Fetal growth and reproductive performance in ewes administered GnRH agonist on day 12 post-mating

Reproductive performance and fetal growth was determined in GnRH (4 microg synthetic GnRH agonist, Receptal) administered (i.m.) to ewes on day 12 post-mating (n = 103) compared to control ewes (n = 97) during the breeding season. Plasma progesterone and LH concentrations were analyzed. A total of 13 ewes was slaughtered on day 45 of pregnancy (six from control, seven from GnRH treated groups). GnRH administration on day 12 post-mating increased plasma progesterone concentration (4.39+/-0.25 ng/ml) compared to control group (3.43+/-0.15 ng/ml) on days 13-15 post-mating (P < 0.01). GnRH administration also increased plasma LH concentration between 1 and 4 h after GnRH administration (P < 0.01). Pregnancy rate was higher in GnRH treated group (84%) than control (66%) group (P < 0.05). The ewes in GnRH administered group had more twins (P < 0.05) than those in control group. The ovarian weights (P < 0.05) and the number of corpora lutea (CL) (P < 0.01) were greater in ewes slaughtered on day 45 of pregnancy in GnRH treated group than those in control group. GnRH administration on day 12 post-mating did not have any effect on products of conception at day 45 of pregnancy except on crown-rump length (CRL) of fetuses and cotyledon weight. CRL of fetuses and cotyledon weight in GnRH treated group was higher than those in control group (P < 0.05). In conclusion GnRH administration improved reproductive performance of ewes when administered on day 12 post-mating probably through its beneficial effect on embryo survival by enhancing luteal function, but not through stimulating fetal growth.     

A method to reduce the invasiveness of fetal catheterization in the cow

Surgical intervention in general anesthesia (GA) of the cow in late gestation is a stressful condition for both mother and fetus, potentially leading to premature delivery or fetal death. The present study hypothesized that fetal catheterization at days 246–253 (90% of gestation) is done with less physical and metabolic stress for the mother and fetus, when the surgery is performed on a standing cow and local anesthesia (LA) rather than on a recumbent cow in general anesthesia. Fetal and uterine maternal intra-vascular catheters were implanted during general anesthesia (GA, n=24) or local analgesia (LA, n=7). Blood gases and metabolite levels in the fetal calves and their mothers were measured during surgery and for 5 days post-operatively. During surgery, venous blood pH was higher (7.44±0.01 versus 7.39±0.01, P<0.05) and hemoglobin and oxygen contents lower in LA cows compared with GA cows (9.3±0.3 mg/dl versus 11.8±0.2 mg/dl, P<0.001 and 10.1±0.3 ml/dl versus 12.6±0.6 ml/dl, P<0.05). The differences between the two groups of fetuses reflected those of their dams in that LA fetuses showed lower arterial oxygen pressure (18.3±1.4 mmHg versus 24.8±1.4 mmHg, P<0.05) and hemoglobin (7.81±0.30 mg/dl versus 9.22±0.21 mg/dl P<0.01) and furthermore, they also showed higher blood glucose (2.4±0.2 mM versus 1.4±0.1 mM, P<0.01). During the 5 days post-surgery, 10 GA fetuses (42%) and 1 LA fetus (14%) died in utero. Bacterial contamination was implicated in six of the GA deaths and in the one LA death. In the dams with surviving calves, differences in hemoglobin (9.49±0.21 mg/dl versus 11.17±0.23 mg/dl P<0.001) and O₂ct (10.9±0.3 ml/dl versus 12.5±0.5 ml/dl, P<0.05) were still present, and in addition, blood glucose was higher in LA versus GA cows (4.3±0.2 mM versus 3.8±0.1 mM, P<0.05). The choice of surgical method did not affect post-surgery blood chemistry in the surviving fetuses, except that the higher blood glucose in the LA fetuses at surgery tended to be maintained also post-operatively (2.0±0.2 mM versus 1.5±0.1 mM, P=0.07). The observed differences in blood chemistry parameters between the two methods of surgery and possibly in the fetal death may be explained by differences in catheterization method and the associated differences in physical and metabolic stress during and after surgery. Thus, surgery upon a standing cow in local anesthesia should be considered as an alternative to surgery in universal anesthesia for fetal catheterization in the cow in late gestation.     

