Respiratory Problems

most regions. Within the host, consecutive stages (early L3, late L3, developing L4) of cyathostome larvae reside within fibrous "cysts" in the mucosa of the cecum and colon. The EL3 stage larvae may arrest development, thereby allowing worms to persist for up to 2.5 years after infection. LL3 and DL4 mature progressively and emerge from the cyst to become adult worms. The prepatent period of cyathostomes infection is 6 weeks in helminthnaive foals, but >14 weeks in sensitized, mature horses. The major damage from cyathostome infection occurs when larvae emerge from tissue cysts, but clinical disease is also associated with larval invasion of the mucosa. The objective of controlling cyathostome infections is prevention of environmental contamination with strongyle eggs~ This can be accomplished by anthelmintic treatments repeated at prescribed intervals. The frequency of anthelmintics treatment can be predicted by the egg reappearance period (ERP), which is the interval from treatment to resumption of egg shedding in feces. The duration of the ERP is approximately 4 weeks after administration of piperazine, pyrantel pamoate, or b e n z i m i d a z o t e s , 6 to 8 w e e k s after ivermectin, and approximately 12 weeks after moxidectin. Comprehensive, strategic programs that utilize this ERP are described.

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EFFECT OF OXIDATIVE STRESS ON EQUINE S P E R M A T O Z O A Ball BA, Baumber J, Gravance CG, Vo A Department of Population Health and Reproduction, University of California, Davis, CA 95616, USA

Oxidative stress has been identified as an important factor in male infertility in a number of species. This study examined the ability of equine sperm to produce reactive oxygen species (ROS), the effect of ROS on equine sperm function, as well as the major scavenger systems for removal of ROS. Sperm damaged by freezing and thawing produced significantly (P < 0.05) more HzO 2 than live sperm. Generation of ROS by a xanthine-xanthine oxidase system (XXO) significantly depressed sperm motility without affecting the percentage of viable sperm. Of the ROS scavengers (catalase, superoxide dismutase and glutathione), only catalase was able to prevent the decline in sperm motility produced by X-XO. The activity of catalase in equine seminal plasma was determined in ejaculates from 20 stallions. Evaluation ofcatalase activity from accessory sex glands of 3 stallions indicated that most of the activity was derived from prostatic secretions. This study indicates that HzO 2 is the primary ROS associated with damage to equine sperm and that catalase is the most effective scavenger associated with protection against loss of sperm function. Fortunately, the activity ofcatalase in equine seminal plasma was found to be extremely high. Procedures, such as cryopreservation, that remove seminal plasma and damage sperm increase the likelihood of impaired sperm function due to ROS.

to test the efficacy of a LHRH-analog (busereline) for hastening ovulation in mares. Four cross over trials were performed to compare, in each experiment, two treatments, alternatively injected to induce ovulation of 2 or 4 successive estrous cycles of embryo-donor mares. Tested treatments started when a growing follicle reached 33 mmin diameter. Variousregimines of injections in the study are described using busereline at 40gg and 20~g, hCG and a placebo. These data show the efficacy of busereline (20gg) injected 4 times every 12 hours to induce ovulation in mares. This treatment is a useful alternative to hCG when mares are immunized from hCG.

WHEN DO HORSE EMBRYOS ENTER THE UTERUS? PRACTICAL APPLICATIONS IN EMBRYO TRANSFER Bruyas JF, Colchen S, Granchamp de Raux

