Sources of variation in response intervals after prostaglandin treatment in mares with functional corpora lutea.

Sixty-two non-cycling mares were classified according to the size of largest follicles at the time of treatment with Prostalene, an analogue of prostaglandin (PG) F-2 alpha. Although oestrus occurred in only 77.4% of mares, 98.4% ovulated at an average of 6.8 days after treatment. Greatest variance of interval to ovulation was observed in mares having follicles greater than or equal to 40 mm at the time of treatment. This was due to regression of large follicles about one-third of the time and later ovulation of a succeeding follicle. This resulted also in greatest uncertainty of prediction of ovulation time based on ovarian palpation. Ninety foaling mares were given Prostalene at various days following the first ovulation post partum. Ovulation less than 6 days after treatment was strongly associated with the presence of a large follicle on the day of treatment. Otherwise most (72%) ovulations occurred 6--10 days after treatment. The distribution of interovulatory periods resulting from Prostalene on Day 6 after ovulation differed from that of Day 8 treatment.     

The effect of postpartum uterine lavage on foal heat pregnancy rate

Mares (n = 37) were treated on Days 2 and 4 post partum with a uterine lavage of 10 l of warm, sterile NaCl (0.9%) solution. Endometrial cytology and culture were performed on Day 7. Mares were bred on the first postpartum estrus by artificial insemination. Pregnancy rates were determined by ultrasound examination at Day 16 post ovulation. No differences were noted in degree of uterine inflammation or presence of uterine bacteria at Day 7 post partum between treated (n = 18) and control (n = 19) mares. Pregnancy rates at the first postpartum estrus for treated mares (55.5%) was not statistically different from that of control mares (68.4%). No advantage was noted in the use of intrauterine lavage with 10 l of warm sterile NaCl (0.9%) at Days 2 and 4 post partum as a means of improving foal heat pregnancy rate.     

Biodegradable estradiol microspheres do not affect uterine involution or characteristics of postpartum estrus in mares

Quarterhorse mares were used to investigate effects of estradiol-17beta on uterine involution, duration of estrus, interval to ovulation, and fertility achieved by breeding on the first postpartum estrus. On the day of foaling, mares were injected with biodegradable poly (DL-lactide) microspheres containing either 100 mg estradiol-17beta (25 mares) or no drug (27 mares). The treatment period was considered to last for 12 to 15 d. Estrus was determined by teasing mares (n=16) with a stallion. Ovulation was detected by transrectal ultrasonographic examination of ovaries (n=48). On Days 6, 11 and 16 post partum, transrectal ultrasonography was used to measure cross-sectional diameters of the uterine body, uterine horns, and fluid within the uterine lumen (n=28). Uteri were swabbed for bacteriologic culture, and uterine biopsies were obtained from the previously gravid uterine horn on Days 11 and 16 post partum, for assessment of endometritis and morphometric analysis of endometrial histioarchitecture (n=19). Twenty-two mares were bred on foal-heat, and pregnancy was determined by transrectal ultrasonography on 14 to 16 and 30 to 35 d after breeding. With only one exception (diameter of previously gravid uterine horn on Day 11), mean values for all measures of uterine involution did not differ between treatment groups (P > 0.05). No differences were detected between treatment group means for length of estrus or interval to ovulation (P > 0.05). No differences were detected between treatment group liklihoods for recovery of potential bacterial pathogens, presence of endometritis, or presence of intrauterine fluid at 11 or 16 d post partum (P > 0.05). Pregnancy rate of mares treated with estradiol (5 11 ; 45%) was not different from that of control mares (9 11 ; 82%; P > 0.05). Estradiol treatment did not hasten uterine involution, increase duration of estrus, delay ovulation, or increase fertility in these postpartum mares.     

