Ultrasonographic studies on the reproductive tract of mares after parturition: effect of involution and uterine fluid on pregnancy rates in mares with normal and delayed first postpartum ovulatory cycles

During breeding of mares, ultrasonographic detection of uterine fluid accumulations in the first postpartum ovulatory period was associated with significantly decreased pregnancy rates, when compared with rates in control mares (P less than 0.005). The previously gravid uterine horn was recognized as the larger horn, when assessed for size by ultrasonography, for a mean of 21 days (range, 15 to 25 days) after parturition. On the basis of similar measurements obtained during 3 ultrasonographic scans (5-day period), uterine involution was determined to be completed in a mean of 23 days (range, 13 to 29 days). Progestin treatment did not affect uterine size, fluid accumulation, or rate of involution after parturition. However, delaying the first postpartum ovulation with 8 days of progestin treatment significantly improved pregnancy rates (P less than 0.05). More (P less than 0.05) mares became pregnant (23 of 28, 82%) when ovulation occurred after day 15 in the first postpartum ovulatory period, compared with those mares that ovulated before day 15 (6 of 12, 50%). We concluded that ultrasonographic detection of uterine fluid and postpartum progestin treatment can be used to manipulate breeding strategies and to improve pregnancy rates in mares bred during the first postpartum ovulatory period.     

Evaluation of progesterone treatment to create a model for equine endometritis.

To investigate a model for equine endometritis, 12 mares with normal reproductive tracts were divided into 2 groups. All mares received progesterone in oil, 250 mg im, daily. At 5 days after initiation of progesterone administration, the uteri were inoculated with 10(6) colony forming units of Pseudomonas aeruginosa. The day of inoculation was designated Day 0. On Day 6, endometrial swab samples yielded P. aeruginosa in 5 mares; samples from the other 7 mares yielded heavy growth of Escherichia coli, Streptococcus zooepidemicus, Klebsiella pneumoniae, Enterobacter spp., Citrobacter diversus, Staphylococcus epidermidis and Streptococcus morbillorum. On Days 6, 7 and 8, Group A mares received intrauterine infusions of 6 g ticarcillin disodium and 0.2 g clavulanate potassium in 100 ml sterile saline. Group B mares received infusions of saline only. The incidence of swab specimens yielding no bacterial growth was significantly higher in Group A than Group B mares on Days 8 and 13 (4/6 vs 0/6). Swab samples from 5 of the 6 mares in Group A yielded growth of fungi on Days 13 and 19. Mares in Group B were then similarly treated with ticarcillin/clavulanate infusions, on Days 19, 20 and 21. The incidence of swab specimens yielding no bacterial growth was 2/6 and 1/6 on Days 21 and 26, respectively; fungi were not recovered from these mares at any time. The incidence of no-growth swabs after antibiotic treatment tended to be higher in Group A and incidence of fungal recovery after antibiotic treatment was significantly higher in Group A.(ABSTRACT TRUNCATED AT 250 WORDS)     

Uterine involution in mares treated with progesterone and estradiol-17 beta

Bacteriology, histology, and scanning electron microscopy were used to evaluate uterine involution in 27 mares treated with daily injections of 150 mg of progesterone and 10 mg of estradiol-17 beta, commencing within 18 hours of parturition. These findings were compared with those for 24 untreated mares at postpartum day 10 or 11. The treatment resulted in significantly (P less than 0.05) greater uterine gland proliferation. Gland density was significantly (P less than 0.05) greater in mares treated for 6 to 10 days than in those treated 2 to 5 days. The proportion of ciliated cells to secretory cells lining the endometrial surface was significantly (P less than 0.05) greater in mares during delayed foal estrus than in those at postpartum days 10 to 11. The proportion of ciliated to secretory cells increased with increasing duration of treatment. It was concluded that treatment with progesterone and estradiol-17 beta allowed additional time for uterine involution in the early postpartum period.     

