Ca.uky.edu/equine Thehorse June 2018
ca.uky.edu/equine TheHorse.com JUNE 2018B R O U G H T TO Y O U B Yistock.comIt’s All in the Genes:Horse Traits and HeritabilityChestnut horses mightbe genetically wired tobe more sensitive toenvironmental stimuli.What are you drawn to in a horse? A flashy coat color? A puppy dog personality? Smooth-as-molasses gaits? Well,your dream horse didn’t come by these traits by happenstance. Many characteristics such as coat color, height, athleticability, and behavioral tendencies are genetic in nature. And researchers are using “genomics,” the study of gene heritability,structure, and function, to determine which characteristics areconnected to which genes.First, let’s break down the terminology. The genome includes all DNA thatgoes into an individual from spermpairing with an egg. Every cell contains DNA in the form of chromosomepairs—except for gametes, or sex cells,which just have one chromosome.Each strand of chromosomal DNAis made up of organic moleculescalled nucleotides (guanine, cytosine,adenine, and thymine). Their sequenceleads to differences in the traits the individual displays, such as coat colors.Differences in the genomic DNAsequence between individual horsesare called single nucleotide polymorphisms (SNPs, or “snips”). If SNPsare located near each other on a1c hromosome, they will likely be inherited together; this proximity enablesresearchers to investigate specificregions of the genome that vary infrequency between horses.Samantha Brooks, PhD, assistantprofessor and founder of the University of Florida’s Brooks Equine GeneticsLab, in Gainesville, says SNPs aren’tthe only reason for genome variation.Much of it is also due to sequencerearrangements or changes. “Genesthat have flipped or duplicated may beresponsible for variation in phenotype(observable characteristics),” she says.For instance, a sequence change isresponsible for tobiano color (whitehair on a base coat color) in pintohorses, says Brooks, who earned herdoctoral degree from the University ofKentucky (UK) Department of Veterinary Science. While most rearrangements are benign, some are fatal, suchas the overo lethal white gene responsible for a disease that suppressesintestinal activity.Let’s look at some of the harmless (and even desirable!) geneticvariations that create horses’ unique characteristics.Coat Color’s Link to BehaviorYou’ve probably heard peopledescribe chestnuts, or “redheads” asthey’re fondly called, as excitable andreactive. It turns out there might besome biological truth to this stereotype, says Brooks. In one study inIn This IssuePost-Mortem Exams forRacehorses 4Cutaneous Lymphangitis 6Potomac Horse Fever inKentucky Horses 7
Bluegrass Equine Digest ca.uky.edu/equine TheHorse.com June 2018It’s All in the Genesments than bay horses. This particularmutation might also keep the adrenalgland from releasing natural steroidhormones in response to stress, therebyleading to a calmer temperament.Courtesy Dr. Samantha Brookshumans, researchers compared painresponses in redheads to those ofnonredheads. Subjects rated their painin response to small electric shocksSpooking and the Startle Responsefrom electrodes attached to their shins.You’ve always known your spookyThe researchers then administered angelding is a bit of a scaredy-cat, but didanalgesic and asked the participants toyou know he might be genetically wiredrerate the pain. The redheads consisto react to things the way he does? Unitently perceived the electrical shocks asversity of Florida researchers recentlymore painful than nonredheads did, butstudied Quarter Horse weanlings tothey reported relief from analgesia.map the genes for spooking behavior.It turns out that both people and“The initiation of a spook begins withhorses have mutations in the MC1Ra startle response, which is a neurologic(melanocortin receptor 1) gene. Thisreflex, not a conscious effort,” Brooksgene is responsible for signaling cellssays. “Some genetic changes result incalled melanocytes to producethe pigment melanin and establish base coat color. Redheads(both human and horse) have avariant of this gene that prevents them from producing theblack pigment and allows themto produce only red pigments. Inhumans the MC1R loss-of-function