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.     

Ultrasonographic evaluation of uterine involution and postpartum follicular dynamics in French jennies (Equus asinus)

Uterine involution and follicular dynamics during postpartum period were studied ultrasonographically in French jennies. For the study of uterine involution in postpartum jennies (n = 6, Group S), sonographic measurements of different parts of the uterus and endometrium were made at three-day interval, starting from the day of foaling and continued up to 33 days postpartum. Uterine dimensions were also recorded in non-pregnant jennies (n = 3, Group C) throughout a cycle and compared with the dimensions of Group S jennies observed on the day of complete involution. Follicular dynamics of first and second postpartum ovulatory cycles were studied and compared with that of the single estrous cycle of Group C jennies. Jugular venous blood samples of Group S jennies were collected at weekly intervals for 49 days, commencing at the appearance of first preovulatory follicle, to support the sonographic findings. The average involution period was 22.5 +/- 1.7 days. However, it was significantly delayed (P < 0.05) in jennies which came into first postpartum ovulatory heat within Day 9 than those who came later (25.0 +/- 1.0 versus 20.0 +/- 1.0). The endometrial layer was not discernible beyond Day 15 postpartum and thus was found to be unreliable index of uterine involution. The follicular growth rate (mm per day) and diameter (mm) of preovulatory follicle in postpartum jennies were similar to that in normal cycling jennies (P > 0.05). The first and second ovulations occurred at 14.6 +/- 0.8 and 39.0 +/- 0.8 days postpartum in Group S jennies. All the corpora lutea, either echogenic or centrally non-echogenic were functionally similar and had similar life span (P > 0.05). In conclusion, the postpartum reproductive events related to uterine involution and ovarian cyclicity apparently resemble that of mares.     

The postpartum buffalo: I. Endocrinological changes and uterine involution

To maintain a calving interval of 13-14 months in buffaloes, successful breeding must take place within 85-115 days after calving. Disturbances during this period due to delay of uterine involution or resumption of estrous activity are likely to prolong the calving interval and reduce the lifetime reproductive and productive efficiency. In this article literature on endocrinological changes in the peripartum period and on factors affecting uterine involution are reviewed. The available information indicated that although the availability of releasable FSH does not appear to be a limiting factor for resumption of postpartum cyclicity a substantial increase of releasable LH and replenishment of pituitary stores occurred around Day 20 in dairy and Day 30 in swamp buffaloes. There is evidence that follicular activity is resumed early (15-30 days) in the postpartum period. However, the factors which initiate release of appropriate LH pulses, follicular maturation and ovulation in the postpartum buffalo need further studies. The mean interval to complete uterine involution varied widely between 19 and 52 days. Assessment of cervical and uterine horn diameters by rectal palpation alone is not satisfactory to diagnose delayed uterine involution and possible subclinical uterine infection. Vaginal inspection can be included as a fundamental part of postpartum genital examination for diagnosis of such case. Uterine involution, however, does not seem to be a limiting factor for achievement of satisfactory fertility in the postpartum buffalo but the main determinant is resumption of estrous activity.     

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 gonadotropin releasing hormone and prostaglandin F(2)alpha on the reproductive performance in postpartum cows

A study was conducted to determine whether treatment with gonadotropin releasing hormone (GnRH) in combination with prostaglandin F(2)alpha (PGF(2)alpha) could enhance ovarian activity and uterine involution in postpartum dairy cows to reduce the calving interval. Cows were randomly assigned to one of three treatment groups. Cows (n = 8) in Group 1 received 100 mug GnRH intramuscularly (i.m.) twice on Day 20 and Day 35 postpartum, and 25 mg PGF(2)alpha i.m. on Day 47 postpartum. Group 2 (n = 8) received a single i.m. injection of 100 mug GnRH on Day 25 postpartum and 25 mg PGF(2)alpha i.m. on Day 37 postpartum. The Control Group (n = 9) did not receive hormonal treatment. Palpation per rectum of the reproductive organs and serum progesterone (P) determination were performed twice a week to monitor ovarian activity and uterine involution. Postpartum interval to the first ovulation was short in treated groups (Group 1, 21.0 d; Group 2, 26.3 d) compared with Control Group (30.1 d, P < 0.05). Likewise, mean frequency of ovulation was increased in both treated groups compared with the Control Group (P < 0.05). Cows in treated groups required fewer days to complete uterine involution than in the Control Group. The mean interval to the first service, the conception rate at first service and the number of services per conception showed no significant differences among the three groups, but the mean days from calving to conception were shorter for the treated groups (78.7 d in Group 1; 83.3 d in Group 2) than (109.1 d, P < 0.05) for the Control Group. Our results suggest that combined treatment with GnRH and PGF(2)alpha may enhance ovarian activity in the postpartum cow, resulting in improved reproductive performance.     

