Factors Influencing the Frequency of Pregnancy Loss among Thoroughbred Mares in Hidaka,Japan

Pregnancy loss in mares is thought to be a main problem associated with reproductive efficiency. To clarify the situation of pregnancy loss in Thoroughbred mares in Japan, the occurrence of pregnancy loss before and after 35 days of gestation was investigated with 1,476 Thoroughbred mares in Hidaka, Japan, from 2007 to 2009. Pregnancy loss on days 17-35 was determined by ultrasound examination between 17 and 35 days after the last mating. Follow-up surveys were conducted between 35 days and foaling to determine pregnancy loss on day 35 until foaling in 843 of these mares. Using multiple logistic regression analysis, we assessed the influence of mare age, reproductive status, twin pregnancy reduction, body condition score (BCS), estrus type in foaling mares (foal heat or not), progesterone therapy, and endometrial cysts on pregnancy loss rates on days 17-35 and on day 35 until foaling in this population of mares. The pregnancy loss rates on days 17-35 and on day 35 until foaling were 5.8% and 8.7%, respectively. The overall pregnancy loss rate (day 17 until foaling, including parturient losses) was 14.7%. Risk factors for pregnancy loss included decrease in BCS between 17 and 35 days, <5 BCS at day 35, mating during foal heat, and endometrial cysts. In all, 14.7% of pregnancies were lost between day 17 and birth, contributing significantly to reduced reproductive efficiency in Thoroughbred mares in Japan. These observations indicate that mares should be maintained at high BCS and should be prevented from mating in foal heat to decrease the pregnancy loss rates.     

Retrospective study on vulvar conformation in relation to endometrial cytology and fertility in thoroughbred mares

Changes in the conformation of the vulva predispose the mare to uterine infection. Vulvoplasty for closure of the upper vulvar lips improves fertility. Not all mares are resutured after parturition, but are resutured after mating. No clinical data have hitherto been published on the reproductive outcome in mares that are resutured or not after parturition. The objectives of the present study were to investigate relationships between vulvar status (not Caslick-operated, group A; previously Caslick-operated and/or not resutured after the last parturition, groups B and C respectively) and endometrial cytology, conception rate and live foal rate for different age groups and categories of Thoroughbred mares. A careful examination of the vulvar area, and endometrial sampling for bacteriology and cytology was performed. The mares were naturally mated once during oestrus (never foal heat) by one of two stallions. Mares belonging to vulvar status group A had the highest conception rate and live foal rate, whereas the lowest conception rate and live foal rate occurred in mares with vulvar status group C. A multifactorial analysis revealed that the vulvar status at arrival had a significant effect on pregnancy rate and live foal rate, but not on fetal loss. Stallion, year and age group had no significant effect on any of the three variables analysed. In conclusion, optimizing managerial factors such as resuturing Caslick-operated mares immediately after parturition to minimize growth of micro-organisms with a subsequent endometritis will contribute to their conception and that they carry a pregnancy to term.     

Videoendoscopic evaluation of the mare's uterus: II. Findings in subfertile mares.

Videoendoscopy of the reproductive tract was performed in 87 Thoroughbred mares with histories of reduced fertility. During hysteroscopy samples for cytological, microbiological and histological examinations were obtained under visual control. Common findings in these broodmares included: (a) endometrial degeneration, as assessed by an uneven distribution or atrophy of endometrial folds and/or a scarred appearance of the endometrium (49 mares, 56%); (b) endometrial cysts of various sizes and locations within the uterus with the most common location being at the base of the uterine horns (48 mares, 55%); (c) fluid accumulation in the uterine lumen (28 mares, 32%). A few mares had transluminal adhesions (7 mares, 8%) and in 2 mares the adhesions appeared to obstruct one uterine horn completely. A solitary discrete lump was detected in the wall of the uterine body in one mare and the suspicion of it being a leiomyoma was confirmed histologically with the aid of a visually directed biopsy sample. Free intraluminal structures were present in the uterine lumen in 3 mares, including one inspissated blood clot and two suspected remnants of resorbing pregnancies. Flexible biopsy forceps and scissors passed through the working channel of the endoscope were used to sever small thin adhesions, but this method proved inadequate for multiple adhesions or cysts. Solitary endometrial cysts were removed by means of conventional rigid biopsy forceps passed alongside the endoscope, although bleeding from the operation site usually limited this type of intervention.     