Maternal serum progesterone concentration during pregnancy and lamb birth weight at parturition in Javanese Thin-Tail ewes with different litter sizes

Pregnant ewes, (N=38), with similar body weight and age (19, 13 and 6 carrying 1, 2 and 3 fetuses, respectively) were used to study the relationship between maternal serum progesterone concentration during pregnancy and lamb birth weight at parturition. Average maternal serum progesterone concentration in the ewes carrying 1, 2, and 3 fetuses was: 5.3±0.3, 6.2±0.7 and 6.6±0.5 ng/ml, during weeks 0 to 7 of gestation; 16.9±1.4, 25.3±1.5, and 26.8±2.5 ng/ml, during weeks 8 to 20; and 13.2±1.0, 18.7±1.0, and 19.8±1.7 ng/ml, during the entire gestation period respectively. Total lamb birth weight in ewes carrying 1, 2, and 3 fetuses was 1.9±0.1, 3.2±0.2, and 4.2±0.4 kg, respectively. In the respective litter sizes, ewes with higher mean serum progesterone concentration during the whole pregnancy gave birth to lambs with higher birth weight (r²=0.76, 0.42 and 0.46, for ewes carrying 1, 2 and 3 fetuses, respectively). The results of the study indicated that prenatal growth could probably be improved by increasing endogenous secretion of maternal progesterone during pregnancy.     

Function of abnormal corpora lutea in vitro after GnRH-induced ovulation in the anoestrous ewe

Normal and abnormal corpora lutea were recovered from anoestrous Romney Marsh ewes on Days 3, 4, 5 and 6 after treatment with small-dose (250 ng) multiple injections of GnRH followed by a bolus injection (125 micrograms) with (+P) and without (-P) progesterone pretreatment and a study made of their characteristics in vitro. Plasma progesterone concentrations initially rose concurrently in all animals but abnormal luteal function occurred in 70% of the -P ewes and was defined on Day 5 when plasma progesterone concentrations declined relative to those in the +P ewes. All corpora lutea recovered on Days 3 and 4 appeared macroscopically similar and there were no significant differences between the +P and -P groups in terms of luteal weight, progesterone content and binding of 125I-labelled hCG on these days. However, corpora lutea from the -P animals only exhibited a decline in progesterone production in vitro on Day 4 (P less than 0.01), and morphological differences became apparent on Days 5 and 6 when the abnormal corpora lutea from the -P animals also decreased in weight (P less than 0.01) and progesterone content (P less than 0.001). Binding of 125I-labelled hCG increased on Day 5 in the normal corpora lutea only. These results show that, although abnormal luteal function induced by GnRH treatment of anoestrous ewes could not be distinguished from normal corpora lutea before Day 5 by measurement of progesterone in peripheral plasma, a significant decline in progesterone production in vitro occurred on Day 4 in the abnormal corpora lutea. This was followed by significant decreases in weight and progesterone content and a failure to increase 125I-labelled hCG binding. Abnormal corpora lutea are therefore capable of some initial growth and progesterone production, before undergoing a rapid and premature regression from Day 4, which has similar characteristics to natural luteolysis.     

