FALL BROODMARE EXAMS Patrick M. McCue DVM, PhD ...

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FALL BROODMARE EXAMS Patrick M. McCue DVM, PhD ...

FALL BROODMARE EXAMSPatrick M. McCueDVM, PhD, Diplomate American College of TheriogenologistsThe breeding season is over with on mostQuarter Horse farms by the middle of thesummer and is completely finished bySeptember. It is understandable that manyowners and breeders want to take a breakfrom broodmare work when the season isover. However, mares should not becompletely ignored during the late summerand fall months.It is common practice to examine maresinitially 14 to 16 days after breeding for anearly pregnancy diagnosis and then reexaminemares periodically until they are 50to 60 days in foal. These examinations inearly pregnancy are prudent because mostcases of pregnancy loss occur in the first 60days of gestation.A follow-up examination in the late summeror early fall, at approximately 5 months ofgestation, is recommended to determine ifmares are still in foal or if the pregnancy hasbeen lost. Mares previously determined tobe pregnant that are found to be open on the5 month recheck can be examined further todetermine if a cause for the pregnancy losscan be identified. The examination mayinclude a review of the breeding history, athorough physical evaluation, palpation andultrasound examination of the entirereproductive tract, speculum examination ofthe vaginal vault and cervix, collection ofculture and cytology specimens from theuterus and possibly a uterine biopsy. Thegoal is to identify reproductive problemsthat may be associated with reduced fertilityor a decreased ability to carry a foal to termand correct the issue as soon as possible andnot wait until the next breeding season. Forexample, if a uterine infection is detected,prompt treatment should be initiated whichmay include uterine lavage, oxytocinadministration, infusion of antibiotics intothe uterus, and possibly a Caslick'sprocedure to reduce the risk ofrecontamination in mares with poor perinealconformation.Pregnant mares should be housed separatelyfrom other horses on the farm, includingnon-pregnant mares, geldings andshow/performance horses, to limit thepotential for exposure to infectious diseasesthat may cause abortion. The infectiousagent that has the highest risk for causingabortion in mares is equine herpesvirus type1 (EHV-1) also known as rhinopneumonitis.There are two killed-virus vaccines availablecommercially approved for use in healthymares as an aid in the prevention of abortiondue to EHV-1. These are Pneumabort-K ® ,produced by Fort Dodge Animal Health, andProdigy ® , produced by Intervet, Inc.Pregnant mares are at greatest risk ofabortion if exposed to EHV-1 in the secondhalf of gestation. As a consequence, it isrecommended that pregnant mares be1


vaccinated against EHV-1 at 5, 7 and 9months of gestation.Mares that are determined to be open in thelate summer/fall examination can be housedunder lights beginning in December tostimulate early follicular development andadvance the date of the first ovulation of theyear. Mares maintained under natural lightconditions in geographical areas wheredistinct seasonal climate changes exist stopcycling during the winter months. The firstovulation of the year will occur in thesemares, on average, in late April or early May.Open mares exposed to 15 or 16 hours oflight and allowed 8 to 9 hours of darknessbeginning in early December will startcycling in early to mid February. Mares canbe housed outside during the day andbrought into a barn or paddock in the lateafternoon. Automatic timers are an efficientand effective way to control the duration oflight exposure. The timers can be set to goon an hour before dusk and shut off at 10:00or 11:00 at night.On many farms, the pregnancy status ofmares is not rechecked between the 50 daypregnancy examination and the followingspring. Even then, a mare may not beevaluated unless it is felt that she is not asbig as she should be or is not bagging up. Itis a fact of life that some mares are notgoing to carry their foal to term. It will betoo late to use lights to stimulate an earlyonset of cyclicity in an open mare if thepregnancy status is not determined until thespring.Confirmation of pregnancy status in the fallwill allow for the early identification ofopen mares and give owners an opportunityto make appropriate management decisionsfor each mare.2

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