Cesarean Section in 19 Mares Results and Postoperative Fertility

The case records of 19 mares undergoing caudal ventral midline celiotomy for cesarean section were reviewed. Surgical exposure to the uterus was good, and the incisions healed by first intention in surviving mares. Seventeen mares (89%) survived to time of hospital discharge. Six foals (32%) were delivered alive, of which three were euthanatized because of severe deformity (1 died on day 6 and 2 survived to time of discharge). The most frequent postoperative complications were abdominal pain (13 mares), anemia (10 mares), and retained placenta (6 mares). Sixteen mares were bred during at least one season after the cesarean section and eight (50%) produced at least one foal. The collective foaling rate for these mares, bred a total of 25 seasons, was 36%. Only one mare bred during the same year as the surgery produced a live foal. The collective foaling rate for mares bred after the year of the surgery was 50%.     

Assessment of the breeding prognosis of mares using paired endometrial biopsy techniques

Paired endometrial biopsy samples were taken from 530 subfertile mares, before and after treatment (where indicated) and a period of sexual rest. Prognoses were made after each biopsy (Categories 1A-4A before treatment and Categories 1B-4B after treatment), using histopathological criteria similar to those described by Kenney and Doig (1986). Eighty-seven per cent of the mares were assigned to first biopsy prognosis Category 3A. The second biopsy prognosis produced a more even population distribution (10, 47, 40 and 3 per cent respectively for Category 1B, 2B, 3B and 4B mares). First biopsy Category 3A and 4A mares produced mean foaling rates of 51 and 40 per cent respectively. None of the 14 second biopsy Category 4B mares delivered a live foal (12 were barren, one aborted and one suffered early foetal death). This study supports the hypothesis that a breeding prognosis assigned on the basis of two endometrial biopsy samples, taken before and after specific uterine treatment, where indicated, which takes into consideration the mare's ability to respond to treatment, is likely to be more accurate than one assigned after a single biopsy sample.     

The Effect of Manual Removal of Placenta Immediately after Foaling on Subsequent Fertility Parameters in the Mare

Retained placenta is considered to be a common problem in postpartum mares. The incidence varies from 6% to 54% depending on the breed, with higher incidence in heavy draught mares than in light-weight mares. Retained placenta has been linked to lower postpartum oxytocin concentration, impaired uterine involution, and dystocia. The objective of this study was to assess the effect of early manual removal of placenta immediately postpartum on subsequent fertility parameters (development of free intrauterine fluid, inflammatory status of endometrium, and on pregnancy rates) and to compare them with mares with spontaneous expulsion of placenta. A total of 29 mares, mainly Irish draught, were closely monitored during foaling by closed circuit television and allocated to two groups: (1) mares that expelled the placenta spontaneously within 3 hours of foaling; and (2) mares that were cleansed manually immediately after foal delivery. All mares were examined and scanned 5 and 9 days postpartum, and free intrauterine fluid was recorded; endometrial swabs were taken 9 days postpartum for endometrial cytology and culture. None of the fertility parameters analyzed showed statistical difference between groups 1 and 2. Therefore, it can be concluded that early manual removal of placenta has no detrimental effects on subsequent fertility of mares and, therefore, can be recommended when a veterinarian attends a foaling.     

Surgical Removal of One Conceptus from Fifteen Mares with Twin Concepti

A surgical technique for removal of one conceptus from mares with twin concepti more than 35 days of gestational age was evaluated. One conceptus was removed surgically from each of 15 mares carrying twin concepti that were 41 to 65 days of gestational age. As determined by ultrasonography, eight mares had bicornuate and seven mares had unicornuate twin concepti. For maintenance of pregnancy if surgical trauma should cause prostaglandin release and luteolysis, progesterone was administered prophylactically. Flunixin meglumine was administered perioperatively to minimize prostaglandin release. Five mares with bicornuate twin concepti delivered a single viable foal; in one mare the fetus was alive 4 days after surgery when the mare was euthanatized because of a fractured femur. None of the remaining feti in the seven mares with unicornuate twin concepti survived. The poor survival rate of unicornuate twin concepti was attributed to disruption of the remaining chorioallantois during surgery. Thirteen mares have been rebred successfully.     

A one-stage repair of third-degree perineal lacerations and rectovestibular fistulae in 17 mares.

Third-degree perineal lacerations or rectovestibular fistulae in 17 mares were repaired surgically by a one-stage method. Primary healing occurred in 14 mares; there were one complete dehiscence and two partial dehiscences with fistula formation. Twelve of 13 mares that were bred became pregnant; nine carried foals to term and two are still pregnant. Two mares have each produced one unthrifty foal. One mare repeatedly aborts in the first trimester. Four mares have produced several healthy foals with no further problems. One mare suffered further perineal trauma while foaling.     

