Effectiveness of a novel prostaglandin analog in postpartum mares and mares with early season anestrus

Contents Fifty thoroughbred mares, located at Central-Southern Brazil near Sao Paulo (13 anestrous maiden, 18 anestrous barren mares and 19 postpartum mares) were treated with one to three injections, 48 hrs apart, of 2 mg of the novel PGF analog K 11941*, during the early part of the breeding season. Early season anestrus in these problem mares was compounded by the adverse effects of a drought. Plasma progesterone determinations revealed unexpectedly elevated plasma progesterone levels in 61.5% of the maiden mares, in 77.8% of the barren mares and in 68.4% of the postpartum mares (20 to 25 days postpartum). Treatments with K 11941 initiated luteolysis, heat and ovulations in 91.4, 45.5 an 63.3% of these mares, respectively, but initiated also heat and ovulation in 13% and 33% of mares with baseline progesterone levels. Treatments initiated covert and overt cyclic functions in 17 and 12 of those animals which did not conceive immediately. Fifteen animals with recurrent anestrus received further treatment with K 11941. Ten mares cycling silently were force bred when palpations indicated ovulatory follicles, and 7 conceived. Of the 50 mares treated, 38 became pregnant (76%: maiden mares: 76.9%; barren mares: 77.8% and postpartum mares: 73.7%) with breeding indices of 1.9, 1.36 und 1.57, respectively; and 37 mares gave birth to a live foal (74%), At the same stud, 138 control mares had a foaling rate of 82.6%.     

Hydrallantois in two mares

This report describes two mares with hydrallantois. One mare spontaneously entered labor, while the other had labor induced. Uterine inertia necessitated that delivery be assisted in both mares. After delivery, each mare went into hypovolemic shock. One mare survived and the other had to be euthanatized due to rupture of the ventral abdominal musculature with inguinal herniation. The occurrence, diagnosis, treatment and outcome of hydrallantois in the mare are discussed.     

Uterine culture in mares

A guarded, sterile swab is used to obtain samples for uterine culture. With the mare in stocks, the tail bandage and the perineum washed, the culture rod is introduced into the vagina with a gloved hand. After the rod is guided through the cervix, the guard cap is dislodged and the swab is rubbed along the endometrium, after which the rod is extracted. Samples for uterine culture should only be obtained during full estrus. Swabs should be directly plated onto agar within 2 hours of collection. Blood agar is appropriate for initial screening, but use of specialized types of agar expedites identification of microbes. Plates are incubated at 37 C and inspected for growth every 12 hours. The type and number of bacterial colonies should be coupled with the history and clinical signs in deciding on the necessity and type of treatment. Pure, heavy bacterial growth is usually accompanied by clinical signs of infection. Interpretation of the significance of moderate bacterial growth may be aided by cytologic examination of endometrial smears, made by rolling the swab onto a glass slide and staining with Diff - Quik . Large numbers of neutrophils indicate the need for antibiotic therapy. Mixed bacterial growth and variable numbers of neutrophils usually indicate faulty sampling technic. Microaerophilic or anaerobic cultures may aid diagnosis in cases of equivocal aerobic culture results.     

Sexual behavior of mares

Behavior during the estrous phase of the ovulatory cycle of the mare is analogous in most ways to that of estrous females of other species. Proceptive behaviors bring the mare into the proximity of the male and attract his attention. Positioning facilitates mounting, intromission, and ejaculation. Estrous signs appear to be more intense in the few days prior to ovulation than during the transition periods that separate the recurring estrous and diestrous phases. Sexual behavior is absent during diestrus. Detection of estrus in mares is problematic in that it requires the presence (or at least facsimile acoustic or tactile stimuli) or a stallion. Unexplained conditions such as silent or subestrus make reliable determinations even more difficult. The choice of methods for distinguishing estrous from nonestrous mares depends, among other factors, upon characteristics of individual mares, as well as the number of mares to be evaluated. Detection of true estrus--that is, sexual behavior that is associated with follicular growth and ovulation--is confounded by the occurrence of estrus-like behavior independent of gonadal stimulation. Seasonally anovulatory and ovariectomized mares may regularly solicit and accept copulation despite low or even no circulating levels of ovarian steroids. Instead, endocrine support of sexual behavior in these mares appears to be provided by adrenal cortical androgens and/or estrogens. A smaller percentage of pregnant mares may also show some signs of estrus but are not likely to be receptive to mating. The ability of the mare to dissociate sexual behavior from ovulation is unique among infraprimate species studied. The display of estrous behavior and willingness to copulate, even at times when conception is impossible, may have functional significance in promoting band cohesiveness in wild and feral populations. Even without copulation, continued motivation to remain in proximity to the band stallion may contribute to the stability of the social unit outside the ovulatory season.     