The effect of intrauterine administration of estradiol on postpartum uterine involution in cattle

In cattle, the first postpartum dominant follicle has a predilection for the ovary contralateral to the previously gravid uterine horn. However, the presence of an estradiol-secreting dominant follicle in the ipsilateral ovary is a marker of subsequent fertility, possibly due to a localized effect of ovarian estradiol on uterine involution. The present study tested the hypothesis that estradiol increases the rate of uterine involution when administered into the previously gravid uterine horn around the expected time of selection of the first postpartum dominant follicle. Dairy cows were treated with 10 mg estradiol benzoate (n=15) or saline (n=14) administered through the cervix into the previously gravid uterine horn lumen on Days 7 and 10 postpartum. Uterine involution was monitored by daily transrectal ultrasonography and estimation of peripheral plasma concentrations of PGFM and acute phase proteins, while ovarian function was monitored by ultrasonography and measurement of plasma hormone concentrations. There was no effect of estradiol treatment on the diameter of the previously gravid or nongravid uterine horns, nor on the plasma concentrations of PGFM or acute phase proteins. However, cows in which the first postpartum dominant follicle ovulated during the study period had a smaller diameter of the previously gravid (P<0.01) or nongravid uterine horns (P<0.001) compared with cows in which the follicle regressed. Thus, our hypothesis was not proven, and the opposite pathway of utero-ovarian signaling may be more important during the postpartum period.     

Stimulation of 2',5'-oligoadenylate synthetase activity in sheep endometrium during pregnancy, by intrauterine infusion of ovine trophoblast protein-1, and by intramuscular administration of recombinant bovine interferon-alpha I1.

In Expt 1, activity of 2',5'-oligoadenylate (2',5'-A) synthetase in endometrium collected on Day 16 (oestrus is Day 0) from the uterine horn ipsilateral to the corpus luteum was greater (P less than 0.001) for pregnant (135.5 +/- 1.72 nmol/mg protein/h) than for cyclic ewes (58.5 +/- 0.99 nmol/mg protein/h). In pregnant ewes, activity of 2',5'-A synthetase in endometrium collected from the contralateral uterine horn (119.5 +/- 1.72 nmol/mg protein/h) did not differ from that of the ipsilateral horn. In Expt 2, three ovariectomized ewes were treated with progesterone for 10 days and then with oestrogen for 2 days. Activity of 2',5'-A synthetase on Day 13 was 18% greater (P less than 0.10) in endometrium collected from the uterine horn receiving infusions of 30 micrograms ovine trophoblast protein-1 (oTP-1) twice a day on Days 10, 11 and 12(57.7 +/- 0.22 nmol/mg protein/h) than from the uterine horn receiving control infusions of serum protein (SP; 48.8 +/- 0.22 nmol/mg protein/h). In Expt 3, activity of 2',5'-A synthetase on Day 15 was not significantly greater in endometrium collected from the uterine horn of cyclic ewes receiving infusions of 30 micrograms oTP-1 twice a day on Days 12, 13 and 14 (46.5 +/- 0.37 nmol/mg protein/h) than in endometrium from the uterine horn receiving infusions of SP (38.2 +/- 0.37 nmol/mg protein/h). When results of Expt 2 and Expt 3 were combined, intrauterine infusion of oTP-1 increased (P less than 0.05) activity of 2',5'-A synthetase in endometrium by 20%.(ABSTRACT TRUNCATED AT 250 WORDS)     

Bacteriological investigation of the postpartum uterus: Relationship to involution and histopathological findings

A bacteriological investigation of the postpartum uteri of suckled and nonsuckled Bunaji (White Fulani) cows was undertaken to determine the microflora, the effect of suckling on the flora and the influence of the flora on uterine involution and histopathology. Uterine contamination by bacteria was highest between days 10 and 21 postpartum with Staphylococcus aureus being the commonest organism isolated. There was no consistent isolation of one type of bacterial organism from a cow throughout the sampling period. Suckling did not affect the incidence of uterine contamination by bacteria. Foci of leucocytes (mainly lymphocytes) were found in uterine sections in an increasing frequency with days postpartum. Bacteria were isolated from only 3 of the 12 uteri that had the leucocytic foci. Uterine involution was normal and complete by 25 days after calving irrespective of the presence or absence of bacteria or leucocytic foci. We concluded that postpartum uterine contamination by bacteria was not influenced by suckling and that puerperal uterine contamination by bacteria did not interfere with the normal process and duration of uterine involution.     

