Uterus Of Ewes Research Articles

Incorporation of L-Carnitine in the OvSynch protocol enhances the morphometrical and hemodynamic parameters of the ovarian structures and uterus in ewes under summer climatic conditions

Heat stress negatively impacts the reproductive performance of sheep including the efficiency of estrous synchronization regimens. This study aimed to investigate the potential effects of L-Carnitine (LC) administration on the efficacy of the OvSynch protocol in ewes under summer climatic conditions. Ewes were synchronized for estrus using the OvSynch protocol and a dose of LC (20 mg/kg body weight) was intravenously (IV) administered on the same day of PGF2α injection to one group (n = 8; LC group), while other ewes (n = 8; control group) received the same protocol without LC. Ultrasonographic evaluation (including B-mode, color, and pulsed Doppler) was used to assess the morphometrical and hemodynamic parameters of ovarian structures [number, size, and blood flow of follicles (GFs) and corpora lutea (CLs)] and uterus during the estrous phase (Day 0), and on Day 8 post ovulation (luteal phase). Uterine artery blood flow (MUA) was assessed by measuring the resistive index (RI) and pulsatility index (PI) at both stages. The serum samples were collected to measure the concentrations of estradiol (E2), progesterone (P4), and total antioxidant capacity (TAC) using commercial kits. Results revealed a significant (P<0.05) increase in the colored pixel area of GFs and uterus in the LC group (392.84 ± 31.86 and 712.50 ± 46.88, respectively) compared to the control one (226.25 ± 17.74 and 322 ± 18.78, respectively) during Day 0. Circulating E2 and TAC levels were significantly (P<0.05) higher in the LC-treated ewes (31.45 ± 1.53 pg/ml and 1.80 ± 0.13 mM/L, respectively) compared to those in the control ewes (21.20 ± 1.30 pg/ml and 0.98 ± 0.09 mM/L, respectively) during Day 0. Moreover, LC improved the colored pixel area of CLs (2038.14 ± 102.94 versus 1098 ± 82.39) and uterus (256.38 ± 39.28 versus 121.75 ± 11.36) and circulating P4 (2.99 ± 0.26 ng/ml versus1.67 ± 0.15 ng/ml) on Day 8. Values of RI of MUA were significantly lower in the LC group compared to the control one on Day 0 and Day 8 (0.48 ± 0.03 versus 0.72 ± 0.03 and 0.58 ± 0.03 versus 0.78 ± 0.02, respectively). In conclusion, LC incorporation in the OvSynch protocol enhanced the morphometrical and hemodynamic parameters of the ovarian structures and the uterus concomitantly with improvements in the TAC, E2, and P4 concentrations in ewes under hot summer conditions.

Plasminogen activator activity and plasminogen activator inhibition in the uterus of ewes after the induction of oestrus synchronization or superovulation, involving eCG

During the preimplantation period, early mammalian embryos largely depend on uterine environment. Concurrently, uterine architecture undergoes substantial growth and remodeling under the influence of ovarian steroids. Plasminogen activators/plasmin proteolytic system that is implicated in tissue remodeling is affected by reproductive hormone variations. Thus, hormone treatments for reproductive function control possibly influence proteolytic enzyme activity in the reproductive tract and its study in uterine fluid and endometrium could demonstrate possible changes in uterine environment. This work examines (a) the effect of hormone treatment involving eCG in the dosage used for oestrus synchronization or for superovulation on plasminogen activator activity (PAA) and plasminogen activator inhibition (PAI) in the uterus of ewes before maternal recognition of pregnancy and (b) the possible relationships among blood ovarian steroid concentration, proteolytic enzyme activity and ovarian response/embryo yield. Chios ewes (n = 24) were treated with progestagen intravaginal sponges for 12 days and eCG (500 or 1000 IU) at sponge removal; ewes at the second oestrus after synchronization were used as controls. On day 6 of the oestrous cycle, after slaughter, ovarian response was assessed and embryos were collected; uterine horn flushings (UHF), caruncular endometrium (CE) and intercaruncular (ICE) endometrium samples were collected, for PAA and PAI photometrical assessment. Oestradiol-17β (E2) and progesterone (P4) concentration was assessed in blood serum samples collected before slaughter by a radioimmunoassay. A significant increase of PAA in the UHF was observed after treatment; PAA in UHF was significantly associated with the number of embryos or high-quality embryos, while PAA in UHF per embryo or high-quality embryo was not affected by treatment. No significant effect of treatment was noticed on PAA or PAI in the endometrium (CE, ICE). In UHF and in ICE, PAI against tissue-type PA had a significant positive relationship with PAI against urokinase-type PA. PAI against tissue-type PA in CE had significant negative relationship with E2 concentration. In conclusion, hormone treatment involving eCG in the dosage used for superovulation and, to a lesser degree, in the dosage used for oestrus synchronization affected PAA in the uterus of Chios ewes, before maternal recognition of pregnancy, but did not seem to disturb reproductive function.

