W.B. Ley

Oklahoma State University - Stillwater, Stillwater, Oklahoma, United States

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Publications (42)36.34 Total impact

  • J. J. Dascanio · Schweizer CL · W. B. Ley
    No preview · Article · Jan 2010
  • [Show abstract] [Hide abstract] ABSTRACT: The in vitro production (IVP) of equine embryos using currently available protocols has met limited success; therefore investigations into alternative approaches to IVP are justified. The objective of this study was to evaluate the feasibility of xenogenous fertilization and early embryo development of in vitro matured (IVM) equine oocytes. Follicular aspirations followed by slicing of ovarian tissue were performed on 202 equine ovaries obtained from an abattoir. A total of 667 oocytes (3.3 per ovary) were recovered from 1023 follicles (recovery rate, 65%). Oocytes underwent IVM for 41 +/- 2 h (mean +/- S.D.), before being subjected to xenogenous gamete intrafallopian transfer (XGIFT). An average of 13 +/- 0.8 oocytes and 40x10(3) spermatozoa per oocyte were transferred into 20 oviducts of ewes. Fourteen percent of transferred oocytes (36/259) were recovered between 2 and 7 days post-XGIFT and 36% of those recovered displayed embryonic development ranging from the 2-cell to the blastocyst stage. Fertilization following XGIFT was also demonstrated by the detection of zinc finger protein Y (ZFY) loci. Ligation of the uterotubal junction (UTJ), ovarian structures, or the duration of oviductal incubation did not significantly affect the frequency of embryonic development or recovery of oocytes/embryos after XGIFT. In conclusion, equine embryos can be produced in a smaller non-equine species that is easier for handling.
    No preview · Article · Feb 2004 · Theriogenology
  • [Show abstract] [Hide abstract] ABSTRACT: Tetanus antitoxin (TAT) was given to 39 horses (1500 IU) intramuscularly; 39 horses (1500 IU) subcutaneously; and 20 horses (25,000 IU) intravenously. Horses were evaluated for clinical evidence of hepatic disease before administration of TAT and on days 1, 2, 14, 60, and 120 after injection. Blood was collected on days 0, 1, 60, and 120 from 9 horses that received TAT by the subcutaneous or intramuscular route, and 5 horses that received TAT intravenously. Serum chemical analysis, which included measurement of total bilirubin concentration, and activity of gamma-glutamyltransferase, aspartate transaminase, and sorbitol dehydrogenase, was performed on the samples. All horses remained clinically normal throughout the 120-day postinjection period. On days 60 and 120 post-IM or SC administration, a statistically significant increase in mean gamma-glutamyltransferase serum concentration was observed compared with pretreatment concentrations, but these values did not exceed the normal reference interval. All other indices did not significantly increase throughout the study. Individually, only one horse had a slight elevation in SDH concentration on day 60 and 120. These findings suggest that administration of TAT rarely causes overt hepatic disease or persistent elevation of hepatic serum indices, regardless of the route of administration.
    No preview · Article · May 2003 · Journal of Equine Veterinary Science
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    [Show abstract] [Hide abstract] ABSTRACT: Horses that are exposed to Sarcocystis neurona, a causative agent of equine protozoal myeloencephalitis, produce antibodies that are detectable in serum by western blot (WB). A positive test is indicative of exposure to the organism. Positive tests in young horses can be complicated by the presence of maternal antibodies. Passive transfer of maternal antibodies to S. neurona from seropositive mares to their foals was evaluated. Foals were sampled at birth (presuckle), at 24h of age (postsuckle), and at monthly intervals. All foals sampled before suckling were seronegative. Thirty-three foals from 33 seropositive mares became seropositive with colostrum ingestion at 24h of age, confirming that passive transfer of S. neurona maternal antibodies occurs. Thirty-one of the 33 foals became seronegative by 9 months of age, with a mean seronegative conversion time of 4.2 months. These results indicate that evaluation of exposure to S. neurona by WB analysis of serum may be misleading in young horses.
