patients with regular menstrual cycles, biphasic basal body temperature record and no galactorrhoea. In those 15 women, mean serum prolactin levels during the mid-follicular and mid-luteal phases of the menstrual cycle were 29.8 (SEM 1.8) ng/ml and 29.5 (SEM 1.3) ng/ml, respectively. Although serum FSH and LH levels were similar in normal and hyperprolactinaemic women, serum oestradiol level during the mid-follicular phase was subnormal in hyperprolactinaemic women (P less than 0.05). In contrast, serum oestradiol and progesterone levels during the mid-luteal phase and luteal phase length were similar in normoprolactinaemic and hyperprolactinaemic groups. The results suggest that hyperprolactinaemia is associated with defects of follicle development as measured by oestradiol production during the mid-follicular phase, but not with corpus luteum function as measured by progesterone production during the mid-luteal phase, and luteal phase length.

The effects of inducing a follicular phase gonadotropin secretory pattern in normal women during the luteal phase

It has been hypothesized that the slowing of the luteinizing hormone (LH) pulse frequency in the luteal phase may be necessary for the demise of the corpus luteum, the intercycle rise in baseline follicle-stimulating hormone (FSH), or ovarian follicular development in the subsequent cycle. For assessment of the physiologic role of the luteal phase LH pulse pattern, this pattern was converted to a follicular pattern in six normal women who used exogenous gonadotropin-releasing hormone administered with a portable pump (dose 50 to 100 ng/kg subcutaneously every 90 minutes beginning in the early luteal [n = 3] and midluteal [n = 3] cycle phases). There was no significant difference between the treated and the subsequent cycle for luteal progesterone production [186.3 versus 159.0 (ng/ml) day], preovulatory follicular size (23.1 versus 22.5 mm), estradiol levels, luteal phase length (15.6 versus 14.3 days), and daily gonadotropin concentrations including the intercycle FSH rise (160.5 versus 139.1 ng/ml). A follicular phase gonadotropin pulse pattern (increased frequency, decreased amplitude) in the luteal phase had no discernible effects on the corpus luteum or on follicular development in the subsequent cycle.

Progesterone and luteinizing hormone profiles in heifers used as oocyte donors

Progesterone (P 4) and luteinizing hormone (LH) profiles were analyzed throughout the estrous cycle in 11 superovulated heifers that had follicular oocytes aspirated at different times after standing heat. It was found that high P 4 during estrus was incompatible with normal LH release, oocyte maturation and subsequent in vitro fertilizing capability. However, an LH peak was not a prerequisite for initiation of meiosis, since both metaphase I (MI) and metaphase II (MII) stages were observed in animals without an LH surge. Following follicular aspiration, the progesterone levels and the length of luteal phase were similar to those of superovulated animals that had no follicular intervention. We concluded that aspiration per se does not interfere with normal corpora lutea (CL) development in heifers when aspiration occurs after the LH surge.

Serum progesterone levels in women treated with human menopausal gonadotropin and human chorionic gonadotropin for in vitro fertilization

For evaluation of the adequacy of luteal function after in vitro fertilization-embryo transfer (IVF-ET), serum progesterone (P) levels were measured on days 3, 7, and 10 after laparoscopic follicle aspiration. Fifty-six infertile patients were treated during 86 cycles with human menopausal gonadotropin-human chorionic gonadotropin (hMG-hCG) for stimulation of follicular development. Serum estradiol (E2) levels were measured daily during hMG-hCG treatment. P levels were determined in 67 cycles. The mean (+/- standard deviation [SD]) of the sums of 3 P levels was 55.63 +/- 24.13 ng/ml. There were 11 pregnancies. The mean of the sums of 3 P levels of pregnant patients was 64.45 +/- 26.23 ng/ml and of 56 nonpregnant cycles was 53.90 +/- 23.35 ng/ml. The duration of luteal phase varied from 9 days to 15 days. The mean of the sums of 3 P values of patients with different luteal phase lengths ranged from 28.8 ng/ml to 60.51 +/- 25.68 ng/ml. The mean of the sums of 3 P levels of women with normal luteal phase and that of women with luteal phase defect by endometrial biopsy study were used as controls for comparison. There was poor correlation (r = 0.3441) between E2 peak levels and P levels; the sum of 3 P levels did not indicate luteal phase inadequacy in IVF-ET patients; and the majority of the nonpregnant cycles (32/56) showed a luteal phase of 11 days or less, in spite of adequate P levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Sequential Hormonal Changes in the Postpartum Dairy Cow