mutation results in red hair,along with increased sensitivity to the sun and a lower paintolerance. In horses, a similarmutation produces a chestnutcoat color.Researchers are comparing weanlings’ genetic makeup to“The melanocortin receptorstheir tendency to spook.in the brain are in part responsible for translating a signal from thatan alteration in the neurologic pathwayopioid class of chemicals (which thecontrolling the startle response.”brain produces and uses for signaling),All study horses received uniformand the same receptors on melanocytesenvironmental training (e.g., they wereare responsible for receiving signals forhalter-broke at the same time, etc.). Allwhen to turn black pigment on or off,”also experienced the same experimentalBrooks explains. “This mutation in bothsetup: Once the weanlings were acchestnut horses and redheaded womencustomed to being fed from a pan increates a defective receptor that doesn’ta round pen, a researcher would popreceive a signal for pigment controlopen a brightly colored umbrella nearbyor for pain relief.” This might make awhile they ate. The team catalogued thechestnut-coated horse more sensitive toresponses—ear flick, increased heartenvironmental stimuli.rate, defecation, distance traveled, andAnother base coat color gene,the likelihood and speed of return to theASIP (agouti-signaling protein), isfeed pan. Some weanlings continuedassociated with behavior in horses.eating, some refused to return to theThe ASIP gene works in the same sigfeed pan, and others exhibited behavnaling pathway to suppress the effect ofiors across the spectrum. The researchthe MC1R gene. Brooks and colleaguesers used a statistical model to scoresurveyed owners of 215 Tennesseeeach individual’s likelihood to startle.Walking Horses to compare 20 tem“To map something, you must firstperament traits with DNA informationbe able to precisely measure it,” saysextracted from the base of their hairBrooks. Now the researchers will invesfollicles. Horses with a loss-of-functiontigate each weanling’s genetic makeupmutation in ASIP, which results in aand look for genomic markers that corblack coat color, tended to have morerelate with its score.self-reliant and independent tempera“A practical objective of this work is2Masth ead University of Kentucky Ag EquineProgramsJenny Evans, MFA, co-managing editorand senior veterinary science marketingand promotion specialist,jenny.evans@uky.eduHolly Wiemers, MA, APR, co-managingeditor and communications director ofUK Ag Equine Programs,holly.wiemers@uky.edu Bluegrass Equine DigestAdvisory BoardBob Coleman, PhD, PAS, associate professorand extension horse specialistDavid Horohov, MS, PhD, chair of UK'sDepartment of Veterinary Scienceand director of the UK Gluck EquineResearch CenterMichael “Mick” Peterson, PhD, director ofUK Ag Equine Programs and professorin the department of biosystems andagricultural engineeringRay Smith, PhD, professor and forageextension specialist in the departmentof plant and soil sciencesJill Stowe, PhD, associate professor in thedepartment of agricultural economics Bluegrass Equine DigestEditorial CommitteeCraig Carter, DVM, PhD, Dipl. ACVPM,director and professor of the UKVeterinary Diagnostic LaboratoryLaurie Lawrence, PhD, professor inthe department of animal and foodsciencesKrista Lea, MS, coordinator of UK’s HorsePasture Evaluation Program in thedepartment of plant and soil sciencesMartin Nielsen, DVM, PhD, Dipl. EVPC,ACVM, associated professor at the UKGluck Equine Research Center The Horse: Your Guide ToEquine Health CareErica Larson, News EditorBrian Turner, Layout and DesignThe Bluegrass Equine Digest is a registered trademarkof the University of Kentucky Ag Equine Programsand Gluck Equine Research Center. The BluegrassEquine Digest is produced by the University ofKentucky in partnership with TheHorse.com andsponsor Zoetis. It is published monthly to provideup-to-date information on equine research fromthe University of Kentucky’s College of Agriculture,Food and Environment. Research material is meantto be shared. However, materials are copyrightedand require reprint permission from UK Ag EquinePrograms. Past issues of the Bluegrass Equine Digestare available at www2.ca.uky.edu/equine/bed.