Reproductive Performance of Thoroughbred Mares in Sweden

During 1997–2001, a total of 430 Thoroughbred mares were mated by one of the two Thoroughbred stallions on a well‐managed stud farm in the central part of Sweden. On arrival, a thorough gynaecological examination of all mares was performed. An early pregnancy examination was performed on days 14 and 15 after ovulation. The overall conception rates for the two stallions were 92.2 and 88.8%, and the corresponding live foal rates were 82.6 and 75.2%, respectively. The mean number of served oestrous cycles was 1.60 per mare per conception and 1.86 per live foal. The first and second cycle conception rates are reported for different age groups, mare categories and month of mating. The age of the mares had a significant influence on the live foal rate, being lower for mares >13 years of age. Resorption and abortion occurred in higher percentages among mares >8 years of age. The highest embryonic death occurred among mares with a history of being barren, or with having resorbed or aborted foetuses during the previous season. The month of mating had no significant influence on the first cycle conception rate or the second cycle conception rate. The frequency of twinning was 10.5% and the results of manual crushing of one of the conceptuses was successful in 88.9% of all cases, according to the ultrasound scanning 2 days later.     

Cryptosporidium parvum infection in a mare and her foal with foal heat diarrhoea

Cryptosporidium infection was molecularly investigated in mares and in their neonatal foals for which the occurrence of foal heat diarrhoea was also assessed. Thirty-seven mare/foal pairs were included in the study. All foals were born in the same stud farm during 2006-2008 breeding seasons. Two faecal samples, one prior to and one after delivery were collected from each mare, whereas three faecal samples were taken from each foal, i.e. at 8, 10 and 12 days of age. All samples (74 from mares and 111 from foals) were divided into two aliquots, one of which was examined for the presence of Cryptosporidium by a commercially available microplate ELISA kit, while the second aliquot of all ELISA-positive samples was molecularly examined. Nine out of 37 examined foals presented foal heat diarrhoea and one of them scored positive for Cryptosporidium, together with its mare. More specifically, four samples belonging to the same mare/foal pair resulted positive for Cryptosporidium upon both ELISA and PCR. The sequence analysis of the COWP gene showed the occurrence of the zoonotic species Cryptosporidium parvum. The possibility that foal heat diarrhoea-like episodes may be due to neonatal cryptosporidiosis and their relevance for the health of horses and of humans handling diarrhoeic neonatal foals and their mares are discussed.     

Effects of Neodymium:Yttnum Aluminum Garnet Laser Irradiation on Endometrium and on Endometrial Cysts in Six Mares

Effects of neodymium:yttrium aluminum garnet (Nd:YAG) laser irradiation on equine endometrium were evaluated In vitro and in six mares with endometrial cysts. The Nd:YAG laser was applied to six endometrial sites, in each of five uterine specimens, with power densities of 5659 to 33,954 J/cm². Depth of tissue ablation was measured and graded on histologic sections of the tissue lesions. Power density had a significant effect on the depth of tissue ablation (p < .001). Grade 3 lesions (full-thickness ablation of the endometrium) were created with energy densities of 16,977 to 33,954 J/cm². Six mares had endometrial cysts treated by photoablation. Two of the four mares that were reproductively sound but barren, despite appropriate breeding, produced foals after treatment. One mare remained reproductively unsound after treatment, and another mare that was treated postpartum was bred successfully.     

Molecular confirmation of an abortigenic strain of equine herpesvirus 1 (subtype 1) in a pregnant mare study

Four pregnant mares were inoculated intranasally and/or intravenously with equine herpesvirus 1 (EHV-1), subtype 1 during the third trimester of gestation. One mare aborted on postinfection day 15, one mare delivered a sick, weak full term foal, and two mares delivered healthy, full term foals. EHV-1, subtype 1 was isolated from several tissues of the aborted fetus and from the thymus of the sick foal. DNA restriction endonuclease patterns of the recovered EHV-1 viruses were identical to those of the EHV-1 challenge strain, documenting the origin of the abortigenic viruses.     