    Full-text · Article · Mar 2001 · Veterinary Parasitology
  • No preview · Article · Mar 2000 · Journal of the American Veterinary Medical Association
  • No preview · Article · Mar 2000 · Journal of the American Veterinary Medical Association
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    [Show abstract] [Hide abstract] ABSTRACT: Like the human female, the mare experiences reproductive tract pathology that may sometimes be circumvented by the use of assisted reproductive technologies (ARTs). One such technology, gamete intrafallopian transfer (GIFT), may be used in mares that exhibit ovulatory, oviductal, or uterine abnormalities that limit the use of common ARTs, such as embryo transfer. Homologous GIFT has been successfully performed in the horse; however, the logistics, costs, and associated risks of surgically transferring gametes to the oviducts of a recipient mare are considerably high. Use of a less costly species in a heterologous or xenogenous procedure would therefore be beneficial. This study represents the preliminary investigation into the use of sheep as recipients for xenogenous GIFT procedures using equine gametes. We investigated the capacitation response of fresh, cooled, or frozen stallion sperm after 1) in vivo incubation in the reproductive tract of estrous and anestrous ewes as well as 2) in vitro incubation in a modified Krebs/ Ringer extender at 37 degreesC with and without the addition of heparin at 10 IU/mL for up to 8 hours. A chlortetracycline (CTC) fluorescent stain was used to assess the capacitation response of sperm. Findings indicated that oviductal fluid samples recovered from estrous ewes had significantly higher numbers of sperm exhibiting capacitation-like staining patterns when compared to samples recovered from anestrous ewes (P < .05). Fresh semen yielded higher capacitation-like staining patterns after in vivo incubation than did frozen-thawed or cooled samples. A transition from majority CTC unreacted sperm to majority CTC non-acrosome intact sperm was demonstrated for both in vivo and in vitro studies. In vitro incubation of stallion sperm with heparin did not result in an increased capacitation-like staining response over time when compared with nonheparinized samples. Results from this study suggest that xenogenous capacitation of stallion sperm may occur in the estrous ewe.
    Full-text · Article · Jan 2000 · Journal of Andrology
  • [Show abstract] [Hide abstract] ABSTRACT: This is the third and final article of a three-part Continuing Education Series on reproductive diagnostics in mares. Hormonal evaluation and genetic testing are procedures that should be performed on mares that are presented with infertility that has not been diagnosed by means of previous testing. In addition to making a diagnosis, veterinarians may decide to pursue further tests in order to confirm previous findings, to determine a prognosis, or to select therapeutic options. The first article in the series discussed basic reproductive evaluation in mares, including external conformation evaluation, palpation of internal genitalia per rectum, ultrasonography of the reproductive tract, vaginoscopy, and manual vaginal/cervical/uterine examination. The second article considered uterine culture, cytology, and biopsy; hysteroscopy; oviductal patency testing; and scintigraphy. Sample collection for hormonal evaluation and genetic testing involves procedures that veterinarians can perform in their practices. Inhibin, equine chorionic gonadotropin, estrone sulfate, progesterone, estradiol, and testosterone are the hormones of interest in reproductive diagnostics in mares. At various laboratories, multiple hormonal packages and single assays are available to practitioners. Genetic testing should be performed when the cause of infertility is unresolved. XO and 64,XY gonadal dysgenesis are among the most common genetic disorders that result in infertility in mares.
    No preview · Article · Jun 1999
  • [Show abstract] [Hide abstract] ABSTRACT: A study was conducted to investigate the effect of magnesium sulfate solution on the equine endometrium using 7 treatment mares and 3 control mares. Treatment mares were infused with 128 grams of magnesium sulfate in one liter of 0.9% sodium chloride, while control mares were infused with one liter of 0.9% sodium chloride. Reproductive examinations, including palpation and ultrasound examination per rectum of internal genitalia, vaginoscopy, uterine culture, uterine cytology, endometrial biopsy, and hysteroscopy, were performed 12 days prior to infusion and days 1, 7 and 21 after infusion. Serum magnesium concentrations were assessed at 0, 1, 2, 4, 6, and 12 hours post-infusion. The only statistically significant findings in assessed reproductive parameters was a more cloudy vaginal discharge and a higher biopsy score in control mares on day 1 post-infusion. These findings were not present at the day 7 or 21 observation periods. This study demonstrates that intrauterine magnesium sulfate, used at the concentration described, did not result in harmful effects detectable by the parameters evaluated. It should be noted that assessment of the effect of magnesium sulfate on specific uterine pathologies or fertility was not made.