Effect of surgical manipulation, placental fluid, and flunixin meglumine on fetal viability and prostaglandin F2 alpha release in the gravid uterus of mares

Twenty-one pregnant mares with single or twin conceptuses between 41 and 65 days of gestational age were allotted to 5 treatment groups. A ventral median celiotomy was performed in all mares. In group-1 mares (3 mares, single conceptus), the uterus and fetus were palpated for 5 minutes. In group-2 mares (3 mares, single conceptus, flunixin meglumine), 250 ml of sterile placental fluid was injected into the nongravid uterine horn. In group-3 mares (4 mares, unicornuate twin conceptuses), group-4 mares (3 mares, unicornuate twin conceptuses, flunixin meglumine), and group-5 mares (8 mares, bicornuate twin conceptuses, flunixin meglumine), 1 conceptus was removed from the uterus via hysterotomy. All mares received progesterone prophylactically until day 100 of gestation or until the fetus died. The 3 mares in group 1 delivered clinically normal, live foals. The mean prostaglandin F2 alpha metabolite (PGFM) plasma concentration peaked at 180 +/- 5.2 pg/ml during uterine manipulation and fetal palpation, then declined to baseline by 1 hour. Free placental fluid (group 2) undermined the chorioallantois ventrally and resulted in fetal death within 3 hours after surgery. The mean PGFM plasma concentration peaked at 39 +/- 4 pg/ml following injection of placental fluid. None of the remaining fetuses in the 7 mares with unicornuate twin conceptuses (groups 3 and 4) survived. Five mares with unicornuate twin conceptuses (group 5) delivered single viable foals. In another mare in group 5, the fetus was alive 4 days after surgery, when the mare was euthanatized for a fractured femur.(ABSTRACT TRUNCATED AT 250 WORDS)     

Acute phase protein response of ewes and the release of PGFM in relation to uterine involution and the presence of intrauterine bacteria.

The rate of uterine involution postpartum was monitored in 13 suckling mule ewes by using radio-opaque markers and radiography, and each ewe was also monitored for intrauterine bacterial contamination during the first week, using a sterile guarded swab. Peripheral plasma or serum concentrations of haptoglobin, seromucoid, ceruloplasmin and 15-keto-13,14-dihydro-prostaglandin F2 alpha (PGFM) were measured up to six weeks postpartum. The maximum reduction in the length of the uterine body and in the diameters of the horns occurred by 28 days postpartum, except in one ewe in which the size of the uterus continued to decrease for 42 days. Four ewes were positive for intrauterine bacterial contamination; Escherichia coli, clostridial species, Staphylococcus aureus, Streptococcus uberis and Enterococcus species were isolated in pure or mixed culture. The presence of intrauterine bacteria did not affect the time for the completion of uterine involution. No bacteria were isolated from the ewe in which involution was delayed, but it had a different acute phase protein response and was therefore excluded from further analyses. In the remaining 12 ewes the mean postpartum haptoglobin response increased, with peak concentrations occurring on day 1, and decreased slowly as uterine involution progressed, but the four contaminated ewes had a significantly greater response. There was no difference between the prepartum and postpartum concentrations of seromucoid in the eight sterile ewes, but significant increases were observed in the contaminated group; the concentrations of ceruloplasmin did not vary in either group. The concentrations of PGFM were higher during the early postpartum period in the ewes with contaminated uteri.     

24-Hour Secretion Patterns of Plasma Oestradiol 17β in Pony Mares in Late Gestation

The mare exhibits nocturnal uterine contractions in the last 6 days of gestation. It is hypothesized that estradiol 17β (O17β) may be associated with the nightly increase in uterine contractions. The 24‐h secretion pattern of plasma O17β was measured in 3 pony mares in late gestation to identify changes in release as the mare neared parturition. Blood was collected weekly at 08:00 hours beginning on day 240 and every third day from day 330 until delivery. Serial blood samples were collected from each mare every 30‐min for 24‐h beginning on gestation day 310 and every sixth day thereafter until parturition. Concentrations of O17β were elevated at night with lowest concentrations occurring directly before sunset (p < 0.01). The natural log of the variance was increased at sunset (p < 0.01) and was decreased during the 6‐h period immediately after sunrise. This pattern was especially evident in the 6 days that preceded parturition. The contrast between nocturnal and daytime concentrations of O17β in the last 6 days of gestation may contribute to night‐time delivery in the mare.     