Blood pressure in the chronically hypoxaemic fetus is regulated by α-adrenergic receptors on the peripheral vasculature.

Blood pressure in the chronically hypoxaemic fetus is regulated by α-adrenergic receptors on the peripheral vasculature.

Effect of using Bone Marrow Stromal Cells on Uterine Involution in Iraqi Ewes

During involution the uterus in ewes undergoes a clear remodeling; unfortunately, information on cellular and molecular activities that controls this interval is inadequate. The working hypothesis of this study applied in, is that uterus returns to a non-pregnant status during involution, involves the proliferative and regeneration activity of mesenchymal stem cells (MSCs) which migrated to the uterus servomechanism that regulates and remodeling endometrial gland epithelial surface postpartum. The present study consist of 15 Iraqi local breed ewes were divided equally into three groups. The 1st and 2nd group were injected intravenously with bone marrow stromal cells (BMSCs) in a doses 1×108, 2×108 respectively, 48 hours postpartum, while the 3rd group served as a control group. Uterine biopsy were taken at 7, 15, 17 and 21 days postpartum, and processed to histopathological examination. The progressive of involution was clearly observed in treated groups till ended at days 21 for 2nd group, as well as in the 1st group but in a lesser extent. It was concluded that BMSCs has a beneficial effect on uterine involution which is completed at day 21in Iraqi ewes.

Elongation and gene expression in bovine cloned embryos transferred to temporary recipients

SummaryElongated embryos provide a unique source of information about trophoblastic differentiation, gene expression and maternal-embryonic interactions; however they are difficult and costly to obtain, especially elongated cloned embryos. One alternative is their production in heterologous temporary recipients such as sheep and goats. We aimed to produce elongated bovine cloned embryos using heterologous transfer to temporary recipients. Day-7 cloned cattle blastocysts were transferred to the uteri of ewes and goats and recovered as elongated structures at day 17. We evaluated elongation, length, presence of embryonic disc and expression of several important genes for embryonic development. We also produced homologous (cloned cattle embryos transferred into cattle uteri). Cloned bovine blastocysts were able to proceed with preimplantation development through elongation with high efficiency despite the species to which they were transferred. In qualitative and quantitative RT-PCR experiments we found differences in the pattern of gene expression among embryos recovered from different species. Sox2, Nanog and FGF-4 were markedly deregulated. No previous reports about the expression pattern of the studied genes had been published for elongated bovine cloned embryos produced in intermediate recipients, furthermore, the pattern of expression of Nanog, Oct4, Eomes, Cdx2, IFN-tau, Dicer, FGF-4 and Sox2 shown here are novel for elongated cloned bovine embryos created by hand-made cloning. Our data confirmed that sheep and goats can be used as temporary recipients. This model could serve as a basis for further research on gene expression and cellular changes during bovine peri-implantation development.

Expression of Interferon (IFN)-Stimulated Genes in Extrauterine Tissues during Early Pregnancy in Sheep Is the Consequence of Endocrine IFN-τ Release from the Uterine Vein

The ruminant conceptus synthesizes and secretes interferon (IFN)-tau, which presumably acts via an intrauterine paracrine mechanism to signal maternal recognition of pregnancy. The aims of this study were to determine whether IFN-stimulated genes (ISG) such as ISG15 and OAS-1 are differentially expressed in blood cells circulating in the uterus of ewes; whether extrauterine components of the reproductive tract such as the corpus luteum (CL) also express mRNA for these ISG, and whether antiviral activity is greater in uterine vein than in uterine artery during early pregnancy. The concentrations of mRNA for both ISG were significantly greater (P < 0.0001) in endometrium and jugular blood of 15-d pregnant ewes than in nonpregnant ewes. ISG15 and OAS-1 mRNA concentrations were also greater (P < 0.05) in CL from 15-d pregnant ewes than in nonpregnant ewes. Immunohistochemistry revealed intense staining for ISG15 in large luteal cells on d 15 of pregnancy. Blood cells from uterine artery and vein of 15-d pregnant ewes had similar ISG15 and OAS-1 mRNA concentrations, suggesting that these cells were not conditioned by IFN-tau within the uterus. By using an antiviral assay, uterine venous blood was found to contain 500- to 1000-fold higher concentrations of bioactive IFN-tau than in uterine arterial blood on d 15 of pregnancy. It is concluded that uterine vein releases IFN-tau, which induces ISG in extrauterine tissues such as the CL during the time of maternal recognition of pregnancy.