A, Nicais J-L, Battut I, Fieni F, Tainturier D Nantes Veterinary School, France

The aim of this study was to evaluate the exact age when the equine embryo reaches the uterus. In donor mares, after inductions of ovulation, the time of ovulation was determined by hourly ultrasound examinations. In the first experiment, 60 nonsurgical embryo collections were performed 144 + 0.5 (Day 6), 156 + 0.5 (Day 6.5) or 168 + 0.5 h (Day 7) after ovulation. In experiment 2, 45 nonsurgical embryo collections were performed 144 + 0.5 (Day 6), 147_+0.5 (Day6.125) or 1 5 0 + 0 . 5 h (Day6.25) after ovulation. In experiment 1, the recovery rate at D6 (0/20) was significantly lower (0.001) than the recovery ratesatD6.5(9/17;53 %)andDT(12/23; 52 %). In experiment 2, the recovery rates were not different: 2/16 (12 %) at D6, 3/14 (21%) at D6.125 et 5/15 (33 %) at D6.25. Variabilities were observed in development stage and size among embryos collected at the same age. These results suggest that; (i) horse embryos don't enter the uterus at the same age but (ii) all of them are in the uterus USE OF BUSERELINE TO INDUCE at 156 h (D6.5) after ovulation and (iii) OVULATION IN CYCLIC MARES Bruyas JF, 1Trocherie E, 1Hecht S, 1Lepoutre embryonic development rates may differ N, 1 Granchamp de Raux A, ~ Nicais 3-L, 1 a m o n g embryos. This study explains why Battut I, 1 Fieni F, 1 Hoier R, 2 Ergron L, s in practice, when ovulations are checked only once a day, recovery rates of embryos Tainturier D ~ 1 Nantes Veterinary School France; 2 Royal are lower at Day 6 than at Day 7. Embryo Veterinary and Agricultural University, Den- collections would be performed after Day 6.5 post-ovulation. (P) mark; 3 Hoechst-Roussel Vet, France Owing to possible immunization of PLASMA P R O G E S T E R O N E mares against human Chorionic GonadotC O N C E N T R A T I O N S AND EARLY ropin (hCG) it would be useful to have DEVELOPMENT OF HORSE another way for induction of ovulation in EMBRYOS mares. The purpose of these 4 studies was

JOURNAL OF EQUINE VETERINARY SCIENCE

Colchen S, Battut 1, Fieni F, Siliart B, Tainturier D, and Bruyas JF Nantes Veterinary School, France The aim of this study was to evaluate relationships between plasma progesterone (P4) concentrations and development rate of embryos. In donor mares, after inductions of ovulation, the time of ovulation was determined by hourly ultrasound examinations. Blood samples were taken daily from the time of ovulation (Day 0) fill nonsurgical embryo collection performed 156 h (Day 6.5) or 168 h (Day 7) after ovulation, for measurement of P4. In all mares, increasing in plasma P4 levels was significant from the second day after ovulation. Plasma P4 concentrations were not different between groups of mares with or without embryo. There was no significant correlations between plasma P4 concentrations (at the moment of embryo collection and area under the curve) and size, development stage, and number of cells of embryos. In contrast with a previous study (Boyle et al., 1989, Equine Vet J., suppl,8, 10-13), our data show that a strict supervision of plasma P4 secretions gives no help in the management of embryo donor mares.

CURRENT METHODS FOR INDUCTION OF THE ESTROUS CYCLE IN THE ANESTROUS MARE Daels P. Abstract not available.

THE KEY TO MORE EFFICIENT EMBRYO TRANSFER IN HORSES: SUPEROVULATION OR FREEZING EMBRYOS Daels P. Abstract not available.

FUNCTIONAL CORRELATIONS OF FROZEN EQUINE SPERM WITH SUPEROXIDEDISMUTASE ACTIVITY Ducci M, Tedeschi D, Villani C, Gazzano A, Sighieri C, Martelli F Anatomia Biochimica e Fisiologia Veterinaria Universit~ di PisaViale delle Piagge n. 256124 Pisa, Italy Frozen equine semen quality is estimated using parameters as motility percent and sperms concentration. The freezingthawing process induces damages to spermarie the membrane, wi}h subsequent loss of motility. Cryopreservation causes an increase of membrane permeability and enhances lipid peroxidation. Equine spermatozoa, as human, are sensitive to the peroxidative injuries due to high levels of