Supplemental l-Arginine Shortens Gestation Length and Increases Mare Uterine Blood Flow before and after Parturition

Supplementing diets with l-Arginine (Arg) improves female reproductive performance and reproductive blood flow in other species. The objectives of this study were to investigate uterine artery blood flow changes before and after parturition, and evaluate blood flow in Arg supplemented and control mares by Doppler ultrasonography. Sixteen light-horse mares began Doppler ultrasonography evaluation, 21 days before expected foaling date (EFD) and continued until day 7 postparturition. The mares under treatment (n = 8) were supplemented with 100 g Arg, once daily, beginning with 21 days before EFD. Blood flow measurements were calculated as pulsatility index (PI) and resistance index (RI) for both uterine arteries, either ipsilateral or contralateral; to uterine horn of established pregnancy; defined gravid uterine artery (GUA) and non-gravid uterine artery (NGUA), respectively. The mares under treatment had a shorter gestation length (337 ± 1.7 days) as compared to control (345 ± 2.1 days; P ≤ .05). No differences in gestation length were observed between groups when examined by age, parity, EFD, or sex of foal. Both GUA and NGUA uterine artery diameter decreased from the day before parturition to day 7 after parturition (P ≤ .001). During this time period, both PI and RI increased (P ≤ .01); indicating less blood flow. A treatment effect was observed with Arginine-treated mares having greater blood flow prepartum in the NGUA (P ≤ .001) and postpartum in the GUA (P ≤ .05), for both indices. The data demonstrated that supplementing mares with Arg shortened gestation length and increased uterine arterial blood flow before and after parturition.     

Uterine morphology and function in postpartum mares

Ultrasonically detectable characteristics of the uterus and embryo and palpable uterine tone were assessed in 10 postpartum mares. A bright fern-like pattern of ultrasonic uterine echogenicity, outlining the endometrial folds, was observed for an average of 2.1 ±0.2 days following parturition (range, 1 to 3 days). Unexpectedly, the uterus was quiescent throughout the postpartum interval, based on daily one-minute contractility scans. Contractility was maximal on Days 12 to 15 of pregnancy in both postpartum (n=7) and nonparturient (n=7) mares. The mean diameter of ultrasonically detectable intrauterine fluid collections increased (P<0.05) abruptly between days 1 and 2 postpartum and gradually decreased (P<0.05) between days 4 and 7; no collections were detected after day 16. There was no effect of day on echogenicity of the intrauterine fluid collections; on all days, fluid was relatively black or nonechogenic, suggesting that puerperal endometritis was not a problem in this group. Because the increase in intraluminal fluid occurred after parturition and in temporal association with a decrease in diameter and tone of the uterus, the fluid collections apparently represented a physiologic influx from the involuting uterus rather than residual placental fluid. Involution of the horns was completed by day 27 (formerly nongravid horn) and day 31 postpartum (formerly gravid horn), based on failure to detect further significant decreases in diameter. However, the formerly gravid horn was larger (P<0.05) in diameter than the formerly nongravid horn on each of Days 1 to 35 postpartum (end of experiment), indicating residual effects on uterine size. When averaged over both horns, uterine diameters were larger on Days 0 to 24 (Day 0=day of ovulation) of pregnancy in postpartum mares than in nonparturient mares; by Day 25, diameters were similar between statuses. By approximately Day 6 of pregnancy, uterine contractility and ultrasonic endometrial exhotexture were similar between postpartum mares and nonparturient mares. Uterine tone was greater (P<0.05) in postpartum mares than in nonparturient mares on all days between Day 0 and 25. An unexpected, transient increase in uterine tone was detected on Day 5 of pregnancy in both postpartum mares and nonparturient mares. No differences were found between reproductive statuses in patterns of embryo mobility, the day of fixation of the embryonic vesicle (postpartum, Day 15.3 ±0.4; nonparturient, Day 15.0 ±0.3), and diameter of the embryonic vesicle on the day of fixation (postpartum, 22.1 ±1.4 mm; nonparturient, 19.4 ±l.6mm). However, mean uterine tone and mean horn diameters on the side of fixation were greater (cranial and middle cornual segments; P<0.05) or tended to be greater (caudal segment; P<0.1 ) on the day of fixation in postpartum mares than in nonparturient mares. In all postpartum mares, fixation occurred in the formerly nongravid horn. Enhanced uterine tone in postpartum mares may account for the occurrence of fixation on the same day for the two reproductive statuses, despite the larger uterus in postpartum mares.     