Effects of postparturient uterine lavage on uterine involution in the mare

Eighteen postparturient mares were used to evaluate effects of uterine lavage on uterine involution. Mares were randomly assigned to one of three treatment groups: Group 1 (seven mares), no lavage; Group 2 (five mares), lavage on Day 3 post partum; and Group 3 (six mares), lavage on Days 3, 4, and 5 post partum. Five liters sterile physiologic saline, prewarmed to 42 degrees C, were used for each lavage. Transrectal ultrasound examination of the reproductive tract was performed on Day 11 post partum to detect the presence of free fluid in the uterine lumen, to estimate the cross-sectional diameter of the uterine horns and body, and to determine if ovulation had occurred. Endometrial biopsies were also taken on Day 11 post partum to evaluate endometrial histologic characteristics. Lavage had no effect (P>0.05) on diameter of the uterine body or previously gravid uterine horn, presence of fluid in the uterine lumen, or number of mares which had ovulated by Day 11 post partum. Histologic characteristics of the endometrium (height of luminal epithelium, gland depth, relative gland vclume, and inflammatory-cell score) were not affected by treatment (P>0.05). Postpartum uterine lavage did not significantly affect uterine involution by the parameters measured in normal-foaling mares at Day 11 post partum.     

Periparturient events in ovariectomized embryo transfer recipient mares

Ovariectomized mares treated with progesterone have established and maintained pregnancy after embryo transfer. This study evaluated the ability of ovariectomized embryo transfer recipients to successfully undergo parturition, raise a foal, and return to a useful reproductive status. Periparturient events in three ovariectomized embryo transfer recipient mares and three intact mares were compared. All mares foaled normally. Mammary scores were similar for both groups and all mares produced sufficient colostrum and milk to allow normal growth of healthy foals. Plasma progesterone levels decreased to < 5 ng/ml by Day 4 post partum in both groups. Progesterone concentrations continued to decrease and remained at <1 ng/ml in ovariectomized mares, but increased after the first postpartum ovulation (Day 9 to 15) in intact mares. Endometrial involution as determined by histological evaluation was complete in ovariectomized mares by Day 10 post partum and in intact mares by Day 11 post partum. As assessed by palpation per rectum and clearance of bacteria from the uterus, uterine involution was similar in all mares. The three ovariectomized mares subsequently received embryos by transcervical transfer and two of them established pregnancy. These results indicate that normal parturition, lactation, maternal behavior and uterine involution are independent of ovarian function.     

Persistence of the luteal phase following ovulation during altrenogest treatment in mares

Two experiments were conducted to test the efficacy of altrenogest treatment in mares. The response to 15-d altrenogest treatment (Experiment 1) was characterized in 20 mares that were given 22 mg daily of altrenogest in oil (n = 10) or in gel (n = 10) from Day 10 to 25 after ovulation. In 17 mares, luteolysis occurred during altrenogest treatment (Day 17.7 +/- 0.5), while 2 mares retained their corpus luteum (CL), and 1 mare had a diestrous ovulation on Day 16, resulting in a prolonged luteal phase. Ten of the 17 mares in which the CL had spontaneously regressed returned to estrus after the end of treatment, and ovulated 5.7 +/- 0.8 d after the end of altrenogest treatment. Two of these 17 mares ovulated 2 and 3 d after the end of altrenogest treatment but ovulation was not accompanied by estrous behavior, and 5 mares ovulated during altrenogest treatment resulting in an interovulatory interval of 22.4 +/- 1.1 d (range: 20 to 25d). Five mares which ovulated during altrenogest treatment and 2 mares which ovulated during silent estrus after the end of altrenogest treatment failed to regress the CL around 14 d post ovulation, and had a prolonged luteal phase. In Experiment 2, the effect of altrenogest administered from luteolysis to ovulation on duration of the subsequent luteal period was analyzed. In 6 mares altrenogest was begun on Day 14 post ovulation and continued until the hCG-induced ovulation. The interval from ovulation during altrenogest treatment to spontaneous luteolysis was 45.6 +/- 2.4 d (range: 40 to 54d) in altrenogest-treated mares and was significantly longer than in 10 untreated control mares (14.5 +/- 0.3 d, range: 13 to 16d). The results suggest that the oil and gel altrenogest preparations are equally effective in modulating estrous behavior and time to estrus and ovulation. Altrenogest treatment started late in diestrus appears to result in a high incidence of ovulation during treatment and when luteolysis and ovulation occur during treatment; the subsequent luteal phase is frequently prolonged due to failure of regression of the CL.     