Volume 19, Number 9, 1999

reactive oxygen species. Superoxidedismutase plays an important role in cell protection from superoxide anion damages. The aim of this research was to investigate superoxidedismutase activity on frozen equine spermatozoa in order to correlate sperm functional and biochemical parameters. Twenty cryopreserved paillettes of equine semen were used for this study. HOS-test (membrane functional integrity test), cell count and motility evaluation were carried out after thawing. Intranemaspermic superoxidedismutase activity was determined by the inhibition of nitroblue tetrazolium reduction. Moreover intranemaspermic total proteins content and alkaline phospatase were assayed.A significant linear correlation was observed between supcroxidedismutase activity and motility (r=0.914, p<0.00l), and HOS-test (r=0.569, p<0.02). Fall in superoxidedismutase activity observed in samples with lower motility could be attribute to enzyme loss or to its reduced activity. This last hypothesis could explain the correlation of superoxidedismutase activity with the parameters considered. In fact no correlations were found between intranemaspermic alkaline phosphatase and totaI protein content with motility and HOS-test, excluding the first hypothesis. The peroxidative process involves structural, functional and biochemical alterations of sperm and enhances the irreversible motility reduction. (P)

tested with Spearman non-parametric test. Whatever protocoI or cryoprotectant was used, horse embryos with thick capsule were more damaged after freezing than those with a thinner capsule. For glycerol treated embryos correlation was statistically highly significant (p<0,001). Dimethylsulfoxide and propanediol groups are too small to be tested. In accordance with the hypothesis put forward by others, our data showed, for the first time, that the thickness of the capsule would be the major parameter of a successful deep-freezing. The capsule would impede osmotic flux between embryos and medium, to such a degree, when capsule was very thick, that cryoprotectant could not have sufficient efficacy. Further experiments would have to focus on this point. (P)

UTERINE MYOELECTRICAL ACTIVITY IN THE LATE GESTATIONAL MARE: WORK IN PROGRESS

LeBlanc M, Lester G, Thomas M, Mayne M Department of Large Animal Clinical Sciences, College of Veterinary Medicine, University of Florida, Gainesville, FL 32610USA It is crucial that we understand the relationship between endocrinology and uterine myoelectrical activity patterns in late gestation if we are to develop rational treatment protocols to prevent premature labor from placentitis. Our goals in this CAN HORSE EMBRYOS preliminary study were to 1) develop a BE FROZEN? technique to measure uterine myoelectrical THE EMBRYONIC CAPSULE activity in late gestation and 2) characterize INFLUENCE the myometrial activity pattern in the mare. Legrand E,1 Battut 1,2 Tainturier D, 2 Bruyas We hypothesized that the pattern of uterine JP myoelectrical activity late in gestation is 1Military Riding Center, 77307 similar in the mare and primate. Five pregFontainebleau, FRANCE, 2Veterinary School nant pony mares were instrumented with of Nantes, 44307 Nantes, France myometrial electrodes between days 270Since 1982 success rates of equine 288 of gestation. Myometrial electrical embryos freezing have not increased. The activity was measured in 2 to 4 hr windows l i m i t i n g factor of horse e m b r y o s ' spaced through the 24 hr day for a total of freezability has not been found. The aim of 11 hr daily beginning on day 305 of gestathis study was to evaluate relationships tion. Repeated measures analysis (Mixed between cellular damage and thickness of 9Procedure, SAS Institute) was performed the embryonic capsule in frozen embryos. on the myoelectrical dependent variables. Histological sections of 5 previous studies All mares foaled without complication bewere used. In each study, embryos were tween 322 and 333 days of gestation. All frozen and thawed with conventional pro- foals stood and sucked within 60 rain of cess, then they were cultured for 6 hours, birth9 Myoelectrical activity of mares had fixed and stained with blue toluidine. In similarities to the primate, in that the inaddition to the necrotic nucleus count, the crease in nightly activity was reversible thickness of the embryonic capsule was and progressive as the mare neared parturidetermined. This thickness was graded be- tion. Seven to 8 days prior toparturition the tween 0 and 4 (0 = absence, 4 = thick). frequency of myoelectric complexes began Correlation between these two factors was to increase during the evening and night

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uuucs ~atc m gc~tauun, lv.tyueiecmcal acuvity increased during the last week of gestation in the mare, in a pattern similar to the primate. The cause of this switch is not known.

