Anatomicohistological characteristics of the tubular genital organs of the female collared peccary (Tayassu tajacu) from North-eastern Amazon

The present study examines anatomical and histological characteristics of tubular genital organs and its relationships with the reproductive state of 24 wild adult collared peccary (Tayassu tajacu) females. The tunica mucosa of the uterine tube presents a pseudostratified, intermittently ciliated columnar epithelium. The epithelial secretory cells of pregnant females and females in the luteal phase of the oestrous cycle became taller than the ciliated cells and showed abundant apical secretory blebs, whereas secretory cells of females in the follicular phase showed abundant mucous secretory activity (periodic acid-Schiff positive cells). The uterus is composed of two narrow and convoluted uterine horns, separated by the velum uteri, a small uterine body and a long and muscular cervix. The endometrial lining of both uterine horns and body is a monostratified, columnar ciliated epithelium. Pregnant females and females in luteal phase showed a more developed hyperplasia of the endometrial simple tubular glands than females in the follicular phase. The cervix presents interdigitated rows of mucosal prominences that project into the lumen, structures similar to pulvini cervicali, occluding the cervical canal. In pregnant females, the endocervical canal was filled by a viscous cervical secretion. Females in follicular phase presented a thicker vaginal epithelium than pregnant females and females in luteal phase. The present study suggests that the collared peccary female showed different histological features of the uterine tubes, uterus and vagina in accordance with the reproductive state of the females.     

Distribution of cytosolic oestrogen and progesterone receptors in the genital tract of the mare

The distribution of oestrogen and progesterone receptors in the equine genital tract was investigated by means of a modified dextran-coated charcoal method on samples collected from the vagina, the cervix and the uterus of 30 healthy adult Polish mares, divided into two groups on the basis of their serum progesterone levels. The concentrations of oestrogen and progesterone receptors were significantly (P<0·05) lower in the vagina and the cervix than in the uterus, in agreement with data from human beings, cattle and pigs, which showed that the highest concentrations of oestrogen and progesterone receptors were localised respectively in the body and in the horns of the uterus.     

Presence of a Temperature Gradient Among Genital Tract Portions and the Thermal Changes Within These Portions Over the Estrous Cycle in Beef Cows

The aim of the present study was to describe the temperature of the different portions of the female genital tract and their relation to rectal temperature and to investigate the effect of steroid hormones profiles on these variables over the estrous cycle in cattle. Four nonpregnant Japanese Black cows were investigated daily over two successive estrous cycles using a digital thermometer with a long probe and rounded-end sensor to record the temperature of the rectum (RT), vagina (VT), cervix (CT), uterine body (UBT) and uterine horns (UHT). Blood samples were collected immediately before temperature recording to assay peripheral levels of progesterone (P₄) and estradiol-17β (E₂). Moreover, transrectal ultrasonography was carried out after temperature recording to monitor the ovulatory follicle and track ovulation. During the experiment, the ambient temperature and relative humidity were recorded for further calculation of the temperature humidity index (THI). The temperature within the genital tracts in these cows progressively increased towards the uterine horns from the vagina. The VT, CT, UBT and UHTs were significantly higher in association with peripheral P₄ concentrations greater than 4 ng/ml (mid-luteal phase) when compared with lower peripheral P₄ concentrations. The VT was more significantly (P<0.01) correlated to the CT, UBT and UHTs than RT. In conclusion, a temperature gradient was present among the vagina, cervix and uterus over the estrous cycle, and changes in peripheral P₄ concentrations were associated with the thermal variations within these portions. The VT could be more beneficial than RT in monitoring temperature of deeper portions of the female genital tract in bovine.     