Two-dimensional polyacrylamide gel electrophoresis of proteins synthesized and released by conceptuses and endometria from pony mares

Conceptuses were obtained from pony mares on each day of pregnancy between Days 12 and 28, and on Days 39, 45, 65 and 100. Endometrium was obtained from mares at Days 12, 14, 16, 18, 39, 45, 65 and 100 of pregnancy, and from non-pregnant mares during anoestrus, during transition into the breeding season, at oestrus, or during dioestrus. Tissues were incubated in vitro for 24 h with L-[3H]leucine. Proteins synthesized and released into the culture medium were analysed by two-dimensional polyacrylamide gel electrophoresis (2-D PAGE) and fluorography. Conceptuses obtained before Day 14 after ovulation released a characteristic pattern of labelled proteins. These included two groups of apparent isoelectric variants of relative molecular weights (Mr) 30,000-40,000 (pI values 4.5-5.5 and 6-7), one group of Mr approximately 22,000 (pI 6.5-7), and large protein(s) that did not enter the 10% polyacrylamide gel. After Day 14 the array of labelled proteins had changed and resembled that produced by isolated yolk sac at the later stages of pregnancy studied. Included amongst these were several acidic polypeptides with Mr 20,000 (pI 5-6). The endometrial samples released an array of non-dialysable polypeptides into the culture medium. Fluorograms could be assigned to one of three general groups, with endometrium from mares within each group producing similar patterns of labelled proteins. The first group consisted of anoestrous, transitional and ovariectomized mares, and mares at oestrus or Day 1 or Day 18 after ovulation. The second group was comprised of mares at Days 12-16 of dioestrus or Days 12-18 of pregnancy.(ABSTRACT TRUNCATED AT 250 WORDS)     

The effect of intrauterine and cervical manipulation on the equine oestrous cycle and hormone profiles.

Endometrial biopsy or endometrial biopsy and uterine culture taken on Day 4 after oestrus induced lysis of the corpus luteum (CL), resulting in a sharp decline in serum progesterone concentration and shortened the interoestrous interval in 8/12 and 32/33 oestrous cycles, respectively, during 2 experiments. Cervical dilatation 4 days after oestrus shortened the interoestrus interval in 5/10 and 0/5 oestrous cycles. Endometrial biopsy and culture on Days 1 and 3 after oestrus also induced CL lysis during 4 of 7 cycles. Total oestrogen (oestrone plus oestradiol) concentrations increased at the onset of the subsequent oestrus in mares biopsied on Day 4 of dioestrus or in control cycle oestrous periods. Endometrial biopsy also induced lysis of the CL in mares with persistent luteal function. It is postulated that intracervical or intrauterine manipulations during the luteal phase of the oestrous cycle may directly, or indirectly, stimulate the release of an endogenous luteolysin (prostaglandin) resulting in CL regression, followed by oestrus and ovulation in the mare.     

Effects of reducing the remating interval after parturition on the fertility and plasma concentrations of luteinizing hormone, prolactin, oestradiol-17 beta and progesterone in lactating domestic rabbits

Primiparous crossbred does were remated on Day 1 (n = 15) or 14 (n = 25) post partum and killed on Day 10 post coitum to assess their fertility. Blood samples were taken during the pre- (0-12 h post coitum) and post- (1-10 days post coitum) ovulatory periods and plasma was assayed for luteinizing hormone (LH), prolactin, oestradiol-17 beta and progesterone. Ovulation response was significantly greater (P less than 0.01) and ovulation rate significantly lower (P less than 0.001) in does mated on Day 1 than in those mated on Day 14 post partum. Does failing to ovulate on Day 14 post partum exhibited no preovulatory LH surge and had significantly lower (P less than 0.05) premating concentrations of oestradiol-17 beta and prolactin than those ovulating at this time. No significant differences in hormone concentrations were observed during the preovulatory period between does ovulating on Days 1 and 14 post partum, with the exception of oestradiol-17 beta. Concentrations of this hormone were significantly lower (P less than 0.01) in does mated on Day 1, at 1 h post coitum. We conclude that (i) fertility was affected by the remating interval after parturition, (ii) ovulation failure was associated with an absence of the preovulatory LH surge and a reduction in premating concentrations of oestradiol-17 beta and prolactin and (iii) the lower ovulation rate in early lactation was apparently caused by a reduction in ovarian competence to respond to the gonadotrophic stimulus.     