Association between numbers of ovarian follicles in the first follicle wave and superovulatory response in ewes

The aim of this study was to examine the variability in the number of ovarian follicles in sheep and to determine if the average number of follicles per day influences the response to superovulation and resulting embryo quality. Ewes (n = 83) were synchronized and the number of follicles (≥2 mm diameter) in the ovaries were counted daily between Days 0 and 4 of the oestrous cycle using transrectal ultrasonography. Fourteen to 21 days later, 47 ewes were randomly chosen from the group and were treated with an intravaginal progestagen pessary for 12 days and superovulated with 1500 IU eCG administered as a single injection 10 days after sponge insertion. Ewes were mated and reproductive tracts were recovered after slaughter on Day 6 of pregnancy. The number of corpora lutea was counted, uterine horns were flushed and the morphology and developmental stage of the recovered oocytes/embryos was assessed. The mean daily number (±S.D.) (≥2 mm diameter) of follicles per ewe was 8.5 ± 2.8 (ranging between 3 and 16). After superovulation animals with few follicles (Low group: <8 follicles/day; n = 21) had fewer (P < 0.005) corpora lutea, total structures (unfertilized oocytes and embryos), good quality and total embryos compared to animals with many follicles (High group: ≥8 follicles/day; n = 23). No difference was found in the proportion of good quality embryos (relative to the total number; Low 0.68 ± 0.11 versus High 0.79 ± 0.08; P = 0.21) between the two groups, or the recovery rate, the number of unfertilized oocytes or the number of poor quality embryos per animal. We conclude that ewes with a higher number of follicles (≥8) during the first follicular wave had a better superovulatory response (in terms of corpora lutea and high quality embryos) 2–3 weeks later; however, there was no relationship between the number of follicles and the proportion of good quality embryos per animal.     

Plasma progesterone concentrations during early pregnancy in spring- and autumn-bred ewes

The objective of this experiment was to measure blood progesterone concentrations during early gestation to determine if the apparent reproductive failure in ewes bred out-of-season is due to a failure to conceive or embryonic loss. Blood samples were collected from spring- (n=61) and autumn-bred ewes (n=29) from Days 8 to 39 post-oestrus. Serum progesterone concentrations were analysed to ascertain whether ewes were ovulating and failing to maintain pregnancy, or conception was failing. Following pregnancy diagnosis 62 days after ram introduction, ewes were categorised as; no display of oestrus, mated but then identified as non-pregnant, or pregnant. A majority of spring-bred ewes that failed to display oestrus had silent oestrus (86%) and 66% of those ewes had abnormally short-lived corpora lutea. Circulating progesterone concentrations during dioestrus in ewes that had ovulated and displayed oestrus were unaffected by season. Similarly, progesterone concentrations during dioestrus did not differ between pregnant and mated non-pregnant ewes. The results indicated that while early luteylosis, low progesterone secretion from corpora lutea and embryo mortality did occur, these were in only a small proportion of ewes. Progesterone concentrations indicated that a majority of mated non-pregnant ewes had elevated progesterone concentrations necessary for the production of at least one viable embryo/foetus. This may be indicative to the failure of maternal recognition of pregnancy, and it is recommended that events surrounding this stage of pregnancy (Days 12-14) be examined more closely in ewes during the non-breeding season.     

Effects of a single injection of hCG or GnRH agonist on day 12 post mating on fetal growth and reproductive performance of sheep

Reproductive performance and fetal growth were determined when hCG (150 i.u. Pregnyl; n=44), GnRH (4 microg synthetic GnRH agonist, buserelin, Receptal; n=43) or saline (control, n=45) was administered (i.m.) to ewes on day 12 post mating during the breeding season. A total of 12 ewes was slaughtered on day 45 of pregnancy (four from each treatment group). Non-return rate and lambing rate were higher for ewes in the hCG (0.89 and 84%) and GnRH treated groups (0.86 and 79%) than for ewes in the control (0.69 and 62%) group (P<0.05). The ewes in the hCG and GnRH groups also had more twins (P<0.05). Birth weights of these twin lambs in the hCG and GnRH groups were heavier than those in the control group (P<0.05), but this difference had disappeared at weaning 60 days later. Lamb mortality was similar among treatment groups resulting in a higher number of lambs weaned in the hCG and GnRH groups. The ovarian weights and the number of corpora lutea (CL) and luteal weights of ewes slaughtered on day 45 of pregnancy were greater (P<0.05) in the hCG and GnRH treated groups than those measured in the control group. Administration of hCG on day 12 post mating increased gravid uterus weight, crown-rump-length (CRL), chorioallantois weight and total cotyledon weight (P<0.05) of conceptuses recovered on day 45 of pregnancy compared to the control group. The weights of caruncules (P<0.05) and placenta (P<0.01) were higher in conceptuses of both the hCG and GnRH groups. The weights of fetuses in the hCG group were higher than those in both the GnRH and control groups (P<0.05). In conclusion, both hCG and GnRH administration improved reproductive performance of ewes when administered on day 12 post mating. However, hCG and GnRH appeared to act differently on embryo survival because only hCG administration increased fetal growth.     