A TEN-YEAR SURVEY OF CAUSES OF ABORTION AND NEONATAL DEATH IN BRITISH HORSES Smith KC, Blunden AS, Whitwell KE, Dunn KA, Wales AD Centre for Preventive Medicine, Animal Health Trust, Lanwades Park, Kentford, Newmarket, Suffolk CB8 7UU, UK The diagnoses in over 1,000 equine fetuses and neonatal foals submitted to a Newmarket diagnostic laboratory over a ten-year period from 1988 to 1997 were reviewed. The prevalence of different diagnoses varied with gestational age. Lethal vascular compromise associated with torsion of the umbilical cord was the most common diagnosis. A related disorder was ischemic necrosis of the cervical pole of the allantochorion, which was also associated with an overlong umbilical cord. There were some in which placental ischemia was diagnosed without a primary umbilical cord lesion. Other non-infective causes of abortion or neonatal death included twinning, intrapartum stillbirth related to dystocia or relative fetal oversize, and premature placental separation. The most common infective cause of abortion was placentitis. Most incidents were ascending bacterial or fungal i n f e c t i o n s , w i t h E. coli a n d S. zooepidemicus being the most c o m m o n bacteria isolated, although there was a small number of incidents of non-ascending placentitis. There were infections with EHV-1 or EHV-4. Miscellaneous causes of abortion, each accounting for less than 1% of the total incidents, included body pregnancy, fetal diarrhea syndrome and primary villous hypoplasia. No diagnosis was made in some, including early abortions, extensively scavenged fetuses and submissions lacking placentas.

BEHAVIORAL RESPONSE TO EARLY PRE-PUBERTAL CASTRATION Weeks dW, Caudie AB, CrowelI-Davis S, Heusner G Department of Psychology, Franklin College of Arts and Sciences; Department of Large Animal Medicine, College of Veterinary Medicine; Department of Anatomy and Radiology, College of Veterinary Medi-

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t~any prc-puDcrtal castration LLr~) potentially may provide a less stressful method of castration in the horse. Recovery time for EPCs may be shorter than that of yearling or older castrates. This study is the first in a series to assess the behavioral responses to and recovery from this type of castration. For each procedure, the castrate was paired with a control agemate. Each animal was then anesthetized, tied, and if a treatment animal, castrated. Control animals were subject to the same procedure less the actual castration. Each animal was observed for one hour immediate postcastration as well as one hour on the first day post-castration. A G L M procedure was run to assess any difference between the treatment groups as well as in the expression of these behaviors. No differences were found between castrates and controls in the percentage of the sample spent in the following behaviors: walking, grazing, nursing, lateral rest, and sternal rest. There was no difference in the recovery behavior of the EPCs and their agemates. Hence, the castrates suffered no adverse behavioral effects fiom the procedure. Further research wilt assess the behavioral differences in recovery between EPCs and yearling castrates. (P)

EQUINE NOCARDIOFORM PLACENTITIS Williams N, Donahue J, McDowell K, Bolin D, Giles R, Harrison L, Hong C, PattersonKane J, Poonacha K, Swerczek T. Tramontin R

Department of Veterinary Science, University of Kentucky, Lexington, KY 40546, USA Nocardioform placentitis, caused by unclassified gram-positive filamentous branching bacteria and having a unique pathological appearance, has increased dramatically in central Kentucky over the last two foaling seasons. This study was undert a k e n to c h a r a c t e r i z e a n d c o m p a r e nocardioform placentitis on pathological, epidemiological, and bacteriologicalbases. The source of material for this study was fetuses and placentas submitted to the University of Kentucky, Livestock Disease D i a g n o s t i c Center. A c o m p l e t e postmortem work-up was performed on each equine fetus and placenta submitted to the laboratory. Basic epidemiological inform a t i o n was o b t a i n e d o n t h e c a s e s . Nocardioform placentitis was the most common type of placentitis diagnosed over the

slve, area oi placens locatea in me region where the horns join the body of the placenta. The area of placentitis was typically covered by thick, tenacious, mucoid exudate. The underlying allantochorion appeared thin as a result of destruction of the chorionic villi. Microscopically, the chorionic surface was covered by amorphous material with enmeshed filamentous bacteria. There was necrosis of the chorionic villi with infiltration by leukocytes. Bacteriological findings indicate that the causative bacteria represent a heterogeneous, but similar, group of organisms with antimicrobial sensitivity patterns that allow for grouping of isolates.

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