Fish meal supplementation alters uterine prostaglandin F2alpha synthesis in beef heifers with low luteal-phase progesterone

The objective of the current study was to evaluate the effect of omega-3 fatty acids in fish meal on mitigating uterine PGF2alpha synthesis in heifers with low luteal-phase concentrations of progesterone. Animals were individually fed a corn silage-based diet supplemented with fish meal (5% of DMI; n = 12) or corn gluten meal (6% of DMI; n = 13). Estrous cycles were synchronized using PGF2alpha beginning on d 25 of supplementation. Random heifers from each supplement group (n = 6 fish meal, and n = 7 corn gluten meal) were given three additional i.m. injections of PGF2alpha (25 mg) at 12-h intervals beginning at 0600 on d 3 after estrus to induce formation of corpora lutea that secrete lower concentrations of progesterone. Jugular blood samples were collected daily commencing on d 1 and continuing through d 16 of the estrous cycle to determine serum progesterone concentrations. Oxytocin was administered i.v. (100 IU) to heifers on d 16 after estrus to stimulate uterine PGF2alpha synthesis. Before statistical analyses, heifers were sorted to either normal or low luteal-phase progesterone as determined from serum progesterone on d 9 of the estrous cycle. After sorting, treatment groups consisted of 1) normal luteal progesterone + fish meal (n = 6); 2) low luteal progesterone + fish meal (n = 6); 3) normal luteal progesterone + corn gluten meal (n = 6); and 4) low luteal progesterone + corn gluten meal (n = 7). Serum concentrations of the PGF2alpha metabolite following oxytocin stimulation tended (P = 0.09) to be greater in heifers with low luteal-phase progesterone compared with heifers with normal luteal-phase progesterone. Fish meal supplementation mitigated this response in heifers with low luteal-phase progesterone (P < 0.05), but had no effect on heifers with normal luteal-phase progesterone. In conclusion, the omega-3 fatty acids in fish meal seem to decrease uterine PGF2alpha synthesis in heifers with low luteal-phase serum concentrations of progesterone.     

Uterine influences on the formation of subnormal corpora lutea in seasonally anestrous ewes

The hypothesis that subnormal luteal function after induced ovulation in anestrous ewes was the result of uterine influences exerted during the periovulatory period was tested. Crossbred ewes (n = 27) in seasonal anestrus were induced to ovulate by administration of 12 doses of 250 ng of LHRH at 2-h intervals, followed immediately by a bolus injection of LHRH (250 micrograms; d 0). Ewes were unilaterally hysterectomized on either d -3 (PRELHRH) or 2 (POSTLHRH). Daily blood samples were collected and assayed for progesterone (P4) and 13,14-dihydro-15-keto-prostaglandin F2 alpha (PGFM). All ewes were slaughtered on d 10, and corpora lutea (CL) were collected, weighed, and assayed for concentration of P4. All ewes that ovulated exclusively in the ovary ipsilateral to the remaining uterine horn had a transient increase in plasma P4 of 2 to 3 d (short luteal phase). In ewes with at least one CL in the isolated ovary, elevated plasma P4 was maintained after hysterectomy but was consistently lower (P less than .05) in POSTLHRH ewes than in PRELHRH ewes. Concentrations of PGFM did not differ between treatments. The CL ipsilateral to the remaining uterine horn weighted less (P less than .01) and contained less P4 (P less than .01) than contralateral CL. These data confirm the hypothesis that premature regression of subnormal CL is uterine-dependent in a local fashion. Presence of the uterus during the follicular and(or) early luteal phase inhibited subsequent luteal function in seasonally anestrous ewes.     

Progesterone secretion by the bovine fetoplacental unit and responsiveness of corpora lutea to steroidogenic stimuli at two stages of gestation

To evaluate the response of luteal cells to in vitro stimulation with luteinizing hormone (LH) or dibutyryl cyclic adenosine monophosphate (dbcAMP) and determine the secretion of progesterone by the fetoplacental unit, the corpora lutea were removed surgically in 10 cows (luteectomy) at 250 days (5 cows) or 270 days (5 cows) of gestation. During surgery, but before luteectomy, catheters were placed in the middle uterine artery and vein, carotid artery, and jugular vein. Blood samples were collected from all catheters just before luteectomy and at 8-hour intervals after luteectomy for 72 hours or until calving, whichever occurred first. Luteal tissue was prepared as a dispersed cell preparation and incubated with 0, 0.1, 1.0, 10, or 100 ng of LH/ml of medium or was incubated with 0, 0.5, or 2 mM dbcAMP. Synthesis of progesterone in response to LH by dispersed cells prepared from corpora lutea at 270 days was less (P less than 0.01; analysis of variance) than that by similar preparations at 250 days because a dose-response relationship was not observed for incubations of luteal tissue with LH at 270 days of gestation. Progesterone synthesis in response to the addition of dbcAMP also was less (P less than 0.01) at 270 than at 250 days of gestation. This difference in responsiveness to LH and dbcAMP between the 2 stages of gestation was not reflected by a significant difference between stages of gestation in systemic concentrations of progesterone before luteectomy.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of estrone infusion on secretion of F series prostaglandins and on function of the corpus luteum during late gestation in cattle