Effect of administration of phenylbutazone or progesterone on recovery of embryos from the uterus of mares 5 days after ovulation.

Twelve horse mares were used to investigate the effect of phenylbutazone or progesterone administration on uterine tubal motility, as reflected by embryo recovery from the uterus on day 5 after ovulation. Four treatment groups were used: group A (controls), in which uterine flush was performed 7 to 11 days after ovulation; group B (5-day controls), in which uterine flush was performed 5 days after ovulation; group C, in which uterine flush was performed 5 days after ovulation following administration of phenylbutazone (2 g, IV) on day 3; and group D, in which uterine flush was performed 5 days after ovulation following administration of progesterone in oil (250 mg, IM) on days 0, 1, and 2. Each mare was randomly assigned to each group once. Embryo recovery for each group was: group A, 13 embryos from 12 mares; group B, 3 embryos from 12 mares; group C, 4 embryos from 11 mares; and group D, 1 embryo from 11 mares. Recovery of embryos on day 5 in 3 of 12 nontreated mares indicated that equine embryos may enter the uterus before day 6. Neither treatment increased embryo recovery from the uterus on day 5 over that from the uterus of the 5-day controls.     

Studies on improving the fertility of aged sows. 3. Results of histological studies on puerperal involution and regeneration processes in the endometrium of lactating sows and sows after extremely early weaning]

Involution and regeneration following parturition was studied in 48 sows allowed to suckle their piglets normally, or from which the piglets were taken away at 5-8 days of age. Samples of uterus were obtained by biopsy 4, 8, 11, 14, 17, 20, 30, 32 and 40 days after parturition. In lactating sows, endometrial changes similar to those of oestrus in a normal cycle were present 32 days after parturition. This fact seems to justify the removal of piglets at 21-28 days of age. After very early weaning (5-8 days), incomplete oestrus-like changes in the endometrium were seen on the 17th day after parturition. The observed involutionary and regenerative changes in the puerperal uterus suggest that early weaning after 10-12 days of suckling is feasible, but it may be advisable to use drugs that would accelerate uterine involution.     

Uterine clearance mechanisms during the early postovulatory period in mares

Uterine response to inoculation with Streptococcus zooepidemicus organisms, 51Cr-labeled 15-microns microspheres, and charcoal was evaluated in 9 mares (4 resistant and 5 susceptible to endometritis) to determine mechanical and cellular clearance rates during the early postovulatory period. Mares were inoculated at estrus prior to ovulation during estrous cycles 1, 3, and 5. Uterine swab specimens for aerobic and anaerobic bacteriologic culture and serum for progesterone determination were obtained on postovulation day 3 during estrous cycle 1, on the day of ovulation during estrous cycle 3, and on postovulation day 5 during estrous cycle 5. Immediately thereafter, the uterus was irrigated with 50 ml of sterile physiologic saline solution containing tracer amounts of 125I-labeled human serum albumin. Streptococcus zooepidemicus was isolated from 10 of 15 (67%) uterine specimens collected from susceptible mares and incubated aerobically. Escherichia coli also was isolated from 2 of the 10 specimens incubated aerobically. Anaerobic bacteriologic culture of specimens from all mares yielded no growth. Chromium-labeled microspheres were recovered twice from 2 susceptible mares, on day 0 and day 5. Charcoal was retained in 5 specimens collected from 3 susceptible mares. Bacteriologic culture of specimens from resistant mares did not yield growth. On day 0, chromium-labeled microspheres and charcoal were recovered once from 1 resistant mare. Mares susceptible to endometritis accumulated more fluid within the uterine lumen after ovulation than did resistant mares (mean +/- SEM, 52.73 +/- 15.22 ml and 7.41 +/- 1.96 ml, respectively; P less than 0.01). From this study, it appeared that uterine cellular and bactericidal mechanisms are dysfunctional during the early postovulatory period. However, there appeared to be no disruption of the mechanisms responsible for mechanical clearance of materials inoculated in the uterus.     