Effects of Gram-positive bacterial pathogens in ewes: peptidoglycan as a potential mediator of interruption of early pregnancy

Bacterial cell walls contain peptidoglycan (PTG), which, among other actions, induces fever. The present experiment evaluated the effects of PTG treatment on early pregnancy and blood plasma concentrations of reproductive hormones. Ewes were injected i.v. with saline or 15, 30 or 60 microg kg(-1) sonicated PTG (Streptococcus pyogenes) on day 5 after mating. Each dose of PTG induced fever. Pregnancy rate at day 25 was not related to incidence of fever but tended to differ among treatments (control, 100%; low, 100%; medium, 67%; high, 60%; P < 0.08). Combined pregnancy rate in ewes from control and low dose groups (100%) was greater than that in ewes from medium and high dose groups (64%, P < 0.01). Ewes with high 13,14-dihydro-15-keto-prostaglandin F(2alpha) (PGFM) concentrations had lower pregnancy rates (6 of 10) than those with low concentrations of PGFM (11 of 11; P < 0.05). Mean cortisol concentrations were higher in treated (2.8 +/- 0.28 microg dl(-1)) than in control (1.1 +/- 0.03 microg dl(-1)) ewes (P < 0.01); the pattern of secretion was biphasic and increased in all treated ewes (P < 0.01). Neither means nor profiles of oestradiol differed with treatment. Mean concentrations and the pattern of concentrations of progesterone were reduced in all treated ewes, as indicated by the time by treatment and linear interaction with treatment (1.2 +/- 0.1 versus 1.6 +/- 0.1 ng ml(-1), P < 0.01). Patterns of LH pulses did not differ from 0 to 4 h or 24 to 28 h after treatment; mean plasma LH concentration was lower in ewes treated with 0, 15 or 30 microg PTG kg(-1) than with 60 microg PTG kg(-1) (P < 0.01). Pregnancy status was not related to plasma concentrations or patterns of LH, oestradiol, progesterone or cortisol. Inflammatory mediators, such as PGF(2alpha), may act directly on the embryo or uterus in ewes treated with PTG.

Effects of Gram-positive bacterial pathogens in ewes: peptidoglycan as a potential mediator of interruption of early pregnancy

Bacterial cell walls contain peptidoglycan (PTG), which, among other actions, induces fever. The present experiment evaluated the effects of PTG treatment on early pregnancy and blood plasma concentrations of reproductive hormones. Ewes were injected i.v. with saline or 15, 30 or 60 microg kg(-1) sonicated PTG (Streptococcus pyogenes) on day 5 after mating. Each dose of PTG induced fever. Pregnancy rate at day 25 was not related to incidence of fever but tended to differ among treatments (control, 100%; low, 100%; medium, 67%; high, 60%; P < 0.08). Combined pregnancy rate in ewes from control and low dose groups (100%) was greater than that in ewes from medium and high dose groups (64%, P < 0.01). Ewes with high 13,14-dihydro-15-keto-prostaglandin F(2alpha) (PGFM) concentrations had lower pregnancy rates (6 of 10) than those with low concentrations of PGFM (11 of 11; P < 0.05). Mean cortisol concentrations were higher in treated (2.8 +/- 0.28 microg dl(-1)) than in control (1.1 +/- 0.03 microg dl(-1)) ewes (P < 0.01); the pattern of secretion was biphasic and increased in all treated ewes (P < 0.01). Neither means nor profiles of oestradiol differed with treatment. Mean concentrations and the pattern of concentrations of progesterone were reduced in all treated ewes, as indicated by the time by treatment and linear interaction with treatment (1.2 +/- 0.1 versus 1.6 +/- 0.1 ng ml(-1), P < 0.01). Patterns of LH pulses did not differ from 0 to 4 h or 24 to 28 h after treatment; mean plasma LH concentration was lower in ewes treated with 0, 15 or 30 microg PTG kg(-1) than with 60 microg PTG kg(-1) (P < 0.01). Pregnancy status was not related to plasma concentrations or patterns of LH, oestradiol, progesterone or cortisol. Inflammatory mediators, such as PGF(2alpha), may act directly on the embryo or uterus in ewes treated with PTG.