Catheters were surgically implanted in the carotid artery, jugular vein, and middle uterine vein of 8 cows at 245 days of gestation. Four cows were given 4 mg of estrone/hour via continuous jugular infusion from 0800 hours on day 246 of gestation through 0800 hours on day 250 of gestation; the remaining 4 cows (controls) were given the vehicle for estrone at 10 ml/hour for the same period. Blood samples were collected from the carotid artery every 3 hours during the infusion. Samples were collected hourly from the middle uterine vein from 0 through 8, 54 through 66, and 112 through 120 hours of the infusion periods. After completion of the infusion, corpora lutea were enucleated and blood samples were collected from the carotid artery and uterine vein at hourly intervals for an additional 8 hours. Dispersed cell preparations of the corpora lutea were incubated with and without luteinizing hormone (LH) or dibutyryl cyclic adenosine monophosphate (dbcAMP). Circulating concentrations of unconjugated and conjugated estrone and estradiol-17 beta were higher (P less than 0.05) in the group infused with estrone than in the vehicle-infused group. Mean and base-line concentrations of F series prostaglandins (PGF) for each blood collection period tended to increase (P less than 0.10) during infusion with estrone, but not during infusion with vehicle. After luteectomy, mean and base-line concentrations of PGF also tended (P less than 0.10) to be greater in the estrone-infused cows than in the control cows, but a surge in PGF concentrations due to removal of the ovarian source of progesterone did not develop.(ABSTRACT TRUNCATED AT 250 WORDS)     

Response of plasma cortisol and progesterone after ACTH challenge in ovariectomized lactating dairy cows

Shortened and weakened estrous expressions could be one of the causes of poor heat detection rate. Non-specific acute stresses are assumed to depress expression of estrus by an increase of plasma progesterone which may originate from the adrenal cortex. The objective of the present study was to examine whether the adrenal cortex can secrete significant amounts of progesterone in response to exogenous adrenocorticotropic hormone (ACTH) in lactating cows. Four cows had estrus synchronized and were ovariectomized in the luteal phase. The cows were given 25 IU ACTH through an indwelling catheter 5 h after catheterization. Blood samples were collected at an interval of 30 min. In 3 of the 4 cows, plasma progesterone concentrations increased significantly 0.5-1.5 h after the first ACTH challenge with a mean peak value of 4.2 +/- 0.4 (S.D.) ng/ml. A similar response was also observed after the second ACTH challenge. Peak plasma progesterone concentrations in the 3 cows after first ACTH challenge were comparable with the progesterone values in the luteal phase of each cow. The results suggest that lactating cows have the capability to secrete a significant amount of progesterone from the adrenal cortex.     

First luteal tissue in ewe lambs: influence on subsequent ovarian activity and response to hysterectomy

Two experiments were conducted in peripuberal ewe lambs to determine (a) the influence of the first luteal structure [most frequently a transient (i.e., 1 to 4 d) structure] on subsequent ovarian activity and (b) a role for the uterus in its demise. In Exp. 1, 21 lambs were assigned randomly on the day of the first rise in progesterone in the plasma to (1) sham-operation, (2) removal of the nonluteal ovary, (3) removal of the luteal ovary and (4) removal of the luteal ovary plus progesterone replacement (5 mg given three times 12 h apart, initiated at surgery). No effect of treatment on subsequent ovarian activity was observed. In Exp. 2, four of 14 lambs were assigned randomly to be hysterectomized before their first rise in progesterone. The remaining 10 lambs, (five each) were sham-operated or hysterectomized on the day of the first rise in progesterone. All hysterectomized lambs (N = 9) exhibited a rise in progesterone and maintained elevated concentrations of progesterone, whereas sham-operated lambs initiated estrous cycles. Oviducts and uteri collected from lambs hysterectomized on the day of the first rise in progesterone in Exp. 2 were flushed for presence of oocytes and none were found. Similarly, no retained oocytes were found in histological preparations of first luteal structures obtained from eight lambs ovariectomized in Exp. 1. Concentrations of luteinizing hormone (LH) and prolactin were determined in daily samples collected from 19 lambs in Exp. 1. Luteinizing hormone increased and became more variable as lambs matured, whereas prolactin decreased with no detectable change in variability. It is concluded that the transient luteal structure is not required for sexual maturation and that its lifespan is uterine dependent.     