Relation Among Neutrophil Enzyme Activity,Lipid Peroxidation,and Acute-Phase Response in Foal Heat in Mares

Apart from functional abnormalities, genetic structural disorders and management problems endometritis is one of the major causes of infertility or subfertility in mares. However, the causes of postbreeding endometritis in foal heat have not been clearly resolved to date. The aim of this study was to search for the relationship between neutrophil activity, acute-phase proteins, and oxidative status to indicate the parameters, which can influence fertility in cold-blooded mares in foal heat. The blood for the experiment was collected from 16 cold-blooded mares at five time points: 6–8 days before parturition, 24 hours after parturition, at the first postpartum breeding on the ninth day, 24 hours after breeding, and 48 hours after ovulation. The obtained samples were assigned for hematological tests, assays of neutrophil activity, plasma malondialdehyde (MDA), and fibrinogen concentrations. We estimated that in susceptible mares during persistent postbreeding endometritis, neutrophil activity increased together with MDA and fibrinogen plasma level. Elastase release in resistant mares before parturition was 48.91 ± 1.75%, whereas in susceptible animals, the value reached 45.57 ± 1.9% of the maximal release. Myeloperoxidase release in resistant mares before parturition reached 13.95 ± 2.1%, then increased at three consecutive measurements, and returned to a value from before parturition at the last measurement. Myeloperoxidase level in susceptible mares was slightly lower than in resistant ones, then these values augmented at all measurements, reaching the maximum at the fourth one. The obtained results may help to indicate the predisposition to persistent postbreeding endometritis in cold-blooded mares bred at foal heat.     

Comparison of endometrium before and after repair of third-degree rectovestibular lacerations in mares.

The endometrial response of mares to repair of third-degree rectovestibular lacerations was evaluated. Endometrial biopsy specimens from 8 mares with third-degree rectovestibular laceration were obtained immediately before surgery and from 9 to 15 days after repair. Presurgical endometrial biopsy specimens were classified as category I for 2 mares; category II, attributable to slight endometritis, for 5 mares; and category III, attributable to moderate-to-severe endometritis, for 1 mare. Within 15 days after rectovestibular repair, all endometrial biopsy specimens were classified as category I. Results indicated that mares with third-degree rectovestibular injuries are candidates for breeding by artificial insemination by 2 weeks after repair of the injury.     

Preliminary studies of mammary secretions in the mare to assess foetal readiness for birth

The status of the mare and foetus in relation to readiness for birth was assessed by measurement of the electrolytes sodium, potassium and calcium in mammary secretions pre-partum. Sixteen Thoroughbred mares were allowed to foal spontaneously and the ionic status of their mammary secretions was measured over three to five weeks pre-partum. From these measurements, a scoring system was developed where an ionic score of 35 points or more suggested that the mare was within 24 h of foaling. On the basis of this ionic score, 10 pony mares were induced with either oxytocin or fluprostenol and assessment of foal maturity was made by physical, behavioural and physiological criteria. Eight pony mares, induced when the ionic score was 35 points or more, delivered full term foals; two mares were induced when their scores were 30 and 20 points and delivered a full term and slightly immature foal respectively. These results suggest that foetal maturity may be related to electrolyte concentrations in mammary secretions and that an ionic score of 35 points or more may indicate that induction would be successful in terms of maturity of the newborn foal.     

Fertility at the first post partum estrous compared with fertility at the following estrous cycles in foaling mares and with fertility in nonfoaling mares

A retrospective study on the reproductive performance of 401 artificially inseminated trotter mares during six breeding seasons is presented. Mares, 279 post partum (PP) and 122 maiden and barren, or nonlactating (NL), were inseminated with fresh semen obtained from four fertile stallions of the same breed. Pregnancy rate (PR) of mares inseminated at the foal heat (182/253, 71.9%) was lower, but not significantly different, than the PR (22/26, 84.6%) of mares inseminated for the first time at the second post partum cycle and similar to the PR at the first and second cycle of NL mares (95/112, 77.8% and 25/33, 75.7%, respectively). PR of mares inseminated at the foal heat was higher, but nonsignificantly different, from PR of the post partum mares not pregnant after artificial insemination (AI) at foal heat and inseminated again at the following estrous cycle. The PR after AI at the foal heat was significantly higher than the PR when the AI was performed at the third or later cycle in NL mares (71.9% vs 22.2%, P<0.01). The estrus cycle/pregnancy ratio for the PP mares inseminated, for the first time at the foal heat or at the second heat and for NL mares was, respectively, 1.4, 1.2, 1.3 at first cycle and 1.4, 1.3 and 1.4 at the end of the season or when mares left the stud. The proportion of open mares at the end of the season or when leaving the stud was 7.1% (18/253), 3.8% (1/26) and 4.1% (5/122) for PP mares first inseminated at the first or second post partum cycle and for NL mares, respectively; the total rate of open mares was 6% (24/401). The foaling rate (FR) following conception at the foal heat (72.1%) was not statistically different from the FR following conception at any other cycle (50–100%). Based on the absence of significant differences in fertility at the first post partum estrus cycle versus any other estrus cycle, we conclude that breeding at the foal heat should be advisable.     