Expression of endogenous betaretroviruses in the ovine uterus: effects of neonatal age, estrous cycle, pregnancy, and progesterone.

The ovine genome contains 15 to 20 copies of endogenous retroviruses (enJSRVs) highly related to the oncogenic jaagsiekte sheep retrovirus (JSRV) and enzootic nasal tumor virus. enJSRVs are highly expressed in the endometrial lumenal epithelia (LE) and glandular epithelia (GE) of the ovine uterus. The effects of neonatal age, estrous cycle, pregnancy, and progesterone on expression of enJSRVs in the ovine uterus were determined. Expression of enJSRV RNAs was absent from the uterus of ewes at birth, but enJSRV RNAs were expressed specifically in the LE and developing GE from postnatal day (PND) 7 to PND 56. In adult ewes, enJSRV RNAs were detected only in the epithelia of the uterine endometrium, as well as epithelia of the oviduct, cervix, and vagina. In cyclic ewes, endometrial enJSRV RNA abundance was lowest on day 1, increased 12-fold between days 1 and 13, and then decreased to day 15. In pregnant ewes, levels of endometrial enJSRV RNAs were high on day 11, increased to day 13, and then decreased to day 19. In day 17 and 19 conceptuses, enJSRV RNAs were also detected in binucleate cells of the trophectoderm. Immunoreactive JSRV capsid and envelope proteins were detected in the endometrial LE and GE, as well as in the binucleate cells of the conceptus. In transfection assays utilizing ovine endometrial LE cells, progesterone increased transcriptional activity of several enJSRV long terminal repeats. Collectively, these results indicate that transcription of enJSRVs in the endometrial epithelia of the ovine uterus is increased by progesterone and might support a role for enJSRVs in conceptus-endometrium interactions during the peri-implantation period and early placental morphogenesis.

The ovine uterus as a host for in vitro-produced bovine embryos

A series of experiments were conducted to determine whether bovine blastocysts would develop beyond the blastocyst stage in the ovine uterine environment. In Experiment 1, in vitro matured, fertilized and cultured (IVM/IVF/IVC) expanded bovine blastocysts were transferred into uteri of ewes on Day 7 or 9 of the estrous cycle and collected on Day 14 or 15 to determine if the bovine blastocysts would elongate and form an embryonic disk. Springtime trials with ewes that were synchronized with a medroxyprogesterone acetate (MAP) sponge resulted in a 78% blastocyst recovery rate, and 68% of the recovered spherical or elongated embryos had embryonic disks. In Experiment 2, transfer of 4-cell bovine embryos to the oviducts of ewes at Day 3 resulted in a lower recovery (47 vs 80%) than the transfer of blastocysts at Day 7 when embryos were recovered at Day 14. However, the percentage of embryos containing embryonic disks was higher for embryos transferred at the 4-cell stage (71%) than for embryos transferred as blastocysts (50%). In Experiment 3, IVF embryos from super-ovulated cows or Day 8 in vitro produced embryos transferred to cows were collected at Day 14 and were found to be similar in size to those produced by transfer to ewes in Experiment 2. In Experiment 4, the transfer of bovine blastocysts to ewes did not prolong the ovine estrous cycle. In Experiment 5, extension of the ovine estrous cycle by administration of a MAP releasing intravaginal device allowed bovine embryos to elongate extensively and to become filamentous. In Experiment 6, uterine flushings on Day 14 or Day 16 contained elevated levels of interferon-tau when bovine blastocyst were transferred on Day 7. Transfer of bovine embryos to the reproductive tract of a ewe allows some embryos to develop normally to advanced perimplantation stages and may be a useful tool for studying critical stages of embryo development and the developmental capacity of experimental embryos.

Effect of undernutrition on the distribution of progesterone in the uterus of ewes during the luteal phase of the estrous cycle

The effect of undernutrition on ovarian and uterine venous progesterone concentrations and endometrial progesterone content on Days 5 and 10 of the estrous cycle were studied. Forty ewes were synchronized using progestagen pessaries. At pessary withdrawal, the ewes were fed diets to provide either 1.5 or 0.5 times the daily maintenance requirement (Group H, n=20 and Group L, n=20, respectively). Ewes fed the low nutrition diet (Group L) had higher mean peripheral progesterone concentrations than those fed the high plane diet (Group H; P<0.05) but lower endometrial progesterone content on Day 5 (P<0.05). Neither ovarian nor uterine venous levels were affected by nutrition on either Day 5 or 10. Progesterone concentrations in blood samples collected ipsilateral to ovaries bearing a corpus luteum (CL) were higher than in the contralateral samples (P<0.001). It is concluded that undernutrition can produce a reduction of endometrial content of progesterone the first week after mating. Since no differences in ovarian venous concentrations were observed, it remains to be shown whether this variation is due to other variables, such as the population of endometrial progesterone receptors or other nonhormonal factors.