    No preview · Article · Jun 1998 · Equine practice
  • Ts Donrov · D Batsaihan · W. B Ley
    [Show abstract] [Hide abstract] ABSTRACT: Pregnant mares' serum (PMS) was prepared from blood collected from native Mongolian mares between 60 and 70 days of gestation. Pregnant mares' serum gonadotropin (PMSG; potency of 400 IU/mg) was extracted from PMS by precipitation in graded concentrations of ethanol in a stepwise fashion. The equivalent of 600 IU PMSG as native PMS was administered to Mongolian ewes (group A; n=106) at 7-day intervals for a treatment period of 21 days to induce estrous. The same was accomplished in 60 ewes (group B) using 600 IU PMSG extract. A third group of ewes (group C; n=123) served as untreated controls during the same time period. Onset of estrous was assessed by daily introduction of vasectomized rams. Ewes determined in estrous were bred by natural service during the subsequent 12 h by one of several fertile rams. Each ewe was allowed exposure to fertile rams only once for the duration of this trial. Estrous was detected in 65.1%, 71.7% and 26.1%, respectively, in groups A, B and C, by the end of the second week of the trial. Groups A and B were not different, but group C had fewer (P
    No preview · Article · Apr 1998 · Small Ruminant Research
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    Full-text · Article · Jan 1998
  • Wynne A. DiGrassie · William B. Ley
    No preview · Article · Oct 1997 · Journal of Equine Veterinary Science
  • [Show abstract] [Hide abstract] ABSTRACT: Basic examination of the reproductive system of a mare should include external conformation evaluation, palpation of internal genitalia per rectum, ultrasonography of the reproductive tract, vaginoscopy, and manual vaginal/cervical/uterine examination. These procedures were described in the first part of this three-part Continuing Education Series. In addition, evaluation of the reproductive system may require performing uterine culture, uterine cytology, and uterine biopsy. Because bacteria may be recovered from the uterus of normal mares that are in estrus, uterine culture should be evaluated in conjunction with uterine cytology to increase the accuracy of diagnosis. Uterine biopsy should be examined in patients with chronic reproductive disorders to document persistent endometrial pathology. More advanced diagnostic procedures, which may require referral to a specialty practice or university, include hysteroscopy, oviductal patency testing, and scintigraphy. These procedures are generally not required during routine reproductive evaluations but are useful when prior diagnostic procedures do not fully describe the condition that is affecting the mare. If a definitive diagnosis is still not achieved after the reproductive system of a mare has been evaluated by these basic and advanced procedures, hormonal evaluation and genetic testing may be required; the third and final article in this series will consider these two diagnostic approaches.
    No preview · Article · Sep 1997
  • [Show abstract] [Hide abstract] ABSTRACT: Evaluation of the female reproductive tract requires knowledge of the basic diagnostic procedures that are involved. Examination may be performed to identify lesions, to describe normal reproductive events that are associated with breeding and pregnancy, or to ensure that the reproductive tract is normal. Examination should proceed in a systematic manner, starting with external conformation evaluation, palpation of internal genitalia per rectum, ultrasonography of the reproductive tract, and vaginoscopy and/or manual vaginal/cervical/uterine examination. The first article of this three-part continuing education series considers these specific procedures used to evaluate the reproductive system of the mare. After the basic reproductive examination has been completed, the information gathered can be summarized to reach a diagnosis or to suggest the need for ancillary diagnostic approaches. It is possible for the veterinarian to arrive at a faulty conclusion by considering only one piece of information gleaned from the basic examination. If all of the information fails to clearly indicate the condition that is affecting the mare, further diagnostic procedures should be considered. These procedures are reviewed in the remaining two parts in this series. The second part will deal with uterine culture, uterine cytology, uterine biopsy, hysteroscopy, oviductal patency testing, and scintigraphy. The final article will discuss hormonal evaluation and genetic testing.