Reproductive performance of Holstein cows administered GnRH analog HOE 766 (Buserelin) 26 to 34 days postpartum

During the fourth week postpartum, 443 healthy Holstein cows milked thrice daily were randomly divided among four groups to receive 0, 2, 8 and 32 micrograms of the GnRH analog HOE 766. Intervals from calving to first estrus and to first breeding, from breeding to conception and conception rates at first breeding were calculated to measure treatment response, and progesterone was measured in the fat-free portion of milk samples collected twice weekly during the first 4 wk following treatment. Uterine involution at the time of treatment was estimated by palpation per rectum. Twenty percent of the cows examined were classified as having delayed uterine involution (abnormal). By analyzing milk progesterone patterns it was determined that 38% of the animals were in the luteal phase of an estrous cycle when treated. Cows without luteal tissue (less than 1 ng of progesterone/ml milk) given 8 or 32 micrograms of HOE 766 increased in progesterone to greater than or equal to 1 ng/ml within 7 d in 77 and 72% of the cows compared with 40 and 57% for cows receiving 0 and 2 micrograms (P less than .05). This increase in progesterone was followed by a normal estrous cycle within 4 wk in a higher proportion of cows treated with the two higher doses of GnRH analog (87 and 86%) compared with 67 and 70% of those receiving 0 or 2 micrograms of the analog (P less than .005). There were no treatment differences (P greater than .05) for other traits analyzed, but cows with a normal progesterone cycle were observed in estrus and were bred sooner (P less than .01) than those with irregular progesterone patterns. It was concluded that the GnRH analog hastened the onset of normal ovarian cycles in cows milked thrice daily.     

Epidermal growth factor and epidermal growth factor receptor immunoreactivity in the endothelial cells of the uterine artery and its branches during different stages of the estrous cycle in the pig

The uterine artery and its branches are the most important vessels that supply the uterus with blood, nutrients and active substances. Epidermal growth factor (EGF) and its receptor (EGFR) are expressed in many tissues, including reproductive organs, and is involved in angiogenesis, embryo implantation and development as well as in proliferation and differentiation of various cells. The aim of our study was to determine EGF and EGFR immunoexpression in the uterine artery and its branches during the estrous cycle in the pig. The experiment was performed on cryostat sections of the uterine artery and its branches stained immunohistochemically by ABC method. Light microscopic observations revealed the phase-related immunoreactivity of EGF and EGFR in the endothelial cells of the uterine artery and its branches. The highest intensity of EGF and EGFR immunoreaction in endothelial cells of the uterine artery was observed in the follicular phase. A significant decrease in the intensity of EGF and EGFR immunoreactivity was found in the middle luteal phase. Similar results of the immunostaining were found with regard to EGFR. In the endothelium of the uterine arterial branches, a significant increase in the intensity of EGF and EGFR-immunoreactivity was observed in the middle luteal phase. A decrease in the intensity of EGF immunostaining was observed in the late luteal phase. The phase-related expression of EGF and EGFR in the endothelium of the uterine artery and its branches suggest the modulatory effect of EGF and its receptor on the uterine artery and the region supplying these vessels.     