Macrophage trafficking in the uterus and cervix precedes parturition in the mouse.

Immune activation is implicated in the etiology of preterm labor, but little is known about macrophage number or distribution in the uterus or cervix at term. This study tested the hypothesis that macrophages migrate into the reproductive tract before the onset of parturition. Paraffin-embedded sections from the mid-uterine horn and cervix of C3/HeN mice on Days 15 and 18 of pregnancy, the day of birth (Day 19), and 1 day postpartum were stained with a pan-macrophage marker to analyze cell numbers and distribution. During pregnancy, uterine macrophages were dispersed in endometrium, usually associated with vasculature and subluminal epithelium. In myometrium, macrophages were clustered in stromal connective tissue; near term and postpartum, cells appeared to surround the muscle bundles. Total macrophage numbers were increased on Day 15 relative to those in nonpregnant controls, declined before birth, and increased postpartum. In the cervix, macrophages congregated in subepithelium, often perivascular or near ganglia. Macrophage numbers in the cervix peaked on Day 18, then declined to nonpregnant levels by the day after birth. Thus, macrophage numbers in the uterus were inversely related to those in the cervix. These findings raise the possibility that macrophages and their products may be involved in uterine contractility and cervical remodeling during the processes of parturition.     

Effect of postpartum suppression of ovulation on uterine involution in dairy cows

The objective of this study was to investigate the effect of time of first postpartum ovulation after calving on uterine involution in dairy cows with and without uterine puerperal disease. Transvaginal follicular puncture (FP) of follicles >6 mm suppressed ovulation and development of a CL until Day 42 after calving. Fifty-three lactating Holstein Friesian cows (3.4 ± 1.2 years old, parity 2.5 ± 1.0 [median ± mean absolute deviation]) were divided into groups on the basis of the presence (UD+) or absence (UD−) of uterine disease and whether FP was carried out (FP+) or not (FP−). Uterine disease was defined as the occurrence of retained fetal membranes and/or metritis. This resulted in the following groups: UD−FP− (n = 15), UD−FP+ (n = 13), UD+FP− (n = 13), and UD+FP+ (n = 12). A general examination, vaginoscopy, transrectal palpation, and transrectal B-mode sonography of the reproductive organs were conducted on Days 8, 11, 18, and 25 and then every 10 days until Day 65 after calving. After hormonal synchronization of ovulation (cloprostenol between Days 55 and 60 postpartum and GnRH 2 days later), cows were inseminated in the next spontaneous estrus. On average, the cows ovulated on Day 21.0 ± 6.0 (UD−FP−), 50.0 ± 4.0 (UD−FP+), 16.0 ± 3.0 (UD+FP−), and 48.0 ± 2.0 (UD+FP+) postpartum. Calving-to-conception interval and first-service conception rates were not affected by FP (P > 0.05). Healthy cows with FP had smaller (P < 0.05) uterine horn and cervical diameters assessed sonographically than cows without FP. FP reduced the prevalence of purulent vaginal discharge and uterine size assessed transrectally in UD+ cows (P < 0.05). The results showed that suppression of an early ovulation by transvaginal FP improved uterine involution in cows with and without uterine disease.     

Prolapse of the nongravid horn in a cow with a seven-month pregnancy: A case report

Prolapse of the right nongravid horn of the uterus in a cow with a 7 1 2 - mo pregnancy is reported. The condition occurred 4 d after a vagino-cervical prolapse was reduced and fixed by Minchev's technique. The everted uterine horn together with its corresponding ovary became gangrenous and detached due to eschemic necrosis resulting from the constriction of the partially closed cervix. The cow delivered a healthy bull calf without any complications 6 wk after the incidence. Rectal examination of the cow 3 mo later showed completion of involution, uterus unicornis with its left ovary and a mature corpus luteum. The absence of the right ovary and the right uterine horn did not seem to interfere with the normal estrous cycle.     