Peripheral plasma levels of 15-keto-13,14-dihydro-PGF2α, progesterone, Cortisol, LH and prolactin were studied in 6 primiparous postpartum dairy cows. The cows were followed by hormone measurements and clinical examinations from parturition until pregnancy was established. Blood was collected 3 times per day. The cervix, uterus and ovaries were examined by rectal palpation at 6–10 days intervals. The cows were observed for signs of oestrus twice daily and were additionally teased with a bull to provoke standing heat. Four cows had a normal parturition and dropped their fetal membranes shortly afterwards. (NR group). The remaining 2 retained their fetal membranes for more than 24 h following parturition (RFM group). One out of 6 cows showed standing oestrus at the first ovulation, 4 animals were in oestrus at the second ovulation and all cows showed signs of oestrus at the third ovulation. Although the length of the first luteal phase varied from 9 to 22 days a corpus luteum was in all cases palpated. The secretion of progesterone during the first luteal phase was terminated by a PGF2α release. A significant difference in 15-keto-13,14-dihydro-PGF2α levels between the 2 groups was found on days 0–4 (2.39 vs 6.87 nmol/1 at Ρ < 0.06). Postpartum prostaglandin F2α release as reflected by the level of 15-keto-13,14-dihydro-PGF2α lasted shorter in the NR group than in the RFM group (15–17 vs 21 days). Significant positive correlations between 15-keto-13,14-dihydro-PGF2α and Cortisol as well as between prolactin and Cortisol during the first 24 days postpartum were noted only in cows having normal parturition. The most pronounced daily prolactin variations occurred during the second luteal phase (NR group), when a significant difference between the times 8.00, 12.00 and 15.00 was recorded (14.7, 31.5 and 19.7 μg/l, respectively). Moreover, a partial negative correlation between log value of prolactin and arithmetical value of LH was found in these cows only during the first luteal phase after parturition.

A survey of reproductive performance in dairy herds. Characteristics of the patterns of progesterone concentrations in milk

ABSTRACTProgesterone concentrations were measured by radioimmunoassay in fat-free milk samples obtained three times weekly from calving until day 60 of pregnancy from over 700 cows in commercial dairy herds. Profiles of progesterone concentration during the ovulatory cycle and early pregnancy were also examined. In 94% of the animals cycling had commenced by 60 days post partum and a further 3% had shown some ovarian activity. In 34% of cows, the resumption of regular ovulatory activity was preceded by short periods of progesterone secretion which did not meet the criteria for a 'normal cycle’. Peaks of progesterone cross-reactivity (&gt;0·75 ng/1) were detected at the time of ovulation in proportionately 0·06 of all cycles. There was no relationship between the detection of oestrus and the length of the following progesterone cycle or the concentrations during that cycle. However, there was a tendency for the first progesterone cycle post partum to be more variable in length than later cycles (0·56 within the range 18 to 24 days compared with 0·70 of later cycles; P &lt; 0·001). Extension of the length of the luteal phase occurred in 58 second and later cycles (proportionately 0·141) following inseminations which did not result in calving. However, since the comparable figure for 1053 cycles where no insemination was given was 0·048, the overall figure for embryo mortality later than 24 days after insemination was estimated as 9·3%. Concentrations of progesterone in pregnant animals, compared to non-pregnant animals, and the distributions of luteal lengths between 8 and 21 days long following inseminations not resulting in calving could both be explained by early maternal recognition of pregnancy.