Inhibitory effects of CIDR-based ovulation-synchronization protocols on uterine PGF2alpha secretion at the following luteal phase in early postpartum non-cycling beef cows

We investigated whether CIDR-based ovulation-synchronization protocols inhibit secretion of prostaglandin (PG) F2alpha from the uterus in the following luteal phase in non-cycling beef cows. Ten early (a month) postpartum non-cycling Japanese Black beef cows were treated with (1) Ovsynch (GnRH analogue on Day 0, PGF2alpha analogue on Day 7, and GnRH analogue on Day 9; n=3), (2) Ovsynch+CIDR (Ovsynch protocol plus a CIDR for 7 days from Day 0; n=4), or (3) estradiol benzoate (EB) Ovsynch+CIDR (EB on Day 0 in lieu of the first GnRH treatment followed by the Ovsynch+CIDR protocol; n=3). An oxytocin challenge was administered on Day 24 to examine uterine PGF2alpha secretion. Plasma concentrations of 13,14-dihydro-15-keto- PGF2alpha were lower at 30-120 min after oxytocin administration in the Ovsynch+CIDR group and 75 min after administration in the EB Ovsynch+CIDR group than in the Ovsynch group (P<0.05). Plasma progesterone concentrations were higher from Days 1 to 7 in the Ovsynch+CIDR group and from Days 1 to 5 in the EB Ovsynch+CIDR group than in the Ovsynch group (P<0.05). The progesterone concentrations were higher on Days 27 and 29 in both CIDR-treated groups than in the Ovsynch group (P<0.05). In conclusion, in non-cycling beef cows, CIDR-based ovulation-synchronization protocols inhibit uterine PGF2alpha secretion in the following luteal phase and prevent premature luteolysis as is seen with the Ovsynch protocol.     

Uterine activity in cows during the oestrous cycle, after ovariectomy and following exogenous oestradiol and progesterone

Uterine activity was monitored in three, 2-year-old nulliparous Ayrshire heifers using intrauterine balloon-tipped catheters and pressure transducers during the oestrous cycle, after ovariectomy and following the intravenous infusion of progesterone and oestradiol-17 beta. During the oestrous cycle uterine activity, as measured by the frequency and amplitude of contractions, was greatest around oestrus and declined during the luteal phase of the cycle; there was a close correlation with peripheral progesterone concentrations. In two animals after bilateral ovariectomy spontaneous uterine activity persisted, whilst in the third animal the uterus was quiescent. In the first two heifers intravenous progesterone infusions reduced the spontaneous uterine activity, eventually completely abolishing it. There was evidence of a dose response effect at the two infusion rates. Oestradiol benzoate infusions initially inhibited spontaneous uterine activity before stimulating contractions with some evidence of a dose relationship. As demonstrated in normal cyclical and steroid-infused animals, uterine activity appears to be under the influence of both hormones although the influence of progesterone is greater.     

Effects of GnRH or progesterone treatment on day 5 post-AI on plasma progesterone, luteal blood flow and leucocyte counts during the luteal phase in dairy cows

This study was designed to test the effects of progesterone or GnRH treatment on day 5 post-AI on fertility and luteal function in dairy cows and heifers. Five days after AI, 32 animals were randomly assigned to a control, intravaginal progesterone for 14 days progesterone releasing intravaginal device (PRID) or GnRH treatment group. On days 5, 7, 12, 14, 17 and 19 post-AI, each animal underwent colour Doppler ultrasonography of the corpus luteum and blood samples were collected for cell counts and plasma progesterone determination. Through general linear model repeated measures analysis of variance, significant effects were observed of treatment, parity, inseminating bull, reduced vascularization of the CL and pregnancy on plasma progesterone concentrations, whereas mean plasma progesterone and time luteal phase day, and treatment and plasma progesterone concentration on day 5 post-AI were found to, respectively, affect neutrophil and lymphocyte counts throughout the luteal phase. Moreover, two binary logistic regression analyses were performed. Based on the odds ratio, the likelihood of pregnancy by days 26-32 post-AI was 23.4 times higher in animals with high mean progesterone levels throughout the study period, compared with animals with low mean progesterone. The likelihood of reduced CL vascularization was 14 times higher in animals treated with PRID, compared with control and GnRH-treated animals. In conclusion, our results indicate that treatment on day 5 post-AI with PRID reduced subsequent CL vascularization, whereas GnRH treatment increased plasma progesterone concentrations on day 12 post-AI, although an effect was identified of the inseminating bull on plasma progesterone levels. Pregnant animals showed higher mean plasma progesterone concentrations than in nonpregnant ones and heifers higher than in lactating cows, whereas blood cell counts differed depending on the treatment and on the mean plasma progesterone concentration on day 5 post-AI.     