    No preview · Article · Aug 1997
  • [Show abstract] [Hide abstract] ABSTRACT: The effect of temperature, total milk solids, milk fat, milk lactose, and milk protein on the prediction of colostral immunoglobulin from colostrometer specific gravity readings was studied using a colostrometer with a 15-ml sampling chamber and a radiator bulb hydrometer. Colostral sample results from 30 mares were used to develop an equation to correct specific gravity for variations in water temperature [IgG = (-83000) + (84700 x specific gravity) - (46 x water temperature (°C)]. Although the prediction of immunoglobulin was improved by including milk components, only temperature was included in the equation, since the other parameters are not routinely analyzed in farm situations. The results indicated that the temperature of the colostrometer water column can affect specific gravity readings and that correction for this effect can be made using the developed equation. Colostrum temperature variation within the colostrometer's pycnometer did not have a practical effect on specific gravity readings. The radiator bulb hydrometer did not accurately predict colostral immunoglobulin.
    No preview · Article · May 1997
  • [Show abstract] [Hide abstract] ABSTRACT: The pasture, as compared to stall confinement, has been considered a more desirable environment for maintaining the health of the respiratory system in the horse. This conclusion is based on reports which showed that ventilation in most barns was generally poor, and that horses bedded on straw and fed hay were exposed to many forms of respirable debris. In this study, six normal horses were evaluated for evidence of airway mucosal inflammation after being housed on pasture or stabled in a barn for one month. The response of the horses' airways was measured by assigning scores for the degree of tracheal mucosal secretions that were observed by endoscopic visualization. Cytological examination of transtracheal wash secretions was also performed, as well as histologic evaluation of tracheobronchial tissues obtained by a transendoscopic epithelial biopsy technique. Samples were collected at three time points; the initial collection occurred after the horses were housed on pasture for one month. The horses were subsequently moved to a barn for an equal length of time and samples were obtained at the end of this period. The horses were then returned to their original pasture and final sampling was performed after they were housed in this environment for two months. There were no significant changes in any of the parameters evaluated, regardless of the environment in which the horses were maintained. These findings indicate that housing horses in a barn for four weeks does not cause tracheobronchial mucosal inflammation in a manner that could be detected using the methods employed in this study.
    No preview · Article · Nov 1996 · Journal of Equine Veterinary Science
  • [Show abstract] [Hide abstract] ABSTRACT: Transtracheal wash and bronchoalveolar lavage are diagnostic techniques that have been adopted from human medicine for monitoring inflammatory changes in the airway of the horse. Transendoscopic biopsy has also proven to be a valuable tool for obtaining samples of the airway mucosa in human patients. A transendoscopic technique was developed in this study for obtaining a respiratory mucosal biopsy from standing, sedated horses. Six normal adult horses were sampled at eight-week intervals for a total of three sample periods. Horses were monitored for adverse effects of the technique and none were noted. Sample sites were completely healed after eight weeks with no gross or histologic abnormalities. Biopsy samples were 3 to 4 millimeters in diameter, and 17 of 18 samples provided interpretable histological sections. Methods for handling, staining and evaluating tissue were also developed. The results of this study demonstrated that airway mucosal biopsy is a safe, repeatable technique that can be performed in the sedated, standing horse.
    No preview · Article · Sep 1996 · Journal of Equine Veterinary Science
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    [Show abstract] [Hide abstract] ABSTRACT: Changes in serum concentrations of Ca and parathyroid hormone (PTH) may develop in periparturient mares, may be influenced by dietary Ca, and may be associated with changes in Ca concentration of mammary secretion. Milk and blood samples were taken from eight mares on Farm A and eight on Farm B for 10 d before parturition and from four mares on each farm for 5 d postpartum. Milk Ca was measured by two commercial tests. Serum samples were analyzed for PTH and total Ca in 16 mares and for ionized Ca in six (Farm A). Parturition was induced in eight mares on Farm A and four on Farm B; no significant difference in serum Ca or PTH was found between mares with induced and spontaneous foaling. Mean serum total Ca decreased from 12.5 mg/dL to a nadir of 11 mg/dL on d 2 postpartum, and mean PTH increased from 46 pg/mL to a peak of 186 pg/mL on d 2 postpartum. Serum total Ca concentrations were lower and serum PTH concentrations were higher in Farm A mares than in Farm B mares, probably reflecting dietary Ca (.35% of DM on Farm A and .55% on Farm B). The serum PTH peak and Ca nadir occurred on d 2 postpartum, 1 d later than reported previously in dairy cows. Milk Ca concentration increased progressively from 7 d before parturition; this increase preceded, so was not dependent on, prepartal changes in serum Ca and PTH.