Initiation of superovulation in mares 5 or 12 days after ovulation using equine pituitary extract with or without GnRH analogue

Cyclic mares were assigned to 1 of 3 treatments (n=15 per group): Group 1 received equine pituitary extract (EPE; 25 mg, i.m.) on Day 5 after ovulation; Group 2 received EPE on Day 12 after ovulation; while Group 3 received 3.3 mg of GnRH analogue (buserelin implant) on the day of ovulation and 25 mg, i.m. EPE on Day 12. Mares in each group were given 10 mg PGF(2)alpha on the first and second day of EPE treatment. The EPE treatment was continued daily until the first spontaneous ovulation, at which time 3,300 IU of human chorionic gonadotropin (hCG) were given to induce further ovulations. Mares in estrus with a >/=35 mm follicle were inseminated every other day with pooled semen from 2 stallions. Embryo recovery was attempted 7 days after the last ovulation. Follicular changes and embryo recovery during 15 estrous cycles prior to treatment were used as control data. During treatment, the number of follicles >/=25 mm was higher (P<0.05) for Day 5 than for Day 12 or control mares, but the number for Day-5 mares was similar (P>0.05) to that of mares treated with buserelin implants (Group 3). Initiation of EPE treatment on Day 5 resulted in a greater (P<0.05) number of ovulation (2.9) than on Day 12 (1.1) or in the control mares (1.3) but not in the buserelin-treated mares (1.8). The number of embryos recovered from mares in the Day 5 (1.2), Day 12 (1.0), buserelin (0.9) and control (0.9) groups was similar (P>0.05). The conclusions were 1) EPE initiated in early diestrus increased follicular development and ovulation and 2) treatment with GnRH analogue marginally improved response to EPE treatment.     

Fertility, ovulation and maturation of eggs in mares injected with HCG

Pony mares were observed from January to August for incidence of oestrus, duration of oestrus, length of the oestrous cycle and for ovulation and fertility after injection of HCG. From January to 15 May most mares showed oestrus but the duration of oestrus was quite variable and few mares ovulated in response to HCG. From 15 May to 17 August oestrous cycles were more regular and ovulation was induced within 40-50 h by an intramuscular injection of 1500-5000 i.u. HCG. Pregnancy was established by one mating at a fixed time after HCG in 20 of 69 mares. Degenerate eggs were recovered from the oviducts of anoestrous recently ovulated, mated, unmated and pregnant mares. The first polar body was formed before ovulation in 2 eggs and had not formed in 2 recently ovulated eggs flushed from the oviduct. The second polar body formed after sperm penetration 10-12 h after ovulation. After formation of pronuclei, the first cleavage division occurred at 20 h and the second at 32 h after ovulation. Oestrus was inhibited by progesterone administered by vaginal devices but occurred within 1-3 days in 12 of the 20 mares after withdrawal of the devices.     