Bluegrass Equine Digest ca.uky.edu/equine TheHorse.com June 2018to create a genetic test for the tendencyto spook, based on a population-wideaverage,” says Brooks. “Recreationalriders often want a quiet horse, whereasa show jumper may desire a horse withlightning-fast reflexes. A DNA samplesubmitted for genetic testing may helppeople decide if a young horse will beappropriate for their athletic endeavors.”Along similar lines, Ann Staiger, MS,PhD, a recent graduate of Brooks’ team,is conducting an ongoing experimentwith Tennessee Walking Horses to mapthe genetics responsible for tractabilityand for willingness to load on a trailer.Genes for SpeedHistorically, breeders have had to relyon conformation and progeny performance records to predict a physicaltrait’s heritability. Advances in technology and gene identification have led tothe availability of tests that help determine if the sire and/or dam has actuallypassed on specific genetic markers forperformance. With potentially betterodds of acquiring a highly talentedhorse, there has been much interest inidentifying genetic variables that impactracing performance.Ernest Bailey, PhD, professor atUK’s Maxwell H. Gluck Equine Research Center, in Lexington, is involvedwith The Horse Genome Project. Hesays several laboratories have investigated racing performance andthe MSTN (myostatin) gene. They haveidentified two alleles (different formsof a gene at one chromosome location)on the MSTN gene—the T-allele fordistance and the C-allele for sprinting.The T-variant is common in Arabianlines that produce successful endurancehorses. In contrast, Quarter Horseshave a high frequency of the C-allele forsprinting, whereas Thoroughbreds havea mix of the two.Researchers have found that myostatin mutations are associated withincreased muscling, distribution of fasttwitch muscle fibers, and hindquarterpower. Practically applied, looking atpedigrees of Thoroughbreds that excelas 2-year-olds in elite middle-distance(8- to 12-furlong, with a furlong being 1 8 mile) races, common sires include great 20th-century stallion Nearcoand his sons Nearctic, Nasrullah, andRoyal Charger. All these horses’ genesWiki Commons, Anne M. Eberhardt/The HorseIt’s All in the GenesNearco (left) is one of the common grandsires of elite racehorses, including Eclipse champion filly and2008 Kentucky Oaks winner Proud Spell. He and his descendants carry the C-allele of the myostatingene, which confers early muscling and speed.contain the C-allele of the myostatingene, which confers early muscling andspeed in 2-year-olds. The myostatingene profile can help predict an individual’s best distance, but researcherscaution not to consider it a speed geneor use it to define a horse’s racing class.The Genes Behind GaitingGaited horses rely on the “gait-keepermutation,” DMRT3 SER301STOP, tomaintain their gaiting at high speedwithout breaking into a canter. Horseswith this mutation tend to use intermediate (i.e., trotting or pacing) gaits morefrequently, says Brooks.“Racing performance and gait aremuch more complex than can be explained by a single gene, but this genehas a major impact on gait,” says Bailey.In a 2014 evaluation of breeds worldwide, Swedish researchers found thismutation in 68 of 141 breeds. It wasmost common among gaited breeds orharness racing horses and often absentin other breeds. Bailey says selectionfor it has enabled its spread in Standardbreds, Saddlebreds, Missouri FoxTrotters, Paso Finos, Icelandic horses,and Kentucky Mountain Saddle horses,to name a few.Height’s Link to “Roaring”Researchers have noted a positivecorrelation between Thoroughbredracehorse height (and leg length) withearnings. But breeding pressure toinstill the “tall” gene might have createdunintended consequences. Scientistshave now identified a link betweenheight and the respiratory conditionrecurrent laryngeal neuropathy (RLN,or “roaring”) in Thoroughbred racehorses and in draft horses. In a 2014study out of Michigan State University,3the authors demonstrated “a significantassociation of RLN with the LCORL/NCAPG locus (the position of a gene ona chromosome) on equine chromosome3 previously shown to affect body sizein horses.” This same location is knownto have a significant effect on Thoroughbred withers height.“Genes are strung along the chromosome like pearls on a necklace,” saysBrooks, reflecting on SNP proximity.“Those that are nearby to one anotherwill tend to stay together and aren’t often separated by the process of recombination,” which produces offspringwith combinations of traits differentfrom those found in either parent.“If selective breeding increases thefrequency of the tall gene, and if itsits on the same chromosome as theneuron-affecting gene, then there maybe a simultaneous increase in both frequency of height and for a disease likeroaring,” she says.More research is needed to determinethe RLN and height genes’ actual proximity or if they are the same gene performing two unique functions, says Brooks.Take-Home MessageGenomic science can help breedersdecipher a horse’s potential appearance and performance qualities. Theseare only a few of the current projectsgeneticists are working on involvingequine athletic ability, coat color, andbehavior.Similar work on other species lays afoundation to select and test for particular equine ability and behavior profilesthat best suit a rider’s pursuits. Nancy Loving, DVM, is a freelance writer forThe Horse and owns Loving Equine Clinic, inBoulder, Colorado.