Effects of heat stress during pregnancy on postpartum reproductive changes in Holstein cows

Effects of heat stress during the last third of gestation on reproductive changes postpartum were studied in Holstein cows. Cows and heifers 160 to 190 d of gestation were assigned in June 1978 to shade (n = seven cows and two heifers) or no shade (n = eight cows and two heifers) management treatments. After parturition, all cows (n = 19) were moved to the milking herd and managed uniformly. On the day of calving and on each Monday, Wednesday and Friday thereafter until d 50 postpartum, jugular blood samples were collected. Beginning approximately 7 d postpartum, the reproductive tract of each cow was examined rectally after collection of blood samples. Estrus was monitored twice daily and cows were inseminated after d 45 postpartum. Prepartum heat stress increased 13,14-dihydro-15-keto-prostaglandin F2 alpha (PGFM) concentrations postpartum and increased the rate of uterine involution. Regardless of prepartum treatment, progesterone concentrations indicated that luteal phases had begun by d 12.4 +/- 1.3 postpartum, which was about 3 d before PGFM was basal. The first luteal phase lasted only 10.7 +/- .9 d. First estrus was not detected until d 32.3 +/- 4.8 postpartum. The previously gravid uterine horn had a negative effect on ovarian volume, diameter of the largest follicle and percentage of ovaries with a corpus luteum. However, prepartum heat stress attenuated this effect. This study indicates that heat stress prepartum had residual effects on postpartum reproductive changes, and that the previously gravid uterine horn exerted some control, which was attenuated by heat stress, over ovarian recrudescense. Even though heat stress prepartum affected sensitive measures of postpartum reproductive function, it did not alter days to first estrus, days open (102.3 +/- 13.1) or services/conception (2.5 +/- .3).     

PGFM response to exogenous oxytocin and determination of the half-life of oxytocin in nonpregnant mares.

We investigated the half-life of oxytocin in reproductively normal mares and the prostaglandin response after oxytocin administrations. Mares were given oxytocin, 10 or 25 iu, i.v., on the day of, or 2 days after, ovulation, and frequent jugular blood samples were collected for analysis of oxytocin and Prostaglandin F metabolite (PGFM) by RIA. Neither dose of oxytocin nor day of treatment affected the half-life of the exogenous oxytocin, which was determined to be 6.8 min. A significant increase in PGFM was observed within 6 min of oxytocin administration and peak values were observed within 10 min. PGFM response after oxytocin administration on the day of ovulation appeared elevated compared to the response 2 days after ovulation.     

Prostaglandin F2 alpha and prolactin in experimental hypogalactia in sows

Peripheral plasma concentrations of 13,14-dihydro-15-keto-prostaglandin F2alpha(PGFM), progesterone, prolactin and oestrone were determined in 20 sows for two days before and three weeks after parturition. Groups of four sows each received one of the following five treatments post partum: 30 ml sterile 0.9 per cent saline solution intrauterinely; ovariectomy and 30 ml saline solution intrauterinely; 10 ml Lugol's iodine plus 20 ml saline solution intrauterinely; ovariectomy and 10 ml Lugol's iodine plus 20 ml saline solution intrauterinely, or progesterone (0.5 mg [kg bodyweight]-1 intramuscularly). Saline solution and iodine were administered every 48 hours, starting immediately after parturition, for one week. Ovariectomy was performed within eight hours of delivery. Progesterone was given every third day for 12 days. Piglet weight gains were used as a reflection of milk yield. In all sows, oestrone values were elevated before parturition, but fell by the end of delivery and were very low during lactation. PGFM concentrations rose during the last two days of pregnancy to reach maximal values at the time of delivery. Plasma progesterone levels declined concomitantly with the rise in PGFM values before parturition. Basal values of progesterone were achieved within 24 hours after delivery in control sows receiving saline treatment. Progesterone values fell immediately after ovariectomy in sows receiving saline or iodine treatment but were slightly elevated for one week in sows that received only intrauterine iodine treatment, suggesting that complete regression of corpora lutea is prevented by suppression of post parturient uterine prostaglandin production. Sows injected with progesterone maintained plasma values of about 5 to 15 nmol litre-1.(ABSTRACT TRUNCATED AT 250 WORDS)     