Deslorelin on Day 8 or 12 postovulation does not luteinize follicles during an artificially maintained diestrous phase in the mare

Practical estrus synchronization schemes are needed for mares. The Ovsynch synchronization protocol for cattle involves the administration of gonadotropin-releasing hormone (GnRH) to induce ovulation or luteinization of dominant follicles during the luteal phase and prostaglandin 7 days later to cause regression of any luteal tissue and development of a preovulatory follicle. An Ovsynch-type synchronization program potentially could be developed for horses if luteinization or ovulation of diestrous follicles occurred in response to GnRH treatment. The objective of this study was to determine if administration of the GnRH agonist, deslorelin acetate, on Day 8 or 12 postovulation would induce luteinization or ovulation of diestrous follicles in the mare. The model used was cycling mares maintained in an artificial luteal phase by administration of a synthetic progestin following prostaglandin-induced luteal regression. On the day of ovulation, 21 light horse mares were randomly assigned to one of three groups: (1) no GnRH, altrenogest from Days 5 to 15 postovulation with prostaglandin on Day 15; (2) GnRH on Day 8, altrenogest from Days 5 to 15 with prostaglandin given on Day 6 to induce luteolysis of the primary corpus luteum, an implant containing 2.1mg of deslorelin acetate inserted on Day 8 and removed on Day 10, with a second prostaglandin treatment on Day 15; (3) GnRH on Day 12, altrenogest from Days 9 to 19, prostaglandin on Day 10, a deslorelin acetate implant injected on Day 12 (subsequently removed on Day 14), and a second dose of prostaglandin administered on Day 19. Follicular development was monitored every other day from Day 5 until a 30-mm sized follicle was observed, and then daily to detection of ovulation. Serum progesterone concentrations were determined daily for 12 consecutive days. Progesterone concentrations in Group 1 remained elevated until approximately Day 12 postovulation. Prostaglandin administration on Day 15 resulted in complete luteolysis in all seven mares. In Group 2, progesterone concentrations in six of seven mares declined to baseline after prostaglandin treatment. No increase in serum progesterone was noted in any of the six mares that were given GnRH on Day 8, including three mares that had diestrous follicles > or =30mm in diameter at the time of treatment. Similarly, progesterone concentrations in six of seven mares in Group 3 declined to baseline after prostaglandin and there was no increase in progesterone after administration of GnRH on Day 12. No ultrasound evidence of luteinization or ovulation of diestrous follicles were noted after GnRH administration in any mares of Group 2 or 3. In conclusion, administration of the GnRH agonist deslorelin acetate to mares failed to induce luteinization or ovulation of diestrous follicles. Consequently, the Ovsynch program (as used in cattle) has little efficacy for synchronization of estrus in mares.     

Fertility of prostaglandin-induced oestrus compared to normal post-partum oestrus.

This study was undertaken to determine if fertility could be improved by increasing the interval from foaling to breeding. Forty-two mares, not bred during normal post-partum oestrus, were injected with a prostaglandin analogue on Day 6 or 7 following ovulation. Mares were mated artifically with antibiotic-treated semen during the resulting oestrus and, if necessary, for the following 4 cycles. Their fertility was compared, by cycles/pregnancy and rate of fetal loss, to mares bred by the same methods on 86 normal post-partum oestrous periods. The interval from foaling to the onset of breeding and the duration of oestrus were longer in the injected mares than the intervals observed in the untreated mares. Both groups averaged 1.3 breeding periods/pregnancy. The rate of fetal loss was not significantly different between the groups. Increasing the interval from foaling to breeding did not improve fertility.     

Fertility of donor mares following nonsurgical collection of embryos.

Embryos were collected nonsurgically on Day 7 or 8 after ovulation from 7 Quarter horse mares using a modified 30-ml Foley catheter to flush the uterine horn ipsilateral to the recent ovulation with 500 ml TCM-199 containing Hepes buffer. After collection, the uteri were infused with nitrofurazone to reduce the chances of infection due to the procedure. Eleven collections from 7 mares resulted in recovery of 9 embryos and nonsurgical transfer of 4 of these resulted in the birth of one foal. After collections, 8 oestrous cycles averages 22.75 days and 2 extended oestrous cycles were 43 and 59 days long respectively. Of 6 mares mated after one or two embryo collections, 5 conceived to a single service and the sixth during the third oestrus in which she was covered.     

Synchronization of oestus and timed insemination of mares.

