Diagnosis and management of abnormal embryonic development characterized by formation of an embryonic vesicle without an embryo in mares

OBJECTIVE: To determine the incidence, ultrasonographic characteristics, and risk factors associated with embryonic development characterized by formation of an embryonic vesicle without an embryo in mares. DESIGN: Prevalence survey. ANIMALS: 159 pregnant mares. PROCEDURES: From 1994 to 1998, mares between 11 and 40 days after ovulation with normal and abnormal embryonic development were examined ultrasonographically, and characteristics of each conceptus were recorded. RESULTS: The incidence of abnormal embryonic development in mares characterized by formation of an embryonic vesicle without an embryo was 7/159 (4.4%) during the 5 breeding seasons. Age and breed of mare or type of semen used did not differ for mares with normal and abnormal embryonic development. The percentage of mares in which the conceptus was undersized during > or = 1 examination was significantly higher for mares with abnormal conceptuses (5/7), compared with mares with normal conceptuses (2/147; 1.4%). The percentage of examinations during which the conceptus was undersized was significantly higher for abnormal conceptuses (12/27; 44.4%), compared with normal conceptuses (4/448; 0.9%). CONCLUSIONS AND CLINICAL RELEVANCE: To diagnose an embryonic vesicle without an embryo, mares should be examined by use of transrectal ultrasonography on day 25 after ovulation. When an embryo cannot be identified at that time, mares should be reexamined at intervals of 1 to 3 days until day 30. Because undersized conceptuses are more likely to be abnormal, development of undersized conceptuses should be monitored closely.     

Strategies for Using eFSH for Superovulating Mares

The standard treatment for superovulation of mares is to administer equine follicle-stimulating hormone (eFSH) for 4 to 5 days to stimulate multiple follicles and human chorionic gonadotropin (hCG) to induce synchronous ovulations. Objectives of this study were: (1) to determine whether a short-term (3-day) eFSH treatment protocol would result in similar ovulation and embryo recovery rates compared with the standard eFSH protocol; (2) to determine the efficacy of a decreasing dose of eFSH (step-down protocol) on ovulation rate and embryo recovery; (3) to compare the efficacy of hCG and recombinant equine luteinizing hormone (reLH) for inducing ovulation in FSH-treated mares; and (4) to compare embryo recovery rates and embryo size when mares are flushed at 6.5 or 7.0 days after ovulation. Forty light-horse mares were used in 2005 (experiment 1) and 20 different mares were used in 2006 (experiment 2). In experiment 1, mares were randomly assigned to one of three treatment groups: (1) untreated controls, (2) standard eFSH treatment (12.5 mg intramuscularly twice daily), and (3) 3-day eFSH treatment. In experiment 2, mares were randomly assigned to one of four treatments: (1) untreated controls, (2) standard eFSH protocol, (3) 3-day eFSH treatment, and (4) step-down eFSH treatment (12.5 mg twice daily day 1, 8.0 mg twice daily day 2, 4.0 mg twice daily day 3). Within each treatment, mares were given either hCG (2,500 IU) or equine LH (750 mg, EquiPure LH; reLH) to induce synchronized ovulations. Embryo recovery was performed either 6.5 or 7.0 days after ovulation. In experiment 1, numbers of preovulatory follicles and ovulations were less for mares in the 3-day treatment group than the standard group, but were greater than for controls. Embryo recovery per flush was higher in the standard group (2.6) than the 3-day eFSH treatment (0.8) or control groups (0.8). In experiment 2, the number of preovulatory follicles and number of ovulations were greater in the standard and 3-day treatment groups than in control and step-down groups. The percent embryo recovery per ovulation and mean embryo grade were similar for all groups; however, the embryo recovery per flush was higher for mares in the standard treatment than controls (1.3 vs 0.6) but was similar to the 3-day (1.1) and step-down (0.8) treatments. Embryo recovery was similar for flushes performed on days 6.5 and 7.0 post-ovulation. The percentage of control mares ovulating within 48 hours in response to hCG or reLH was similar. In contrast, a higher percentage of eFSH-treated mares ovulated within 48 hours in response to reLH than hCG (92% vs 71%). In both years, the 3-day eFSH treatment protocol resulted in a greater number of preovulatory follicles and a greater number of ovulations than untreated controls. Unfortunately, the increased ovulation rate for mares administered eFSH for 3 days did not result in a greater number of embryos recovered per flush in either year. Use of a step-down eFSH treatment protocol resulted in fewer preovulatory follicles, fewer ovulations, and fewer embryos as compared with the standard eFSH treatment. In conclusion, the standard eFSH treatment resulted in a greater embryo recovery rate per cycle than either the 3-day or step-down treatment protocols. Recombinant equine LH was more effective than hCG in causing ovulation in eFSH-treated mares.     

Comparison of androst-16-ene steroid levels determined by a colorimetric assay with boar taint estimated by a trained sensory panel

A group of 17 intact male pigs and 3 gilts ranging in weight from 96 to 260 kg was selected for sensory evaluation of boar taint in loin chops. Samples were evaluated by 10 trained judges using a 10-cm graphic scale for rating off-aroma, off-flavor, pork flavor, softness, tenderness, juiciness, and residual tissue. In addition, a fry test for taint was conducted by four experienced testers on fat samples from all animals. Androst-16-ene steroid levels were measured in salivary gland and fat. Two versions of a colorimetric assay for the androst-16-ene steroids were used, a complete version, in which cholesterol was removed from the tissue extracts using a digitonin-Sepharose affinity column, and a simplified version, which does not include this step. The off-aroma and off-flavor sensory scores showed a good correlation with the androst-16-ene levels in fat and salivary glands and high correlations were obtained between the androst-16-ene steroid levels in fat and salivary glands. The levels of the androst-16-ene steroids in the salivary gland were highly correlated with the levels of estrogen in the blood and to a lesser extent with the levels of testosterone in the blood. Similar correlation coefficients were obtained between salivary gland androst-16-ene steroid levels measured using either the complete or simplified versions of the colorimetric assay and the off-aroma and off-flavor sensory scores. The results of the fry test were variable and no statistically significant correlations were obtained between the fry test results and the off-aroma and off-flavor sensory scores from the trained sensory panel.(ABSTRACT TRUNCATED AT 250 WORDS)     

Hormone therapy for control of reproduction in mares and stallions

Because the reproductive performance of mares is lower than that of any other domesticated species, hormone therapy is important in ensuring fertility and proper management of pregnancy. Current techniques of hormone therapy are discussed.