Bluegrass Equine Digest ca.uky.edu/equine TheHorse.com June 2018istock.comRacehorse Breakdowns:The Importance of Post-Mortem Examsset of circumstances, the post-mortemexamination brings objectivity to theseobservations.The ultimate goal of any post-mortemprogram is to mitigate the horse’s injuryrisk and, in turn, the exercise riders andjockeys that are involved. Catastrophicbreakdowns are the leading cause ofserious injury to riders, and in sometragic cases, death. While post-mortemexaminations might be “too late” forthe horse in question, the value to theentire population of racehorses and tothe connections of a particular horseare invaluable. We owe it to the horses,riders, trainers, and the racing community as a whole to address this issue.Breakdowns are not inevitable events.We can mitigate the risk of their occurrence in racehorses through careful anddetermined study.CONTACT—Laura A. Kennedy, DVM, Dipl.ACVP—drlaurakennedy@uky.edu—859/257-More than 80% of horses that suffer a fatal musculoskeletal injury have pre-existing underlying pathology related to the fracture, indicating that the final catastrophic event is the culmination of repetitivewear and not an isolated incident caused by a “bad step.”(VDL), LexingtonReprinted from the Lloyd’s Equine Diseasecatastrophic event is the culmination ofrepetitive wear and not an isolated incident caused by a “bad step” or a “holein the track.” By carefully examiningthe horse, the pathologist can documentthe acute, catastrophic injury as well asthe underlying pathology. Additionally,he or she can note nonmusculoskeletalhealth issues.Mortality reviews are conductedwith the trainers, the equine medicaldirector, and the stewards followingcatastrophic breakdowns. The goal ofthese reviews is not to place blame, butto educate and implement strategies toprevent similar injuries going forward.The horse’s overall health and condition, his training and racing records,and the post-mortem exam outcome arereviewed in the hope of identifying riskfactors for that particular horse and opportunities for future intervention.Additionally, it is hoped that thetrainer will disseminate the knowledgegained by sharing their experiencewith others, including those who workin their barn, friends, and colleagues.Health issues that might not have beenclinically apparent but are identifiedon post-mortem examination can beaddressed, with informative conversations regarding such things as exerciseinduced pulmonary hemorrhage andgastric ulcers. In a very complicated4Quarterly, April 2018, Volume 27, Number 2.Deworming Horses:Dealing WithDiffering OpinionsMy senior gelding is out for a leasetrial. At home he lives in a drylot,and his fecal egg counts always showhim to be a 0 shedder, so I treat himtwice a year with a product thatincludes praziquantel for tapeworms.QAlexandra Beckstett/The HorseIoften answer the question, “Whywould someone want a post-mortemexam on an animal?”As a veterinary pathologist involvedin a necropsy program for racehorsesthat have sustained injuries on theracetrack, I get much the same questionfrom both lay people and professionalsin the horse industry.Most people understand why apost-mortem is warranted in a case ofsudden death but understanding theneed for a necropsy on a horse thathas sustained a catastrophic musculoskeletal injury might be less clear.Like all athletes, Thoroughbred racehorses experience a consistent patternof repetitive use wear associated withtheir musculoskeletal systems. Ananalogy familiar to most is the term“tennis elbow.” Likewise, “TommyJohn” surgery for baseball pitchers is acommonly recognized term, as rotatorcuff injuries also are a familiar maladyin quarterbacks.The association between pre-existinglesions and catastrophic injuries hasbeen documented for many years, beginning with the flagship post-mortemprogram instituted in California. Morethan 80% of racehorses that suffer afatal musculoskeletal injury have preexisting underlying pathology relatedto the fracture, indicating that the final6393—UK Veterinary Diagnostic LaboratoryKeeping pastures and paddocks free of manurecan help reduce the number of anthelmintictreatments horses require.