Oestrus was synchronized in 116 mares by means of an i.m. injection of prostaglandin F-2 alpha (Day 0) and of fluprostenol (a PG analogue) on Day 16. Mares were then randomly divided into three groups. Group A mares (N = 30) were given 2500 i.u. hCG I.M. ON Day 20 and artificially inseminated on Day 21 without detection of oestrus. Group B mares (N = 32) were given 2500 i.u. hCG i.m. on Day 20 and inseminated on Days 21 and 23, also without oestrus detection. Group C mares (N = 54) were teased on Days 18, 19, 21, 23 and 25 and inseminated on Days 19, 21, 23 and 25 while they were in oestrus. Semen was collected by artificial vagina from 3 stallions. One-third of the mares in each group were assigned to each stallion at random. The gel-free fraction was divided equally among the mares, and used within 1 h of collection. Pregnancy rates at about 60 days of gestation were not significantly different. A high rate of synchronization of oestrus (80%) was attained within 48 h of treatment with fluprostenol.     

Alterations in hypophysial responsiveness to synthetic GnRH at different postpartum intervals in Murrah buffalo (Bubalus bubalis )

The objective of this study was to investigate the hypophysial responsiveness to GnRH at different intervals post partum in Murrah buffalo. Plasma LH and FSH levels were measured at 1 h before and upto 6 h subsequent to the administration of GnRH (1 ug/kg body weight) or saline on Days 2, 20 and 35 post partum in 2 groups of buffalo (n=4 each). Plasma progesterone levels were measured in samples collected once daily from Day 3 to Day 46 post partum. Pretreatment basal LH levels exhibited a progressive increase from Day 2 through Day 35 post partum, while the basal FSH levels increased only until Day 20 post partum. Following a highly subdued LH response to GnRH on Day 2 post partum, a 408% increase (P < 0.01) was observed in the total LH released in response to GnRH on Day 20 post partum, followed by a 20% reduction (non-significant) over Days 20 to 35 post partum. The interval from parturition was highly correlated with total LH released (r = 0.711, P < 0.01). Unlike LH, a substantial amount of FSH was released following GnRH treatment on Day 2 post partum, which was not significantly different from the FSH response on Days 20 and 35 post partum. The LH and FSH response to GnRH was not significantly different between animals in which luteal activity resumed and in those which showed no luteal activity post partum. While pointing to a dramatic enhancement in the hypophysial responsiveness to GnRH between Days 2 and 20 post partum, these results suggest that pituitary responsiveness to GnRH does not appear to be the limiting factor for resumption of estrous cycles by Day 35 post partum in Murrah buffalo.     

Gene profiling of inflammatory genes in day 18 endometria from pregnant and non‐pregnant mares

Maternal recognition of pregnancy is a physiological process that primarily describes endometrial responses to a conceptus. Recognition of a conceptus prevents the release of prostaglandin F_2α, thereby ensuring survival of the corpus luteum and continued progesterone production. Exactly how this occurs in the mare is poorly understood. Because prostaglandin F_2α is a pro‐inflammatory hormone, we hypothesized that differential gene expression in the endometrium at the time of maternal recognition reflects an anti‐inflammatory event leading to decreased prostaglandin F_2α secretion. Mares were inseminated, and endometrial biopsies were recovered from pregnant mares on Day 18 post‐ovulation. In subsequent estrous cycles, mares were not inseminated and Day 18 post‐ovulation endometrial biopsies were collected (non‐pregnant control, matched per individual). Endometrial gene expression profiles were examined by screening an Affymetrix equine GeneChip containing probes specific for genes related to inflammatory processes. Microarray analysis revealed 118 genes that were up‐regulated and 93 genes that were down‐regulated (P < 0.001) at least 1.5‐fold in the endometrium of pregnant versus non‐pregnant mares. Quantitative, real‐time RT‐PCR confirmed the microarray results for three up‐regulated genes homologous to TSC22D3, PPAPDC2, and KLF6, and three down‐regulated genes homologous to ESR1, MARCKSL1, and EPSTI1 (P < 0.05). It is concluded that the presence of the equine embryo induces differential gene expression in the endometrium of Day 18 pregnant mares, and that these genes are associated with inflammatory processes and pathways involving cellular growth and proliferation. The results from this study provide important new insights into endometrial gene expression in response to early equine pregnancy. Mol. Reprod. Dev. 79: 777–784, 2012. © 2012 Wiley Periodicals, Inc.     