Total and partial ovariohysterectomy in seven mares

REASONS FOR PERFORMING STUDY: Ovariohysterectomy appears to have a low mortality rate in mares, but the procedure needs to be reviewed because of the high risk of life-threatening complications. HYPOTHESIS: That ovariohysterectomy can be effective treatment for a variety of uterine diseases in mares and carries a good prognosis. METHODS: Diagnosis, clinical data, surgical technique, post operative care, complications and outcome were recorded from medical records of 7 mares that underwent total (6) and partial (1) ovariohysterectomy at the University of Illinois from 1994 to 2001. RESULTS: The indications for ovariohysterectomy were chronic pyometra (4 mares), chronic uterine torsion (n = 2) and chronic intramural haematoma (n = 1). Surgical exposure was difficult but was improved by traction on stay sutures and right-angled clamps. In some cases, application of the TA-90 autosuture instrument as a right-angled clamp to the caudal part of the uterus improved access to the uterine stump. The most common post operative complications were decreased faecal output, decreased intestinal sounds (4 mares) and mild abdominal pain (2). Two mares had mild to moderate incisional infections. Other previously reported complications, such as haemorrhage, septic peritonitis, uterine stump infection or necrosis, and diarrhoea, did not occur. All mares survived over follow-up periods of 6 months to 5 years and were used for riding (6 mares) and embryo transfer (1 mare, after partial ovariohysterectomy). CONCLUSIONS AND POTENTIAL RELEVANCE: According to this study, the prognosis for mares after ovariohysterectomy appears to be good, despite the technical difficulties of the procedure. The prevalence of life-threatening complications can be lower than reported.     

Clinical biochemistry of pregnant and nursing mares

BACKGROUND: Pregnancy and lactation result in increased metabolic demands. Although homeostatic mechanisms function to keep substances in blood at relatively constant levels, some changes in the concentrations of routine clinical chemistry analytes are likely to occur. OBJECTIVES: The purpose of this study was to determine what physiological changes occur in serum clinical biochemistry analytes in pregnant and nursing mares, and to determine whether the changes were substantial enough to warrant separate reference intervals for pregnant or lactating horses. METHODS: Forty-two Quarter Horse, Thoroughbred, Saddlebred, Standardbred and Morgan mares were entered into the study while pregnant. They were bled once each month through birth. Studies were continued on 20 mares until their foals were weaned. Test results were tabulated by time before or after birth. Serum biochemistry values were determined by standard methods using automated analyzers. Test results were analyzed using the Kruskal-Wallis 1-way ANOVA on ranks. If a significant difference was found (P<.05), Dunn's multiple comparison procedure was performed on all pairs. Results from pregnant and nursing mares also were compared with a reference group of 19 open, nonlactating mares. RESULTS: Serum triglyceride, potassium, creatinine, and total bilirubin concentrations were lower during lactation than during pregnancy. Serum calcium concentration also was slightly decreased at 2 time points during lactation. Triglyceride concentration was highest during midgestation, while bilirubin and creatinine values increased, and potassium and calcium remained constant during pregnancy. Serum urea concentration also remained constant during pregnancy but increased during lactation. Serum phosphate concentration was lowest during midgestation and highest during lactation. Total CO2 values were highest, and anion gaps were lowest, during midgestation. No significant differences were found in serum albumin, globulin, albumin:globulin ratio, total protein, or glucose values. When compared with the reference group of open mares, serum triglyceride, potassium, bilirubin, and total CO2 concentrations were lower, and anion gap was higher in horses that were nursing. CONCLUSIONS: Although most biochemical values remained relatively constant, significant differences were observed during pregnancy and lactation. Changes in the concentrations of triglycerides, potassium, bilirubin, total CO2, and anion gap during lactation were substantial enough to warrant separate reference intervals for lactating horses.     

Sex chromosome mosaicism and infertility in mares

From the standpoint that cytogenetic screening in mares is seldom necessary as an aid to diagnosis of the gonadal dysgenesis syndrome, a series of double-blind trials were conducted to test the proposal that present practice failed to explore the potential for cytogenetics in clinical practice. It was demonstrated that diagnoses of infertility might be made where mares were found to be of normal phenotype by clinical examination. Such mares were found to be gonosmic mosaics. One stallion had a polymorphism of the X chromosome and had poor conception rates. It was demonstrated that the true value of chromosome testing in clinical stud practice has previously been misinterpreted and underestimated.     

Phosphorus excretion by mares post-lactation

Across the equine literature, estimates of true P digestibility range from −23% to 79%. This large range cannot be explained by differences in P intake or phytate-P intake alone. However, differences in endogenous P secretion into the GI tract may explain the variation. In horses, excess absorbed P is not excreted in the urine but is re-secreted into the GI tract, increasing faecal P and leading to estimates of low P digestibility. Thus, accurate estimates of P digestibility can only be obtained if absorbed P is retained in the horse. The objective of this study was to examine P digestibility in post-lactational mares and control mares that were fed similar amounts of P. It was hypothesized that post-lactational mares would have greater P retention and higher apparent P digestibility than control mares. Prior to the study, four lactating and four non-lactating mares were fed a diet that provided 100% of the control mares’ P requirement, but only 55% of the lactating mares’ P requirement. During the study, both groups were fed P at the rate recommended for non-lactating mares. Post-lactational mares did not retain more P than control mares but tended to excrete more P than control mares (p = .082), presumably due to differences in endogenous P secretion into the GI tract. Metabolic changes occurring during mammary gland involution may have contributed to the increase in P excretion. However, faecal P excretion exceeded P intake in both groups (p = .08) and both groups lost weight during the study. Tissue mobilization during weight loss may have influenced P secretion into the GI tract.     

Embryo transfer in subfertile mares

Four subfertile mares (at least 2 barren years) were used as donors in an embryo transfer program. The embryo recovery rate was 50%, varying between 0-100. The transfer of 9 embryos resulted in the pregnancy rate of 44%. The efficiency of embryo transfer using subfertile mares is low. In this material 20% of flushings resulted in a pregnancy.