Changes in feeding level during early pregnancy affect fertility in gilts

Modified feeding combining the benefits of restricted feeding after ovulation and abundant feeding during implantation in autumn was tested. Three groups of eight gilts were housed with individual feeding stalls and fed 40 MJ per day of a commercial ration. Following insemination gilts were fed 27 MJ per day (LLL) or 54 MJ per day (HHH) for 34 days or 27 MJ per day for 10 days, 54 MJ per day for 7 days followed by 27 MJ per day until day 34 (LHL). Blood for progesterone analysis was collected daily during the week of ovulation and then twice a week until the end of the study. For LH assay, blood was collected from five gilts from each group at 15 min interval for 10 h on the day 15 of pregnancy. Gilts were weighed three times at intervals of 4 weeks. The effect of dietary treatment was significant (P<0.05) on body weight gain from days 0 to 30 of pregnancy, 1201, 287 and 438 g per day for groups HHH, LLL and LHL respectively. The pregnancy rate at day 34 was significantly higher (P<0.005) in HHH-group (100%) compared with LLL (25%) and LHL (38%) although HHH group had significantly lower (P<0.05) progesterone concentration on days 9 and 12. The basal LH level was significantly higher (P<0.01) in HHH group compared to LHL group (mean±S.D.) (0.98±0.22 and 0.60±0.08, respectively). Gilts in HHH group had a significantly higher mean LH concentration (1.18±0.24) than those in group LHL (0.7±0.07) (P<0.05), but not in group LLL (0.93±0.15) (P=0.09). There was a tendency (P=0.058) for amplitude to be higher for gilts in HHH group. The LHL feeding strategy did not provide the benefits anticipated. Instead, it was the HHH feeding strategy that provided a disfinct advantage in pregnancy rate. The mechanism mediating supportive effect of high feeding level on the maintenance of early pregnancy is yet to be determined.     

Fetal and placental weight relationships in the albino rat near term.

The relationship of fetal weight to placental weight was examined in 34 albino rats on day 22 of gestation. The influence of maternal weight, fetal position and the number of fetuses in the litter and each uterine horn were assessed also. There was no indication that rats with heavier placentas had heavier or lighter fetuses. However, within each litter, placental weight was weakly correlated (r = 0.297, p less than 0.01) with fetal weight. Maternal weight at mating, although positively related to the number of corpora lutea, was not related to mean fetal or placental weight. The number of fetuses in the litter was negatively related to placental weight but there was no apparent relation to fetal weight. Fetuses and placentas at the ovarian end of the horn were significantly lighter than those at the vaginal end. The strength of the fetal weight:placental weight correlation in the rat is compared to those in other species.     

Donor and recipient ewe factors affecting in vitro development and post-transfer survival of cultured sheep embryos

Donor and recipient factors were assessed during development of embryos following superovulation, collection at the pronuclear and two-cell stage, culture in Synthetic Oviduct Fluid medium for 5 days and twin transfer into synchronised recipients to elucidate what factors affect embryo development and post-transfer survival. In particular, the administration of exogenous progesterone to recipients using an intravaginal CIDR^TM device immediately following embryo transfer was investigated.