Clinical significance of aerobic bacterial flora of the uterus, vagina, vestibule, and clitoral fossa of clinically normal mares

Swab specimens for bacterial culture were obtained from the uterus, vagina, vestibule, and clitoral fossa of 48 mares that had normal reproductive tracts, no history of reproductive problems, and no inflammation on evaluation of endometrial biopsy. The mares were predominantly Thoroughbred and Standardbred. Swab specimens of the vagina were obtained through a sterile speculum; swab specimens of the uterus were obtained by use of a double-guarded, occluded culture instrument. Fifteen (31%) of the uterine swab specimens and 20 (42%) of the vaginal swab specimens yielded growth on aerobic culture; however, only 2 (4%) of the uterine swab specimens and 4 (8%) of the vaginal swab specimens yielded growth of more than 10 colonies. In contrast, 21 (44%) of the vestibular swab specimens and 45 (94%) of the clitoral fossa swab specimens had moderate (greater than 10 colonies in 1 quadrant) to heavy (colonies in 2 or 3 quadrants) growth of organisms on culture. Of organisms considered to be potential pathogens, Streptococcus zooepidemicus and Escherichia coli were found on bacteriologic culture of several clitoral fossa swab specimens and of some vestibular swab specimens. We did not isolate any potential pathogens from uterine or vaginal swab specimens. It appears that 1 to 10 colonies of nonpathogenic organisms could be recovered from the uterus in a substantial number of clinically normal mares even when double-guarded swabbing techniques are used, and we suggest that prebreeding culture requirements be modified to reflect this. Also, our findings indicate that the vulvovaginal fold, rather than the cervix, might be the major barrier to ascending bacterial contamination of the reproductive tract.(ABSTRACT TRUNCATED AT 250 WORDS)     

A radiographic method for measuring the effect of exogenous hormone therapy on uterine involution in ewes.

Twenty-six pluriparous Suffolk ewes were used to monitor the effects of four hormone treatments on the rate of uterine involution, which was assessed by means of radio-opaque markers and radiography. The close correlation between measurements of the genital tract in live sheep and after slaughter indicated that this method of monitoring uterine involution was acceptably accurate. Uterine involution was complete by about 29 days after lambing. None of the hormone treatments with progesterone, oestradiol-17 beta, prostaglandin F2 alpha or an oxytocin analogue, administered shortly after lambing, had any effects on the rate of uterine involution. There was no correlation between the duration of increased plasma concentrations of 13.14 dihydro-15-keto-prostaglandin F2 (PGFM) and the rate of uterine involution.     

Development and Comparison of Sampling Techniques for a Broad Range,Semiquantitative Polymerase Chain Reaction Assay for Detection of Bacterial DNA in the Equine Uterus

Microbial culture from a double-guarded culture swab is commonly used to diagnose infectious endometritis. The objective of this study was to develop a quantitative polymerase chain reaction (qPCR) assay to detect a broad range of bacteria from equine uterine samples. Twenty-seven mares with a clinical history of endometritis had a double-guarded culture swab collected for analysis by qPCR and microbial cultures. An additional 12 mares had a uterine biopsy sample collected for qPCR analysis, microbial culture, and histopathology. Subsequently, a double-guarded culture swab for microbial culture and a cytology brush sample were also collected. The qPCR assay detected bacterial DNA in nine of 27 mares from a double-guarded swab and six of 12 mares from an endometrial biopsy. Positive microbial growth was detected in nine of 27 mares and four of 12 mares from a double-guarded culture swab. Bacterial DNA was detected in two of 27 mares and two of 12 mares without subsequent microbial growth. The simple presence of an organism's DNA allows for detection by nonculture-based systems, both live and dead organisms can be identified. In conclusion, the qPCR assay was determined to be a sensitive diagnostic technique for identifying pathogens associated with infectious endometritis. The primary application of the qPCR assay is detection of potential pathogenic bacteria in the uterus of a mare suspected of having infectious endometritis when a traditional microbial culture is negative. Further work is warranted to determine if mares positive for bacterial DNA and negative for microbial culture are affected clinically.     