Postpartum uterine infection in cattle

Postpartum uterine infections results from uterine contamination with bacteria during parturition. The prevalence of uterine infections varies considerably among studies. Uterine infection implies adherence of pathogenic organisms to the mucosa, colonization or penetration of the epithelium, and/or release of bacterial toxins that lead to establishment of uterine disease. The development of uterine disease depends on the immune response of the cow, as well as the species and number (load or challenge) of bacteria. The postpartum uterus has a disrupted surface epithelium in contact with fluid and tissue debris that can support bacterial growth. A variety of species of bacteria, both Gram-positive and Gram-negative aerobes and anaerobes, can be isolated from the early postpartum uterus. Most of these are environmental contaminants that are gradually eliminated during the first 6 weeks postpartum. A normal postpartum cow resolves uterine infection by rapid involution of the uterus and cervix, discharge of uterine content, and mobilization of natural host defenses, including mucus, antibodies and phagocytic cells. Clinical signs of uterine infection vary with the virulence of the causative organisms and the presence of factors that predispose to the disease. The treatment of endometritis and metritis in bovine should be directed towards improving fertility. The antibiotic should be active against the main uterine pathogens and should maintain its activity in the environment of the uterus. Also, should not inhibit the normal defense mechanisms and should be well tolerated and not induce irritation in the endometrium. Effective use of hormones in uterine infection requires knowledge of both normal reproductive endocrinology and the therapeutic characteristics of available hormonal preparations.     

Effect of subclinical uterine infection on cervical and uterine involution, estrous activity and fertility in postpartum buffaloes

Nili-Ravi buffaloes (n=29) that calved normally between August and November and did not develop any clinical reproductive disorder after calving were studied for the incidence of sub-clinical bacterial infection of the uterus and its effects on postpartum reproductive efficiency. The incidence of subclinical uterine infection was 24% (7/29). Involution of the cervix and uterus was slower (P < 0.01) in the infected group than in the normal group (45.6 vs 31.1 days and 46.3 vs 35.8 days), respectively. The mean diameters of cervix and gravid horn on Day 12 post partum and on completion of involution did not differ between buffaloes of the two groups. However, the rate of involution of the cervix and the gravid horn was lower in buffaloes of the infected group (2.2 vs. 2.7 mm/day and 2.6 vs. 3.2 mm/day). The mean interval to first post partum ovulation was similar in buffaloes in the infected (35.5 days) and the normal group (33.8 days). The life span of corpus luteum formed after first ovulation was shorter (11 days) in buffaloes of both groups than that of a normal estrous cycle (15 to 17 days). The incidence of silent ovulation was apparently higher in buffaloes of the infected group (83 vs. 60%) but the difference was not significant. For the first four months after calving, the mean interval to first postpartum estrus was longer in buffaloes of the infected group (73.0 vs. 47.7 days; P < 0.01). Similarly, the average service period was longer in buffaloes of the infected group (91.0 vs. 64.8 days; P < 0.05). The overall pregnancy rate for the first four months after calving did not differ between buffaloes of the two groups. We conclude that subclinical bacterial infection of the postpartum uterus delays the cervical and uterine involution which can, in turn, delay the occurrence of first postpartum estrus and prolong the service period in buffaloes.     

The effect of prostaglandin administration to Holstein-Friesian cows at Day 26 postpartum on clinical findings, and histological and bacteriological results of endometrial biopsies at Day 40

Ninety-two cows that calved between April and August 1984 in a commercial dairy herd were studied. The cows were randomly assigned to receive either cloprostenol (500 mug) or saline placebo on Day 26 postpartum. In addition, each cow was examined per rectum, had three endometrial biopsies taken and milk progesterone level determined. Double-blind techniques were used in administering treatments and in assessing response to treatment. The results of histological and bacteriological assessment of endometrial biopsies and clinical findings at Day 40 were compared between the cows that received prostaglandin at Day 26 and those that did not. Each Day 40 variable which was significantly associated with prostaglandin treatment at Day 26 was regressed against the treatment variable and progesterone level at Day 26 as well as a prostaglandin progesterone interaction term. Prostaglandin-treated cows had less vaginal discharge, smaller diameter uterine horns, less inflammation and fibrosis in the endometrium, and were less likely to have Actinomyces pyogenes isolated from a biopsy at Day 40 than untreated cows. These effects were independent of progesterone level at the time of treatment.     