From 138 embryos collected from 30 donor ewes, 75% (103) were of transferable quality following culture, of which 100 were transferred to 50 recipients. There was significant variation (P < 0.001) in embryo development to the blastocyst stage between different donor ewes, but this was not related to the donor ovulation rate. At ultrasound sonography (approximately Day 60 of pregnancy), 58% of recipients were pregnant and 42% embryos had survived. Donor ovulation rate was related to embryo survival (P < 0.05) after transfer; the survival rate of embryos from ewes with high ovulation rates was lower than that of embryos from ewes with low ovulation rates. Exogenous progesterone supplementation following transfer did not affect embryo survival, rate of embryo development or plasma progesterone levels. In general, the results from this study suggest that factors other than efficacy of embryo culture can affect the outcome of embryo survival following transfer and that, where possible, these factors should be considered and balanced in experimental designs.     

Effect of strategic supplementation with multi-nutrient urea molasses blocks on body weight and body condition score of Lohi sheep owned by tenants of Pakistan

The effect of strategic supplementation with multi-nutrient urea molasses blocks (MNUMB) on BW and body condition score (BCS) in Lohi ewes (treated, n = 514) during late gestation and lactation was compared with those (control, n = 391) grazing on only post-harvest crop residues and road side in the irrigated district of Okara in central Punjab (Pakistan). Analysis of variance revealed highly significant (P < 0.01) differences in body weight (BW) and body condition score (BCS) of ewes of various ages with different reproductive status and seasons under both flocks. Analysis of variance also revealed a significant interaction (P < 0.05) between reproductive status and seasons in favor of BCS. Ewes aged 48 months in average constituted the highest (34.5% and 35.6%), whereas those aged 60 months had the smallest (10% and 4%) proportion in the control as well as in the treated flock. Mean BW and BCS in ewes of control flock was 33.5 and 2.08 kg, and lower (P < 0.05) than 35.0 and 2.31 in ewes in the treated flock, respectively. Ewes aging 12, 24 and 36 months treated with strategic supplementation of MNUMBs were not only heavier (P < 0.01) but also had highest BCS of 2.34. Lactating ewes constituted highest proportion (39%, 51%) followed by pregnant (35%, 32%) ewes in both flocks, respectively. Proportion of dry (16%) and freshly conceived (9.5%) ewes tended to be higher in the control than in the treated flock. BW was 8–11% higher (P < 0.01) in pregnant than in lactating or dry ewes in both flocks with similar BCS. Seasons of autumn and summer were found to affect BW more (P < 0.01) than BCS. Pregnant ewes in treated flocks had gained highest BW, 10–12% higher than ewes under control (P < 0.01) or than non-pregnant ewes (P < 0.05) but lost at a rate of 5–6% at lambing. BW in lactating ewes in treated flock was higher (P < 0.01) than ewes in control. Lambs suckling ewes with strategic supplementation of MNUMBs grew at a faster rate (122 g/day) with 10–15% higher survival rate than those (97 g/day) in the control flock during lactation of 16 weeks but non-significantly. Based on this improvement it can be concluded that supplementation with appropriate sources of energy and N exerts desirable effects on the traits of economic importance in sheep.     

Pregnancy diagnosis and assessment of fetal numbers in the ewe in a commercial setting

Jugular plasma progesterone concentrations were used to accurately predict open ewes (96 +/- 3%) in early pregnancy, but they less accurately predicted subsequent lambing especially during the late breeding season and most of the seasonal anestrus. Progesterone values clearly indicated that 500 I.U. of P.M.S.G. elevated ovulation rate in synchronized ewes, but did not clearly indicate fetal numbers. During late pregnancy (88-108 days), abdominal palpation, doplar ultrasound and serum progesterone analysis were equally efficacious in predicting lambing (86 +/- 9.8%, 90 +/- 9.0% and 87 +/- 4.1%, respectively), but a high percentage of ewes lambed that were diagnosed as nonpregnant (30 +/- 15.0%, 48 +/- 17.3% and 25 +/- 8.4%, respectively). Accuracy of the serum progesterone test improved the later the test was performed, although considerable individual overlap existed. Progesterone values for ewes bearing 1, 2, or greater than 2 fetuses at 94 to 95 days of gestation differed (5.5 +/- 0.3, 8.0 +/- 0.4 and 12.4 +/- 2.1, respectively (P < 0.05), whereas at 103 to 108 days values for ewes carrying two or more fetuses did not differ.     