    Preview · Article · May 1996 · Journal of Animal Science
  • [Show abstract] [Hide abstract] ABSTRACT: A colorimetric test kit marketed for water quality analysis was used to measure calcium carbonate changes in diluted prefoaling mammary secretions. Daily samples (1 to 3 ml/day) were obtained from 59 Thoroughbred and Warmblood mares starting 14 days prior to foaling to the day of parturition. The sensitivity, specificity, and positive and negative predictive values of the test were calculated on the data collected from 56 mares and 377 prefoaling mammary secretion samples. The results indicate that this test is both sensitive and specific. The predictive value of a positive test (PVPT; positive test defined as the first occurrence that prefoaling mammary secretion calcium carbonate >/= 200 ppm) indicated that 51.4% of late term pregnant mares would foal within the ensuing 24-hour period, 84.1% within 48 hours and 97.2% within 72 hours. The predictive value of a negative test (PVNT; negative test defined as prefoaling mammary secretion calcium carbonate < 200 ppm) indicated that 99.6% of late term pregnant mares would not be expected to foal within the ensuing 24 hour period, % within 48 hours and 81.8% within 72 hours. This test is helpful as a prognostic tool in indicating the mare's approaching readiness for birth. It is also an accurate prognostic tool to predict that the mare is not likely to foal within 24h when calcium carbonate < 200 ppm in the diluted prefoaling mammary secretion.
    No preview · Article · Jul 1993 · Theriogenology
  • [Show abstract] [Hide abstract] ABSTRACT: Purebred Suffolk, Hampshire and Dorset lamb and yearling rams (n=753), underwent performance testing from 1986 to 1989. Scrotal circumference, birth date and entry weight were recorded for each ram entering the test station. Mean age in days at entry, weight (lbs), and scrotal circumference (SC; cm) were greatest for the Hampshire rams. For all rams combined (Dorset, Hampshire and Suffolk), the mean SC by month of age revealed rapid growth from 2 to 6 mo, with a 3- to 6-mo mean SC significantly (P</=0.05) larger than the mean SC for the previous month. From 6 to 12 mo there was no difference (P>0.05) for mean SC measurement and a less rapid increase in SC diameter. Between 12 and 13 mo a significant increase (P</=0.05) was noted in the mean SC measure. Hampshire rams had a significantly larger SC (P</=0.05) than Dorset rams at 3 mo and at 10 to 12 mo of age; Suffolk rams had a larger SC (P</=0.05) than Dorset rams at 9 to 12 mo. The mean SC for Hampshire and Suffolk rams differed only at 3 mo of age (P</=0.05). Simple regression analysis for SC vs log of age in days described the best fit of the data for predicting SC. For all breeds combined, the polynomial relationship was SC(cm) = -143.05 + 137.71log(age) - 27.073[log(age)](2). Most of the variability (r(2) = 0.738) in SC measurement in younger (2 to 12 mo) purebred Dorset, Hampshire and Suffolk rams was attributable to age of the ram in days. The currently recommended point-score system for evaluating ram breeding soundness could lead to discounting younger rams that have the potential to be satisfactory sires but that do not score high enough due to the influence of age vs SC development. In selecting sires, breed differences must be taken into consideration since the SC of Hampshire rams was different from that of Dorset and Suffolk rams at 3 mo of age and from Dorset rams at 10 to 12 mo of age.
    No preview · Article · Nov 1990 · Theriogenology