Changes of Connexin43 Expression in Non‐pregnant Porcine Myometrium Correlate with Progesterone Concentration During Oestrous Cycle

Connexin43 (Cx43) is a major protein of myometrial gap junctions. The number of Cx43 gap junctions increase dramatically with the onset of labour in association with development of synchronized uterine contractions. The formation of myometrial gap junctions follows an increase in the oestrogen to progesterone ratio indicating an important role of steroid hormones in regulating Cx43 expression at term. However, no relationship has been established between the expression of Cx43 in the non‐pregnant myometrium and concentration of steroid hormones during the oestrous cycle. Here, we used immunofluorescence and Western blotting to analyse the expression of Cx43 gap junctions in the myometrium of pre‐pubertal pigs (n = 7) and mature pigs at pre‐ovulatory (n = 7), luteal (n = 5) and late luteal (n = 3) stages of the oestrous cycle. The number of Cx43 gap junctions calculated per 1 mm² of the myometrial section was low in pre‐pubertal pigs and significantly higher (p < 0.022) in pre‐ovulatory animals. In relation to pre‐ovulatory animals the number of myometrial gap junctions was significantly lower (p < 0.019) at the luteal phase and correlated with significantly higher (p < 0.005) concentration of endogenous progesterone. Phosphorylated isoforms of Cx43 protein were expressed in the myometrium of pre‐pubertal pigs and mature animals at pre‐ovulatory and late luteal phases, while they were down regulated at the luteal stage. These results indicate that changes of Cx43 expression in the porcine myometrium during the oestrous cycle may be regulated by progesterone concentration and may contribute to the modulation of uterine motility.     

The connections of lymphatic vessels draining female reproductive organs with lymphnodes in the pig

The connections of lymphatic vessels leaving the reproductive organs (ovary, oviduct, uterine horn, corpus and cervix, and vagina) with lymphnodes (normal and hemal) located in the uterine broad ligament and paraaortal regions were examined in the cyclic and immature pigs. To visualize the lymph pathways, the lymphatic lumen was filling with varicoloured microfil and/or ink-gelatin mass introduced all the way down to appearance in several nodes. This study revealed that lymphatics emanating from the uterine horn, corpus and the anterior part of the cervix demarcated large a lymphatic area in the porcine broad ligament. From the caudal portion of the cervix and vagina 2-3 lymphatics were found to emerge running near walls of these organs and connecting with large complex nodes, and 2-3 lymphatics reaching the plica urogenitalis. Generally, the lymphatic vessels leaving the porcine reproductive organs were connected by collector lymphangions with 3-5 normal-, 0-3 hemal- and one large composed nodes all found between the distal vascular subovarian plexus and the uterine artery as well as with 9-27 normal and 3-9 hemal nodes in the paraaortal region.     

A survey of the postpartum reproductive performance of dairy cows with fertility problems in southern Iceland

The purpose of this survey was to evaluate the reproductive performance of dairy cows on problem farms in southern Iceland. In all 229 cows on 6 farms were studied. The animals were examined clinically by rectal palpation, once a month. Blood samples were taken 2–5 and 7–10 weeks after calving. The blood samples were analysed for the contents of glucose, urea, inorganic phosphate, calcium and magnesium. Milk samples for progesterone profiles were taken, by the farmer, every 4th day from day 10 postpartum until first oestrus. Because of this sampling method, 128 cows had no rise in progesterone levels, when milk sampling was stopped. These 128 animals were excluded from the study. The results are based on 101 animals.There was a large variation between cows in postpartum reproductive performance. In the total material 1st ovulation occurred later than reported in many other countries. Fifty percent of the cows had ovulated 35 days after calving and 90 percent 70 days after calving.The first luteal phase was short in about 60 % of the cows. The progesterone values assayed from those short cycles were lower than the values assayed from the following cycle. First artificial insemination (ai) was on the average 77 days postpartum (pp). The conception rate to first service was 49 %. Of 100 milk samples taken at the time of ai, 20 had high progesterone value. This indicates a high frequency of luteal phase inseminations.Clinical ketosis was diagnosed in 35 cows. Of these, 31 had a low glucose value. Cows with clinical ketosis ovulated, on the average, later than other animals and 24 ovulated later than 40 days pp. The results indicated that the fertility problems of these cows studied were late ovulations, low conception rate, probably in part, due to luteal phase inseminations, and a high frequency of ketosis which could be caused by low quality feedstuff.     