Effect of immunization against progesterone on oestrus, cycle length, ovulation rate, luteal regression and LH secretion in the ewe

The effects of active immunization against progesterone on reproductive activity were studied in Merino ewes. Immunization against progesterone caused a shortening (P less than 0.01) of the interval between ovulations from 17-18 days (controls) to between 6 and 10 days (immunized group); this was associated with a corresponding reduction in the interval between LH surges. The immunized ewes also had higher (P less than 0.05) ovulation rates (1.72) than controls (1.25) and exhibited a reduced (P less than 0.01) incidence of oestrus (26% v. 95%). Many immunized ewes continued to ovulate despite the persistence of corpora lutea from earlier ovulations which led to an accumulation on the ovaries of many corpora lutea of different ages. The frequency of LH pulses in ewes immunized against progesterone (1.8 +/- 0.2 pulses/4 h) was significantly (P less than 0.001) higher than that of control ewes (0.3 +/- 0.1 pulses/4 h). This study highlights the importance of progesterone in the control of oestrus, ovulation, ovulation rate, luteal regression and the secretion of LH in the ewe.     

Functional anatomy of the ovaries of pregnant and lactating Cape porcupines, Hystrix africaeaustralis

The constituent cell types of the ovary of the porcupine were similar to those of New World hystricomorph rodents and accessory corpora lutea and luteal bodies were formed through the luteinization of the membrana granulosa or theca interna of antral follicles. All luteal bodies were histologically similar. The total volume of luteal tissue per female was not affected by fetal age and was unrelated to circulating concentrations of maternal plasma progesterone. Maternal plasma progesterone concentrations were correlated with fetal age. Follicular activity occurred throughout pregnancy but was not affected by fetal age or related to circulating values of oestradiol-17 beta. The formation of accessory corpora lutea during pregnancy is regarded as important in supplementing progesterone during pregnancy.     

Ovine estrus synchronization and superovulation using norgestomet B and follicle stimulating hormone-pituitary

Finewooled Rambouillet range ewes were used in a study to determine the feasibility of using a progesterone ear implant to synchronize estrus. In addition, some of the ewes were further treated with injections of follicle stimulating hormone-pituitary (FSH-P) to induce superovulation. Five days following estrus detection and breeding, FSH-P-treated ewes were laparotomized and surgically flushed to recover embryos. The number of corpora lutea (CL), the total number of embryos and the number of transferable embryos recovered were recorded along with the number and size of follicles present on both ovaries. Ewes synchronized as recipients were laparotomized for surgical transfer of embryos 5 d following estrus. The number of CL and follicles were recorded. Response to superovulation by FSH-P did not differ (P>0.05) between age groups of ewes when the number of CL present was counted. However, the total number of embryos flushed and good embryos was lower (P<0.05) among the oldest (7 yr) ewes. The number of follicles present showed little variation between age groups. Recipient ewes (No FSH-P) were similar in the number of CL with 6-yr-old ewes, having fewer (P>0.05) CL, than 3-, 4- or 7-yr-old ewes. Only slight variation was boserved in the number of follicles in recipient ewes. Among donor ewes receiving FSH-P in addition to Synchro-Mate B, 71% were detected in estrus within 48 h of implant removal vs 55% of the recipients.     