Bluegrass Equine Digest ca.uky.edu/equine TheHorse.com June 2018Deworming HorsesThe barn he is moving to is impeccably clean and has excellent manure management. There, he will get turnout time inshared grass paddocks. However, this farm does not do fecalegg counts and still uses an eight-week rotational program onall the horses. I tried to explain the current recommendationsfor parasite control to the owner but to no avail.Our agreement is that I will manage my horse’s parasiteprogram separate from the farm’s. But I’m concerned that heis at risk because of the barn’s practices, although I’m happythere is never manure left on the paddocks. Should I be concerned, and what’s the best way to protect him from internalparasites while he lives there?—Ashley, via e-mailDisease Mapping InitiativeFeatured MapStreptococcus equiThis month’s featured map is Streptococcus equi subspecies equi (S. equi), the causative agent of strangles.This contagious upper respiratory disease causes inflamed lymph nodes in the upper airway and trachea. Clinical signs include nasal discharge from the abscessed lymphnodes draining externally or into the guttural pouches(blind-end sacs connected to the throat in horses).As of June 18, the UKVDL has seen seven cases in Juneand saw 17 cases in May.Individuals with questions or concerns about diseaseoutbreaks can contact the UKVDL at 859/257-8283.Thank you for your question. Your situation is notunusual at all. We recently published results from aU.S.-wide survey showing that a large proportion of horseowners do not follow the current recommendations. So, thisbarn manager is definitely not alone in her managementtechniques. This begs the question: What are we (the researchers) doing wrong in communicating our recommendations? But that is a topic for anoth
Jenny Evans, MFA, co-managing editor and senior veterinary science marketing and promotion specialist, jenny.evans@uky.edu Holly Wiemers, MA, APR, co-managing editor and communications director of uk ag equine Programs, holly.wiemers@uky.edu Bluegrass Equine Digest
Utilize knowledge of equine anatomy and physiology to make equine management decisions. Communicate effectively with members of the equine industry. Requirements Major Course Requirements Equine Farm Operations I - 4 hours Equine Farm Operations II - 4 hours Introduction to Equine Studies - 3 hours Equine Healthcare Management - 3 hours
Manufacturing, University of Kentucky, Lexington, KY 40506 USA, and also with the Department of Electrical and Computer Engineering, University of Kentucky, Lexington, KY 40506 USA (e-mail: qiyue.wang@uky.edu; wenhua.jiao@uky.edu; rui.yu@uky.edu; yuming.zhang@uky.edu). M. T.
student contribution and participation within UK's Equine Initiative. (And because there will be free snacks and beverages!) Suggestions, comments, past experiences and your involvement are re-quested for the future success of student programs through the Equine Initiative. If you have ideas or want to be a part of this decision making process,
Mastering Equine - Advanced Horsemanship Mastering Horses The purpose of the Mastering Horses project is to help you to further develop skills in all areas of equine management. By setting goals to become a responsible horse owner and a good rider, you will become strong in the areas of self-discipline, patience, responsibility, respect
NYS 4-H Equine Show Rule Book TABLE OF CONTENTS I. INTRODUCTION Page NYS Equine Event Memo and Policy 5 NYS 4-H General Equine Show Rules 11 II. SHOW DIVISION RULES Cross Divisional Classes Showmanship at Halter 19 Trail 29 Costume 35 Dressage 37 Mounted Games 69 Drill/Parade/Quadrille 83 Hunt Seat 99 Saddle Seat 109
RADIOLOGY OF THE EQUINE LIMBS Lameness is one of the most important clinical abnormalities in horses - both in frequency and in economic impact. Radiography is often the first method of diagnostic imaging used in the evaluation of lameness. The majority of radiographs of the distal portions of equine limbs are obtained with portable x-ray units
Sep 10, 2011 · UK Equine Farm and Facilities Expo to be held Sept. 28 at Spendthrift Horse Farm University of Kentucky ooperative Extension Service and Ag Equine Programs will host the annual Farm and Facilities Expo from 3:30 - 8 p.m. EDT Tuesday, Sept. 28, at the famed Spendthrift Farm, 247 Swigert A
reading comprehension. DIRECTIONS. this practice test contains one reading selection with two multiple-choice questions and one open-response question. Mark your answers to these questions in the spaces provided on page 5 of your practice test answer document. 1. The porcupine is a controversial, yet important, forest creature. Our more prickly encounters with “quill pigs” may be remedied .