Cervical dilation with exogenous oxytocin does not affect sperm movement into the oviducts in ewes

Exogenous oxytocin aids in the transcervical passage of an AI gun into the uterus of ewes, and it may be an effective adjunct to sheep AI procedures. However, the effects of oxytocin on sperm transport and fertility are unclear. Thus, experiments were conducted to evaluate the effects of oxytocin on variables that may affect fertility. In Experiment 1, five ewes/group received intravenous injections of 0, 50, 100, 200 or 400 USP units of oxytocin. Oxytocin enhanced (P < 0.001) uterine entry; the rates were 0% for control, 60% for the 50- and 100-unit doses, and 100% for the 200- and 400-unit doses. In Experiment 2, five ewes/group received intravenous injections of 0, 50, 100, 200, or 400 USP units of oxytocin, and the effect on uterine contractions was observed with a laparoscope. Oxytocin induced myometrial tetany within 2 min. The dose affected (P < 0.05) the duration of tetany, which was 0, 21, 27, 29, and 41 min for the 0-, 50-, 100-, 200- and 400-unit doses, respectively. In Experiment 3, either 0 or 200 USP units of oxytocin were injected intravenously 52 h after removal of progestogen pessaries from 20 ewes. Ewes were inseminated laparoscopically 10 min later with fresh, extended semen (500 × 10 6 sperm cells) into the right uterine horn. Ewes were slaughtered 20 h after AI, and the numbers of spermatozoa were determined. Oxytocin did not affect (P > 0.05) the movement of spermatozoa throughout the uterus and into both oviducts. In summary, oxytocin induced myometrial tetany and permitted the passage of the tip of an AI gun into the uterus. However, oxytocin did not disrupt sperm transport to the oviducts. We conclude that oxytocin-induced cervical dilation may be a useful adjunct to transcervical intrauterine AI procedures for sheep.

Embryonic survival in the uterus of ewes inseminated at the uterotubal junction on Day 32 post partum

Experiments were conducted to determine 1) if pregnancy initiated on Day 32 post partum would be maintained until lambing, 2) if there is a difference in the ability of the previously gravid or nongravid uterine horn to maintain pregnancy, and 3) if season has an effect on embryo loss. Estrus was induced in ewes on Day 32 post partum. At estrus, ewes were inseminated surgically at the uterotubal junction and assigned to the following groups: 1) inseminated at estrus and laparotomized on Day 3 to collect embryos for determination of fertilization rate (C), 2) inseminated in the previously gravid uterine horn (PG), 3) inseminated in the previously nongravid uterine horn (NG), and 4) inseminated when both horns were previously gravid (BG). Ewes pregnant in the PG, NG and BG groups were allowed to lamb. Conception rate in Group C at embryo collection was 70%. Embryo loss, based on concentrations of progesterone at Day 18 post insemination, was 43, 19 and 18% in the BG, NG and PG group, respectively. The high embryo loss in Group BG occurred only during the breeding season. Only 24% of the ewes that had been inseminated lambed. This was due to the prepartum loss of embryos and fetuses (47, 48 and 33% in Group BG, NG and PG, respectively. In conclusion, the detrimental effects of the uterus on embryo survival was evident within 18 d post insemination in Group BG (breeding season), and embryo loss prior to lambing was high in all the treatment groups (both seasons).