Chronic alterations in ovine maternal corticosteroid levels influence uterine blood flow and placental and fetal growth

Previous work from this laboratory demonstrated that the elevation of maternal plasma corticosteroid concentrations during pregnancy is important for the support of fetal development. Reducing ovine maternal plasma cortisol concentrations to nonpregnant levels stimulates homeostatic responses that defend fetal blood volume. The present study was designed to test the hypothesis that chronic decreases or increases in maternal plasma cortisol concentration alter uterine and placental blood flow and morphology. Three groups of pregnant ewes and their fetuses were chronically catheterized and studied: ewes infused with cortisol (1 mg.kg(-1).day(-1); high cortisol), ewes adrenalectomized and underreplaced with cortisol (0.5 mg.kg(-1).day(-1); low cortisol), and control ewes. The normal increment in uterine blood flow between 120 and 130 days was eliminated in the low-cortisol ewes; conversely, uterine blood flow was increased in the high-cortisol group compared with the control group. Fetal arterial blood pressure was increased in the high-cortisol group compared with controls, but there was no increase in fetal arterial pressure from 120 to 130 days of gestation in the low-cortisol group. The fetuses of both low-cortisol and high-cortisol groups had altered placental morphology, with increased proportions of type B placentomes, and overall reduced fetal placental blood flow. The rate of fetal somatic growth was impaired in both low-cortisol and high-cortisol groups compared with the fetuses in the intact group. The results of this study demonstrate that maternal plasma cortisol during pregnancy is an important contributor to the maternal environment supporting optimal conditions for fetal homeostasis and somatic growth.     

Receptors for prostaglandins F2 alpha and E2 in ovine corpora lutea during maternal recognition of pregnancy.

Plasma membrane receptors for prostaglandins (PG) F2 alpha and E2 were quantified in ovine corpora lutea obtained from nonpregnant and pregnant ewes on Days 10, 13, and 15 post-estrus, and from additional ewes on Days 25 and 40 of pregnancy. Regardless of reproductive status or day post-estrus, concentrations of luteal receptors for PGF2 alpha were 7- to 10-fold greater than those for PGE2. In pregnant ewes the concentration of receptors for PGF2 alpha was highest on Day 10 (35.4 +/- 2.8 fmol/mg) and lowest on Day 25 (22.3 +/- 2.5 fmol/mg). A difference in the concentration of luteal receptors for PGF2 alpha between pregnant and nonpregnant ewes was apparent only on Day 15 post-estrus, at which time the concentration of receptors for PGF2 alpha was higher in pregnant ewes than in nonpregnant ewes (27.1 +/- 2.7 vs. 17.7 +/- 2.7 fmol/mg). Concentrations of receptors for PGE2 in pregnant ewes were similar (p > 0.05; 2.8 +/- 0.3 to 3.7 +/- 0.2 fmol/mg) between Days 13 and 40 but were higher (p < 0.05) than in corpora lutea obtained from nonpregnant ewes on Days 10 (5.0 +/- 0.4 vs. 4.1 +/- 0.2 fmol/mg) and 15 (3.7 +/- 0.2 vs. 2.0 +/- 0.4 fmol/mg) post-estrus. Although concentrations of receptors for both PGF2 alpha and PGE2 were lowest in corpora lutea obtained from nonpregnant ewes on Day 15, this was not due to luteal regression since the weights and concentrations of progesterone in corpora lutea on Day 15 were not lower than those for corpora lutea obtained on Days 10 and 13.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of prostaglandin F2 alpha (PGF2 alpha) on sources of progesterone and pregnancy in intact, ovariectomized and hysterectomized 90-100 day pregnant ewes.