Resumption of ovarian follicular activity and uterine involution in the postpartum llama

Resumption of ovarian follicle activity and uterine involution was studied in the post partum llama. Thirty-nine adult multiparous llamas were monitored by ultrasonography and analysis of urinary estrone sulfate for 30 d post partum at the La Raya Research Station in Peru. Uterine involution was measured in terms of reduction of length and diameter of both uterine horns. Correlation analysis was used to relate follicle size and concentration of estrone sulfate. Analysis of variance was used to determine rate of uterine involution relative to days post partum. The left ovary was palpated and scanned by Day 3 post partum in contrast to Day 1 post partum for the right ovary. Ovulatory size follicles, 7 mm, were present by Day 7.4 post partum (range 4 to 14 d). Follicle growth was detected as early as Day 4 post partum with follicle size being less during the first follicle wave (7.4 mm) compared to the second and third waves (9 to 10 mm). Concentrations of urinary estrone sulfate were positively related (P<0.05) to follicular size, but to a lesser degree during the first follicle wave (19.4 ng/mg Cr), than to the second wave (25.4 ng/mg Cr). Uterine involution, as measured by diameter, was different between the left (gravid) and right (nongravid) uterine horn (P<0.05) for the 17 d post partum, and was also different from that of control females for the 21 d post partum. Uterine involution was complete in 63% of females by Day 21 post partum.     

Uterine involution and ovarian changes during early post partum in autumn-lambing Corriedale ewes

The time of uterine involution and the changes in ovarian follicle populations were studied during early postpartum in multiparous, suckling Corriedale ewes lambing in the autumn. On Day 1 (n=5), Day 5 (n=4), Day 17 (n=4) and Day 30 (n=3) postpartum ewes underwent surgery to obtain ovaries and uteri. The weights of uteri and the lengths of the previous pregnant and nonpregnant horns were recorded as well as the presence of ovarian follicles larger than 1 mm in diameter. Uterine weight and length of uterine horns decreased (P2 to < 4 mm) follicles were also present. At days 17 and 30, aside from the small and medium follicles, all the ewes also had large (>/= 4 mm) follicles, and, at Day 30 2 ewes had large corpora lutea. We conclude that in autumn-lambing Corriedale ewes macroscopic uterine involution was complete around Day 17 post partum and that follicle development begins immediately after parturition, reaching preovulatory size before Day 17. In 2 of the 3 ewes studied until Day 30, ovulation (first progesterone increase) occurred after Day 17 (Days 18 and 25).     

Ability of induced corpora lutea to maintain pregnancy from the third month of gestation to term in cattle

The local relationship between the pregnant uterine horn and the CL during maternal recognition of pregnancy is well-documented. It continues beyond that time; pregnancies were maintained in lutectomized cows when CL were induced on the ovary ipsilateral, but not contralateral, to the uterine horn of pregnancy during Days 28-53. This study evaluated factors affecting maintenance of pregnancy by CL induced after Day 53, in lutectomized cows that had received exogenous progesterone from Day 29 to 15 days after induction of a CL. Twenty-four suckled beef cows were lutectomized on Day 29 of gestation; pregnancy was maintained with progesterone from two controlled internal drug releasing (CIDR) inserts, exchanged every 5 days. Beginning on Day 53, ovaries and viability of pregnancy were evaluated by ultrasonography every 5 days. When a follicle >or=10 mm in diameter was present ipsilateral to the fetus, each cow received 1,000 IU of hCG. Following induction of a CL (20 of 24), progesterone was reduced to a single CIDR for 5 days, then removed. Retention of pregnancy was confirmed by rectal palpation and calving. Cows with induced CL maintained pregnancy to term, including four with the CL contralateral to the fetus. Three cows failed to form normal CL by Day 98 and lost pregnancy after removal of exogenous progesterone. One cow that did not respond to hCG lost pregnancy during exogenous progesterone. In conclusion, CL induced after Day 53 maintained pregnancy to term, even when induced contralateral to the pregnant uterine horn.     

Transuterine sperm transport is not affected by bilateral asymmetry of the reproductive system in dairy cows

Effects of right versus left side activities of the reproductive organs on sperm transport after deep cornual insemination were evaluated in 1686 Friesian cows in their first lactational period. Only single ovulating animals were used. At insemination, semen was deposited deep into the uterine horn ipsilateral or contralateral to the preovulatory follicle. Pregnancy rates were used as measurement of the success of sperm transport. The reproductive history of each cow included that of the side of the previous gestation. A higher activity of the right versus left side was registered. Following calving and after uterine involution, activities of the right versus left side reproductive organs remained constant independently of the side of previous pregnancy, and did not affect transuterine sperm transport. The data indicate that after uterine involution sperm transport is not affected by bilateral asymmetry of the reproductive system in cattle.     