Embryo loss following GnRH-induced ovulation in anovulatory mares

Two experiments were conducted using a 21-day GnRH analogue treatment regimen to induce ovulation in seasonally anovulatory mares. In Experiment 1, nontreated (n=20) and treated (n=83) mares were defined as having inactive ovaries (largest follicle相似文献   

Changes in vascular perfusion of the endometrium in association with changes in location of the embryonic vesicle in mares

The equine embryonic vesicle is mobile on Days 12-14 (Day 0 = ovulation), when it is approximately 9-15 mm in diameter. Movement from one uterine horn to another occurs, on average, approximately 0.5 times per hour. Mobility ceases (fixation) on Days 15-17. Transrectal color Doppler ultrasonography was used to study the relationship of embryo mobility (experiment 1) and fixation (experiment 2) to endometrial vascular perfusion. In experiment 1, mares were bred and examined daily from Day 1 to Day 16 and were assigned, retrospectively, to a group in which an embryo was detected (pregnant mares; n = 16) or not detected (n = 8) by Day 12. Endometrial vascularity (scored 1-4, for none to maximal, respectively) did not differ on Days 1-8 between groups or between the sides with and without the corpus luteum. Endometrial vascularity scores were higher (P < 0.05) on Days 12-16 in both horns of pregnant mares compared to mares with no embryo. In pregnant mares, the scores increased (P < 0.05) between Day 10 and Day 12 in the horn with the embryo and were higher (P < 0.05) than scores in the opposite horn on Days 12-15. In experiment 2, 14 pregnant mares were examined from Day 13 to 6 days after fixation. Endometrial vascularity scores and number of colored pixels per cross-section of endometrium were greater (P < 0.05) in the endometrium surrounding the fixed vesicle than in the middle portion of the horn of fixation. Results supported the hypothesis that transient changes in endometrial vascular perfusion accompany the embryonic vesicle as the vesicle changes location during embryo mobility.     

Changes in equine endometrial oestrogen receptor alpha and progesterone receptor mRNAs during the oestrous cycle, early pregnancy and after treatment with exogenous steroids

Two experiments were performed to determine changes in the abundance of oestrogen and progesterone receptor (ER alpha and PR) mRNAs in equine endometrium during the oestrous cycle and early pregnancy, and under the influence of exogenous steroids. In Expt 1, endometrial biopsies were obtained from non-mated mares during oestrus and at days 5, 10 and 15 after ovulation, and from pregnant mares at days 10, 15 and 20 after ovulation. There were overall effects of day on the abundance of ER alpha (P = 0.0001) and PR (P = 0.0014) mRNAs. The amount of ER alpha mRNA decreased at day 10 of pregnancy, and PR mRNA was reduced at day 5 in non-mated mares and at day 15 of pregnancy, compared with oestrous values. Experiment 2 was conducted to determine the effects of exogenous steroids on endometrial ER alpha and PR mRNAs. Endometrial biopsies were obtained from 19 anoestrous mares that had been treated with vehicle, oestradiol, progesterone, or oestradiol followed by progesterone for either a short or a long duration. The steroid treatment affected the abundance of ER alpha mRNA (P = 0.0420), which was higher (P < 0.05) in the oestradiol group than in the group treated with oestradiol followed by long duration progesterone. The steroid treatment did not affect the abundance of PR mRNA. These results demonstrate that the amount of steroid receptor mRNA changes with the fluctuating steroid environment in the uterine endometrium of cyclic and early pregnant mares, and that the duration of progesterone dominance may affect ER alpha gene expression. In addition, factors other than steroids may regulate ER alpha and PR gene expression in equine uterine endometrium.