Effect of post-ovulation nutritional status in ewes on early conceptus survival and growth in vivo and luteotrophic protein secretion in vitro

Overfeeding during early pregnancy in ewes compromises pregnancy establishment and/or embryo survival. To determine whether high feed intakes after ovulation alter the secretory dialogue between the conceptus and the endometrium, 24 embryos (8-16-cell) from ewes fed maintenance rations were synchronously transferred in singleton on Day 3 of the cycle (oestrus, Day 0) into the uterus of ewes receiving a high or low plane of nutrition from Day 0 (n = 12 ewes per group). Embryo survival and conceptus growth were assessed on Day 16. At this time, pregnancy was maintained in 11 of 12 recipient ewes per group and conceptus mass was not influenced by nutritional plane (637 +/- 48 v. 583 +/- 72 mg for high and low groups respectively). Conceptus and endometrial tissues were cultured separately for a further 24 h in vitro in the presence of [3H]leucine. There was no quantitative difference between nutritional treatments in the incorporation of radiolabel into proteins synthesized and secreted by the conceptus or endometrium. Secretion of ovine trophoblast protein-1 was also similar in both groups. Peripheral progesterone concentrations were significantly (P < 0.05) lower throughout the luteal phase in recipient ewes on high v. low intakes after ovulation. This effect was independent of ovulation rate which was 3.1 +/- 0.40 and 2.6 +/- 0.25 corpora lutea for high and low groups respectively. A high plane of nutrition after ovulation did not influence embryo survival and development in vivo or luteotrophic protein secretion in vitro despite a reduction in peripheral progesterone concentrations.(ABSTRACT TRUNCATED AT 250 WORDS)

Co-ordination of electrical activity in the myometrium of pregnant ewes.

The co-ordination of spontaneous and evoked electromyographic (EMG) activity was examined in the uterus of ewes from Day 100 of pregnancy and during labour. During pregnancy the onset of bursts of EMG activity was synchronous to within 2-3 min when recorded by electrodes at any recording site. Individual EMG spikes, whether occurring spontaneously or evoked by electrical stimulation of the myometrium, appeared to propagate between recording electrodes that were 1-3 cm apart, in the longitudinal or circular orientation of the uterus, but not when the electrodes were separated by more than 3 cm. Apparent conduction velocity in the longitudinal orientation was 7 cm sec-1 during pregnancy and increased to 13 cm sec-1 during labour. No consistent pattern could be distinguished in the sites at which EMG activity was first observed at any stage of pregnancy studied. The nature of propagation of EMG activity remains unresolved but it is clear that it is not initiated at a single site in the myometrium.

Proportions of nucleic acids in the uteri of ewes with clover disease and the effect of oestrogen after ovariectomy.

In entire ewes, the ratio of RNA to DNA in the uterus was higher at oestrus than at dioestrus but did not differ between control and clover-affected ewes at either stage of the oestrous cycle. After ovariectomy the ratio of RNA to DNA in the uteri decreased in both control and clover-affected ewes, but the decrease was greater in the control ewes (P less than 0.01). Subsequently when ewes received a single injection of oestradiol-17 beta, a similar rise in uterine RNA/DNA ratio occurred in the two groups. However, following injection of the ewes with oestradiol-17 beta for 3 days, the ratio of uterine RNA to DNA was higher in control than in clover-affected ewes (P less than 0.05). Thus, the uteri from clover-affected ewes undergo less regression after ovariectomy and yet show less response to repeated oestrogenic stimulation that do that of control ewes. This pattern of response is consistent with the hypothesis that the permanent changes caused by phyto-oestrogens in ewes are analogous to the differentiation which normally occurs during organogenesis.

Effects of PMSG and the prostaglandin F-2 alpha analogue, cloprostenol, on superovulation, fertilization and egg transport in the ewe.

Romney ewes were artificially inseminated at the oestrus after treatment with PMSG on Day 12 of the cycle, Cloprostenol on Day 14, or both. PMSG resulted in increased numbers of ovulations and large follicles but Cloprostenol had no effect alone or with PMSG, PMSG and Cloprostenol alone led to reduced proportions of eggs fertilized, and PMSG also reduced the proportion of ewes with fertilized eggs. The distribution of eggs in the reproductive tract indicated more rapid egg transport in ewes treated with PMSG. A greater proportion of eggs was recovered from the uterus in ewes in which oestrus was first detected at night. Cloprostenol, as administered to PMSG-treated ewes in this trial, offered no advantage for the preparation of donor ewes for egg transfer.

Prostaglandin F 2α in the uterus of ewes during early pregnancy

PGF 2α has been postulated to be the uterine luteolytic factor. If this is true, then one might expect the levels of PGF 2α to be lower during early pregnancy. However, in the present study levels of PGF 2α were found to be significantly higher in both content (ng) and concentration (ng/gm) in the endometrium of day-13 pregnant ewes (2375, 152 respectively) compared to day-13 nonpregnant animals (1478, 89 respectively). These results imply that the luteotropic effects of the embryo must occur by some mechanism other than inhibition of production or release of the uterine luteolytic factor.