W B Ley

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

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Publications (25)29.36 Total impact

  • Equine Veterinary Education. 01/2010; 13(6):324 - 329.
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    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.
    Theriogenology 02/2004; 61(2-3):381-91. · 1.85 Impact Factor
  • Journal of Equine Veterinary Science 05/2003; 23(5):220-224. · 0.89 Impact Factor
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    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.
    Veterinary Parasitology 03/2001; 95(2-4):187-95. · 2.55 Impact Factor
  • Journal of the American Veterinary Medical Association 03/2000; 216(6):833-5. · 1.67 Impact Factor
  • Journal of the American Veterinary Medical Association 03/2000; · 1.67 Impact Factor
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    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.
    Journal of Andrology 01/2000; 21(1):45-52. · 1.69 Impact Factor
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  • Wynne A. DiGrassie, William B. Ley
    Journal of Equine Veterinary Science 10/1997; 17(10):528–529. · 0.62 Impact Factor
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    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.
    Journal of Equine Veterinary Science 11/1996; · 0.89 Impact Factor
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    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.
    Journal of Equine Veterinary Science 09/1996; · 0.89 Impact Factor
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    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.
    Theriogenology 07/1993; 40(1):189-98. · 1.85 Impact Factor
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    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.
    Theriogenology 11/1990; 34(5):913-25. · 1.85 Impact Factor
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    ABSTRACT: Performance tests were conducted on 583 purebred Dorset, Hampshire and Suffolk yearling rams at the Virginia Ram Test Station from 1986 to 1989. Birth dates at entry and weights (lbs) at entry and end-of-test were recorded for each ram. Entry and exit scrotal circumference (SC; cm) data were recorded for each year of the study. Breeding soundness examination (BSE) data at entry were obtained for only the last two years (1988-1989). The BSE followed the basic format recommended by the Society for Theriogenology. The number of seminal white blood cells per (100x) microscope field (WBC/LPF) were also recorded for each ram's ejaculate. Classification of rams into breeding groups (satisfactory, questionable and unsatisfactory) were made using a point-scale system based upon values obtained from SC, sperm motility and morphology assessments. Between-breed differences were noted for age at entry to the test station, weight per day of age, final weight at the end of the test period and average daily gain. Suffolk rams were younger in age (P</=0.01) than Dorset and Hampshire rams, but grew faster and heavier (P</=0.01). Between-breed differences were also noted for values within the point-score BSE system: Dorset ram sperm motility (P<0.05) and morphology scores (P<0.01) were higher than those for Suffolk rams. The number of Dorset, Hampshire and Suffolk rams classified as satisfactory, questionable or unsatisfactory potential breeders by the BSE method did not differ (P>0.05). Overall the percentage of rams classified as unsatisfactory, questionable and satisfactory was 11.8, 16.5 and 71.7, respectively. Rams with more than 10 WBC/LPF had significantly smaller SC at entry (P<0.01) than rams with less than 10 WBC/LPF. Most of the differences (75%) in BSE scores in this study were contributed by differences in semen quality (spermatozoal motility and morphology) not by differences in SC.
    Theriogenology 10/1990; 34(4):721-33. · 1.85 Impact Factor
  • Theriogenology 06/1990; 33(6):1177-1189. · 1.85 Impact Factor
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    ABSTRACT: Twenty-four Thoroughbred mares with breeding histories of having been barren for at least the previous 12 months were evaluated in a double-blind feeding trial to determine the effects of chelated mineral supplementation upon subsequent breeding performance. At the start of the trial (Day 0), mares were split into three dietary treatment groups of eight mares each and fed: (a) control diet with macro- and microminerals fed at NRC recommended levels for maintenance of the mature horse, (b) chelated minerals supplementation and (c) inorganic minerals supplementation at levels equal to Group B. Sixty days after initiation of the trial, there were no differences (P>0.05) between age, endometrial biopsy classification, calculated body weight and body condition score for mares between dietary treatment groups. A breeding performance trial was initiated at this time (Day 60). The number of first cycle and cumulative (i.e. over 3 estrous cycles) conceptions, number of first cycle and cumulative pregnancies and the number of total embryonic losses were not different (P>0.05) between the control and either the chelated mineral or the inorganic mineral groups. There were no harmful effects observed from feeding the chelated minerals 60 days prior to, and during, this breeding trial.
    Journal of Equine Veterinary Science 05/1990; · 0.89 Impact Factor
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    ABSTRACT: The effects upon equine endometrial histological features produced by 10 to 30% concentrations of dimethyl sulfoxide (DMSO) in sterile saline were compared with the effects of sterile saline (0.9% NaCl) alone as an intrauterine infusion therapy in 16 barren mares. No harmful histological changes were noted (P>0.05) as a result of the therapy. Thirty percent intrauterine DMSO therapy produced a significant (P<0.01) improvement (i.e., reduction of chronic inflammatory cell infiltrates and reduction of periglandular fibrosis) in endometrial biopsy classification in 18 of the 27 barren mares evaluated; whereas only 2 of 18 barren mares improved following intrauterine saline treatment in the control group. In subsequent breeding trials, the pregnancy rates following intrauterine therapy were no different between DMSO-treated mares and saline-treated control mares (P>0.05); however, there was a trend toward a higher pregnancy rate following DMSO therapy. The inability to control for sire variability in the breeding trials may have contributed toward the result that no significant difference could be demonstrated in the pregnancy rates between treated and control mares.