Chemotactic properties and protein of equine uterine fluid

Forty uterine fluid samples were obtained from 4 mares classified as resistant to uterine bacterial infection. The uterus of each mare was flushed with 50 ml of saline solution during estrus and diestrus of successive estrous cycles. Bacteria or fungi were isolated from 4 samples, and 7 additional samples were obtained from a mare with active intrauterine infection. Fluid volumes obtained during estrus (means = 40.3 +/- 11 ml) tended to be greater than those recovered during diestrus (means = 36.8 +/- 7.9 ml), but the difference was not significant. Concentrations and yields of protein in recovered fluid did not vary significantly with the day of the estrous cycle. Protein concentration was significantly increased in samples from the infected uterus (P = less than 0.001). The ability of uterine fluid samples to attract neutrophils was measured using chemotactic chambers. There was no significant difference between distances migrated by neutrophils toward fluids obtained during estrus or diestrus. Chemotaxis scores tended to be higher with samples from the infected uterus, and the difference was significant for samples from 2 mares. Chemotaxis was neither significantly correlated with protein concentration of uterine fluid, nor with serum estrogens or progesterone.     

Effect of repeated administration of oxytocin during diestrus on duration of function of corpora lutea in mares

OBJECTIVE: To determine whether IM administration of exogenous oxytocin twice daily on days 7 to 14 after ovulation blocks luteolysis and causes prolonged function of corpora lutea (CL) in mares. DESIGN: Prospective study. ANIMALS: 12 mares. PROCEDURES: Beginning on the day of ovulation (day 0), jugular blood samples were collected every other day until day 40 for determination of progesterone concentration. On day 7, mares (n = 6/group) were treated with saline (0.9% NaCl) solution (control group) or oxytocin. Beginning on day 7, control mares received 3 mL of sterile saline solution every 12 hours, IM, and oxytocin-treated mares received 60 units of oxytocin every 12 hours, IM, through day 14. Mares were considered to have prolonged CL function if progesterone concentration remained > 1.0 ng/mL continuously through day 30. RESULTS: The proportion of mares with prolonged CL function was significantly higher in the oxytocin-treated group (6/6), compared with the control group (0/6). All control mares underwent luteolysis by day 16, at which time their progesterone concentrations were < 1.0 ng/mL. In contrast, all 6 oxytocin-treated mares maintained progesterone concentrations > 1.0 ng/mL continuously through day 30. CONCLUSIONS AND CLINICAL RELEVANCE: IM administration of 60 units of oxytocin twice daily on days 7 to 14 after ovulation was an efficacious method of inhibiting luteolysis and extending CL function in mares. Disrupting luteolysis by administering exogenous oxytocin during diestrus appears to be a plausible and practical method of long-term suppression of estrus in mares.     

Comparison of uterine protein content and distribution of bacteria in the reproductive tract of mares after intrauterine inoculation of Haemophilus equigenitalis or Pseudomonas aeruginosa

Two groups of 3 mares were inoculated with Haemophilus equigenitalis or Pseudomonas aeruginosa on the 1st day of estrus. Uterine flushing samples were recovered on day 3 of estrus and day 8 after ovulation for each cycle. Mares were killed 22, 25, and 30 days after inoculation with P aeruginosa and 45, 46, and 49 days after inoculation with H equigenitalis. Pseudomonas aeruginosa was recovered from the uterus of 2 mares 48 hours after inoculation. Although the initial flushing sample of 1 of these 2 mares had an increased total protein concentration, there appeared to be little difference between protein concentrations of other uterine flushing samples. Haemophilus equigenitalis was recovered from the uterus of each of the 3 mares at postmortem. One mare had a slight, purulent discharge from the vulva. Total protein values were not increased in flushing samples from this mare after inoculation with H equigenitalis. Total protein values decreased in the last flushing sample of each of the 2 remaining mares. Swabbing the uterus was more effective than was homogenizing the uterine mucosa in isolating H equigenitalis.