The Pattern of Embryonic Fixation and its Relationship to Pregnancy Loss in Thoroughbred Mares

Ultrasonographic pregnancy records of 195 mares from six Thoroughbred stud farms, over a period of 7 years were retrospectively analysed to assess the effect of various factors on embryonic vesicle (EV) fixation pattern and pregnancy outcome. Of the total of 746 pregnancies analysed, significantly (p < 0.01) more EV fixations were evident in the right uterine horn than in the left (53.35% vs 46.65% respectively). There was no significant effect of either, the side of ovulation, or age of the mare, on the side of EV fixation. However, EV fixation, was significantly (p < 0.001) more likely to occur in the right uterine horn in maiden and barren mares (65.75% vs 57.45% respectively). The age and reproductive status of the mare as well as foal heat breeding failed to demonstrate a consistent effect on pregnancy loss relative to the side of EV fixation. In lactating and foal heat bred mares, EVs were significantly (p < 0.0001) more frequently established in the contralateral horn to the one from which the mare delivered her most recent foal. In lactating mares, significantly (p < 0.05) higher embryonic and pregnancy losses were observed in the ipsilateral horn. In conclusion, (a) side of EV fixation was (i) independent of the side of ovulation and mare age (ii) significantly (p < 0.001) affected by reproductive status, (b) neither age of mare nor reproductive status had any effect on pregnancy loss rates relative to the side of EV fixation and (c) in lactating mares the EV had a greater chance of fixation and survival in the horn contralateral to the one from which the mare delivered her most recent foal.     

Outbreak of equine herpesvirus type 1 myeloencephalitis: new insights from virus identification by PCR and the application of an EHV-1-specific antibody detection ELISA

Five of 10 pregnant, lactating mares, each with a foal at foot, developed neurological disease. Three of them became recumbent, developed complications and were euthanased; of the two that survived, one aborted an equine herpesvirus type 1 (EHV-1)-positive fetus 68 days after the first signs were observed in the index case and the other gave birth to a healthy foal on day 283 but remained ataxic and incontinent. The diagnosis of EHV-1 myeloencephalitis was supported by postmortem findings, PCR identification of the virus and by serological tests with an EHV-1-specific ELISA. At the time of the index case, the 10 foals all had a heavy mucopurulent nasal discharge, and PCR and the ELISA were used to detect and monitor EHV-1 infection in them. The status of EHV-1 infection in the five in-contact mares was similarly monitored. Sera from three of the affected mares, taken seven days after the index case were negative or had borderline EHV-1-specific antibody titres. In later serum samples there was an increase in the titres of EHV-1-specific antibody in two of the affected mares. In contrast, sera from the five unaffected in-contact mares were all EHV-1-antibody positive when they were first tested seven or 13 days after the index case.     

A preliminary investigation of the use of a foal image to reduce mare stress during mare–foal separation

The data for this study were collected from 7 mares (10 ± 1.6 years old) when their foals were 4-, 15-, 30-, 45-, or 60-days-old. On each occasion, the foals were anesthetized and placed out of sight of the mare and the mares’ behavior, heart rate, and cortisol response to foal separation in either the presence of a foal phantom, a square shape, or no visual stimuli were measured. In the presence of the foal phantom, anxious (P = 0.119) and agitated (P = 0.524) mare behavior was not significantly different from baseline values. The mares had significantly elevated behavior scores for 5 out of 6 criteria when the square phantom was presented and were significantly more active (higher scores for fidgety and active criteria) when no visual stimuli (control) were provided. Based on the data presented in this study, the use of a phantom image of a foal with neutral ear and tail position may be an effective nonchemical method of calming mares during separation from their foal.     

Effects of restrictive suckling on postpartum reproductive performance in mares

Quarter Horse mares (n = 30) and their foals were used in a 2-year study. Objectives of the study were (i) to determine the effects of a treatment regimen, which permitted nursing for four 1-hour periods each day, on the postpartum reproductive performance of the dams, and (ii) to assess the effects of this procedure on the growth and development of foals. Mares in the restricted suckling treatment group showed estrus and ovulated sooner (P less than 0.01) after parturition than did control mares during the first year of the study, but not during the second year. Plasma progesterone concentrations were similar for both treated and control mares and remained less than 1 ng/ml from parturition to ovulation. Conception rates were not significantly influenced by treatment. However, two mares which had records of failing to have estrus while nursing a foal were bred and ovulated, and one of the two conceived while on the restricted suckling treatment. The absence of treatment effects on any of the variables measured in the foals indicates that restricted suckling did not impair foal growth and development.