Screening for high fertility in high-producing dairy cows

A retrospective study involving 2756 pregnancies from two commercial dairy herds in northeastern Spain determined relationships between management, production and reproductive data, and high fertility (conception before 90 days in milk) in high-producing dairy cows. High fertility was registered in 989 (35.9%) cows. The following data were recorded for each animal: herd, repeated animal (cows included two or more times within the study in which data were obtained from different lactational periods), parity (primiparous versus multiparous), previous twinning, reproductive disorders following calving (retained placenta, primary metritis) and at postpartum gynecological examination (incomplete uterine involution, pyometra and ovarian cysts), days in milk at conception, previous estrous synchronization and season of calving and conception. In order to evaluate the possible effect of high production during the peak milk yield on subsequent fertility, daily milk production at Day 50 postpartum was also recorded and cows were classified as high (> or = 50 kg) and low (< 50 kg) producers. Logistic regression analysis indicated no significant effects of herd, repeated animal, previous twinning, reproductive disorders such as primary metritis, incomplete uterine involution, pyometra and ovarian cysts, previous estrous synchronization and season of calving and insemination. Based on the odds ratio, the likelihood of high fertility increased in high-producer cows by a factor of 6.8. High fertility was less likely for multiparous cows (by a factor of 0.35) and for cows suffering placenta retention (by a factor of 0.65). High fertile cows produced a mean of 49.5 kg milk at Day 50 postpartum, in contrast to that 43.2 kg milk of the remainder cows. These findings question the negative effect of high production on fertility. Our results indicated that high individual cow milk production can be positively related to high fertility.     

Conceptus-mediated integrity of endometrial epithelial cells and maintenance of relaxin synthesis in pregnant rabbits: effects of unilateral oviduct ligation

A previous study indicated rabbit endometrial relaxin synthesis is stimulated by blastocyst (Lee VH, Fields PA, Biol Reprod 1990; 40:737-745). To evaluate this hypothesis, unilateral oviduct ligations were placed (A) at the oviduct isthmus on Day 1 post-copulation and (B), in a separate group of rabbits, at the infundibulum before copulation. Blastocysts migrate into and implant in the uterine horn contralateral to the ligated oviduct only (conceptus-bearing uterus). The uterine horn ipsilateral to the ligated oviduct will be referred to as the non-conceptus-bearing uterus. Uteri and ovaries were removed on Days 4-28 of pregnancy and were evaluated for relaxin using guinea pig anti-porcine relaxin serum and avidin-biotin light microscopy immunohistochemistry. Results were identical for both models. Blastocysts first attach to the antimesometrial uterine surface by Day 7 post-copulation. Implantation on the mesometrial surface occurs on Days 8-11. Relaxin was observed in antimesometrial endometrial glands of both conceptus and non-conceptus-bearing uteri on Days 4-7 of pregnancy. Beyond Day 7, relaxin was observed in antimesometrial and mesometrial endometrial glandular and luminal epithelial cells at implantation sites of the conceptus-bearing uterus only. Relaxin was not found between implantation sites. Endometrial epithelial cells of the non-conceptus-bearing uterus were regressing by Day 9. These data indicate a conceptus-mediated maintenance of endometrial epithelial cells. Furthermore, the data suggest a paracrine maintenance of epithelial cell integrity and relaxin synthesis since these parameters are preserved only in the conceptus-bearing uterus. Cell-cell communication between conceptus and endometrium appears to be specific since endometrium between implantation sites does not contain relaxin. Uterine tissue from pseudopregnant rabbits (Days 1-16) was evaluated. Relaxin was observed in the antimesometrial glands on Day 7 only. Like the endometrium in the ligation model, endometrial epithelial cells of the pseudopregnant rabbit uterus were regressing by Day 9. These results indicate that pregnancy is not required for, but may enhance, relaxin synthesis. In addition, endometrial epithelial cells regress in the absence of pregnancy. Regression of endometrial epithelial cells on Day 9 suggests that maternal recognition of pregnancy occurs during the preimplantation period (Days 4-8).