A single dose of 8 or 16 mg of PGF2 alpha per 58 kg body weight was injected intramuscular into intact, ovariectomized or hysterectomized 90-100 day pregnant sheep in three separate experiments. Both doses of PGF2 alpha decreased the weights of the corpora lutea (P less than or equal to 0.05) and the concentration of progesterone in ovarian venous plasma at 72 hr (P less than or equal to 0.05) compared to the 0 hr sample within treatment groups and to control ewes at 72 hr in intact and hysterectomized pregnant ewes. In hysterectomized pregnant ewes, progesterone in jugular plasma declined (P less than or equal to 0.05) from 0 to 72 hr but never fell below 4 mg/ml and this decrease in progesterone after 8 or 16 mg PGF2 alpha was greater than in control hysterectomized ewes (P less than or equal to 0.05). There was a significant decrease in progesterone over time in jugular or uterine venous plasma in the presence of absence of the ovaries in 90-100 day pregnant ewes (P less than or equal to 0.05) but the profiles of progesterone were not different between vehicle and PGF2 alpha-treated ewes (P greater than or equal to 0.05). Uterine venous progesterone never declined below 30 ng/ml in the presence or absence of the ovaries and there was a significant quadratic increase (P less than or equal to 0.05) in uterine venous progesterone toward the end of the 72 hr sampling period indicating an increase in steroidogenic activity of the placenta. PGF2 alpha did not affect the number of abortions in intact or ovariectomized pregnant ewes (P greater than 0.05). Thus, the corpus luteum of sheep at 90-100 days of pregnancy is functional and responsive to PGF2 alpha, placentomes are functional but do not appear to be responsive to the doses of PGF2 alpha tested and PGF2 alpha was not an abortifacient over the 72 hr treatment period.     

Influence of the fetal pituitary-adrenal axis on fetal and maternal progesterone and unconjugated oestrogen concentrations in the pig

Fetal and maternal plasma progesterone and unconjugated oestrone and oestradiol-17 beta concentrations were measured in intact pig fetuses and those in which the pituitary had been destroyed. Progesterone concentrations were significantly higher (P less than 0.05) and oestrogen concentrations significantly lower (P less than 0.01) in hypophysectomized fetuses than in intact fetuses. When fetuses in one uterine horn only were hypophysectomized, oestrogen concentrations in the uterine vein draining this horn were lower than those from the contralateral vein. The results indicate that both fetal and maternal oestrogen concentrations are influenced by the fetal pituitary. When dexamethasone was infused (at 27 micrograms/h for 96 h) into 5 chronically-catheterized hypophysectomized fetuses no changes in peripheral fetal progesterone or oestrone were observed.     

Induction of labour in sheep by inhibition of 3-beta hydroxysteroid dehydrogenase: role of the fetal adrenal.

In sheep parturition may be induced within 33 h in late gestation by inhibiting progesterone production with the 3 beta hydroxysteroid dehydrogenase inhibitor Epostane. Its effect has now been investigated in ewes carrying adrenalectomised (n = 5), hypophysectomised (n = 4) or intact (n = 5) fetuses to determine the role of the fetal adrenal during this type of maternally-induced delivery. Epostane was infused i.v. (1.5 mg/kg) into each group of ewes at 137-156 days gestation. Fetus and mother were sampled from the time of administration until delivery. Measurements of plasma ACTH, cortisol, progesterone and PGF2 alpha metabolite (PGFM) were made and intrauterine pressure was monitored. Epostane induced delivery significantly later in the adrenalectomised (44 h) and hypophysectomised (52 h) animals compared with the controls (33 h). The drop in maternal plasma progesterone was similar in all 3 groups, but the subsequent increases in arterial and uterine venous PGFM were smaller in the adrenalectomised and hypophysectomised ewes than in the controls. The large escalation in fetal plasma cortisol before birth in controls was absent in adrenalectomised and hypophysectomised fetuses. The slight rises in plasma cortisol observed in the latter from about 24 h after Epostane, were related to the concomitant increases in maternal plasma levels (r = 0.76, P less than 0.01). No fetuses became hypoxic or acidotic during the period of induction despite the prolonged labour of hypophysectomised and adrenalectomised fetuses.(ABSTRACT TRUNCATED AT 250 WORDS)