    Theriogenology 08/1989; 32(2):263-76. · 1.85 Impact Factor
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    ABSTRACT: A computer spreadsheet was developed to predict the economic impact of a management decision to use B-mode ultrasonographic ovine pregnancy diagnosis. The spreadsheet design and spreadsheet cell formulas are provided. The program used the partial farm budget technique to calculate net return (NR) or cash flow changes that resulted from the decision to use ultrasonography. Using the program, either simple pregnancy diagnosis or pregnancy diagnosis with the ability to determine singleton or multiple pregnancies may be compared with no flock ultrasonographic pregnancy diagnosis. A wide range of user-selected regional variables are used to calculate the cash flow changes associated with the ultrasonography decisions. A variable may be altered through a range of values to conduct a sensitivity analysis of predicted NR. Example sensitivity analyses are included for flock conception rate, veterinary ultrasound fee, and the price of corn. Variables that influence the number of cull animals and the cost of ultrasonography have the greatest impact on predicted NR. Because the determination of singleton or multiple pregnancies is more time consuming, its economic practicality in comparison with simple pregnancy diagnosis is questionable. The value of feed saved by identifying and separately feeding ewes with singleton pregnancies is not offset by the increased ultrasonography cost.
    Journal of the American Veterinary Medical Association 08/1989; 195(2):199-204. · 1.67 Impact Factor
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    ABSTRACT: Equine postpartum uterine bacterial contamination was studied. Thirteen mares were examined at foaling, at foal heat and again at the second estrus if not bred at foal heat (n=7). Twenty-three percent (3/13) of the mares showed no uterine bacterial contamination immediately post partum. This was increased to 77% (10/13) by foal heat and 100% (7/7) by the second post-partum estrus. Few anaerobic bacteria were isolated and were quickly eliminated. Anerobic bacteria do not appear to be a problem in the postpartum mare. The mare is capable of quickly eliminating postpartum uterine bacterial contamination. Endometrial etiology was shown to be a good screening test for uterine bacterial contamination in the postpartum mare. Bacterial endometritis has long been recognized as a major cause of infertility in the mare.5,8,12 Bacterial culture techniques over the years have been improved as have the interpretation of such results. It is generally agreed upon that the isolation of bacteria by itself is insufficient evidence of disease.3,16,17,19,25 Certain bacteria, Streptococcus zooepidemicus, Escherichia coli, Pseudomonas aeruginosa and Klebsiella pneumonia, are known to be the major bacterial pathogens responsible for most of the cases of endometritis.7,18,26 Isolation of bacteria in pure culture also is considered to be clinically significant; mixed cultures probably indicate insignificant contamination.2,21 The clinician also must consider the quantity of organisms isolated.1,3,7,19,26 Most pathogens occur in large numbers with heavy growth noted when cultured. In addition to kinds and quantity of bacteria isolated from the uterus, there also must be evidence of inflammation detected by physical examination of the genitalia, endometrial cytology and/or endometrial biopsy.4,9,14,15,25,27,28 The presence and significance of anaerobic bacteria in the mare's uterus has not been throughly addressed. It has been documented that aerobic and anaerobic bacteria play a significant role in postpartum uterine infections in the cow.20Fusobacterium necrophorum and Corynebacterium pyogenes apparently have a synergistic effect to increase the severity of postpartum uterine infections in the cow.20,23 Anerobic bacteria, as well as mycoplasmas and viruses, have been suggested as possible causes of endometritis in the mare when evidence of inflammation is present but no aerobic bacteria are isolated.7,14,21,27 The purpose of this study was to document aerobic and anaerobic bacterial contamination of the uterus in the postpartum mare. Endometrial cytology was investigated to determine if there was a relationship between the presence of bacteria in the postpartum uterus and an inflammatory response.
    Journal of Equine Veterinary Science 05/1989; 9(3):141-144. · 0.89 Impact Factor
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    ABSTRACT: The effects of oxytocin and two prostaglandin (PG) F(2)alpha analogues, prostalene and alfaprostol, on uterine pressure in the mare were measured using balloon-tipped catheters connected to pressure transducers. The PGF(2)alpha analogues caused increased uterine pressure beginning 7 to 15 min postinjection and persisting for the duration of each 60 min recording session. Forty postpartum mares of light-horse breed were used to evaluate the effects of prostalene on postpartum pregnancy rate. Eighteen mares were injected by aseptic technique subcutaneously with 1 mg prostalene twice daily, beginning on the day of foaling (Day 0) and continuing for 10 consecutive days (Day 10) or until the mare was first bred at foal heat. Twenty-two postpartum mares were injected with 1.0 ml sterile saline by the same technique as the controls. Of treated mares, 76.9% were diagnosed pregnant after breeding versus 44.4% of the control mares (P = 0.07). Of treated mares, 66.7% bred at their second postpartum estrus became pregnant versus 28.6% of control mares (P = 0.03). Prostalene, given at 1 mg twice daily for 10 d postpartum, produced an increased pregnancy rate after both foal heat and second postpartum estrus breedings in the mare.
    Theriogenology 02/1988; 29(5):1113-21. · 1.85 Impact Factor