Anatomicohistological Characteristics of the Female Genital Organs of the White‐lipped Peccary (Tayassu pecari) in the Peruvian Amazon

This study examined the anatomical and histological characteristics of the genital organs of the female white‐lipped peccary in the wild in different reproductive stages, collected by rural hunters in the North‐eastern Peruvian Amazon. Mean ovulation rate was 2.12 ± 0.83 follicles and litter size was 1.78 ± 0.41 embryos or fetuses per pregnant female, resulting in a low rate of reproductive wastage, averaging 0.33 ± 0.66 (16.04%) oocytes or embryos per pregnancy. The ovulation rate and the anatomical performance of the uterus could limit the prolificacy of this species. Females in follicular phase showed follicular waves suggesting the synchronous growth of a cohort of follicles. Different uterine and vaginal epithelium features changed in accordance with the reproductive state of the female. Pregnant females and females in the luteal phase presented a significant proliferation of endometrial uterine glands, characterized by hyperplasia and branching of endometrial glands, and increase in the proportion of cervical epithelial cells with periodic acid‐schiff (PAS)‐positive granules compared with that in females in the follicular phase. Females in the follicular phase showed a more developed vaginal epithelium (in thickness and in layer composition) than females in the luteal phase and pregnant females.     

Effects of time of progesterone supplementation on embryo development and interferon-tau production in the cow

We have investigated the effects of the timing of progesterone supplementation on early embryo development in mature, non-lactating Holstein-Friesian cows. Animals were inseminated 72 h (day 1) and 96 h following prostaglandin injection and were either left as untreated controls (n=6) or received progesterone supplementation from either days 5 to 9 (early; n=6) or from days 12 to 16 (late; n=6). Daily plasma samples were collected until day 16, when cows were slaughtered and reproductive tracts recovered and flushed to collect embryos and to measure interferon-tau activity. Both early and later progesterone supplementation resulted in marked increases in plasma progesterone (P<0.01). Early, but not late, progesterone supplementation resulted in a fourfold increase in trophoblast length (P<0.01) and a sixfold increase in uterine concentration of interferon-tau (P<0.05). The results demonstrate that progesterone supplementation during the postovulatory rise, but not later in the luteal phase, increases embryo development and interferon-tau production.     

Influence of estradiol on duration of anestrus and incidence of short estrous cycles in postpartum cows

The influence of exposure to exogenous estradiol on the interval from parturition to first ovulation, luteinizing hormone (LH) secretion and luteal function was examined in cows. Cows were assigned at parturition to one of three treatments. Cows received either a 3.0 (1-E; n = 30) or .75 cm (1/4-E; n = 28) implant containing 17 beta-estradiol or served as untreated control animals (C; n = 33). Implants were administered within 2 days following parturition and removed on day 40 postpartum (day 0 = day of parturition). Single blood samples were collected twice weekly and analyzed for progesterone to determine length of postpartum anestrus and duration of the initial increase in progesterone. Sequential blood samples were collected on day 35 +/- .1 postpartum (15 min intervals for 18 hrs) from 5 cows in each treatment and analyzed for LH. Concentrations of estradiol were higher (P less than .01) in the 1-E (5.3 +/- .24) than in C (3.9 +/- .23) or 1/4 E (3.9 +/- .25) cows on day 35 postpartum. The interval from parturition to the first estrous cycle of normal duration was similar for cows in the C and 1-E treatment (53 +/- 2.4 and 56 +/- 2.4 days, respectively). Cows in the 1/4-E treatment had a longer (P less than .05) interval (68 +/- 2.5 days). Secretion of LH was similar among treatments on day 35 postpartum. The first normal luteal phase after parturition was preceded by a transient rise in progesterone in 81, 64 and 85% of the cows in the C, 1-E and 1/4-E treatments, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)