Will horse genetics create better champions?

TRENDS in Genetics Vol.17 No.3 March 2001

http://tig.trends.com 0168–9525/01/$ – see front matter © 2001 Elsevier Science Ltd. All rights reserved. PII: S0168-9525(00)02202-2

166 ForumForumForum

Will horse genetics

create better

champions?

The Genetics of the Horse

edited by A.T. Bowling and A. Ruvinsky CABI Publishing, 2000. £85 hbk (512 pages) ISBN 0 85199 429 6

The wildprogenitor of themodern horsewas a smallherbivoreadapted to runfast to escapepredators.Domesticationoccurred 6000years ago, andsince then the

horse has had a fundamental role inhuman history because of its widespreaduse in transportation, agriculture and war.During the last few decades, the use ofhorses as working animals has declinedworldwide and virtually disappeared in thedeveloped countries. At present, horses areessentially used for sport and leisure. Theimportance of this species to contemporarysociety is often underestimated: not onlyare horses fascinating animals that inspiregreat passion, but the horse industry is ofsignificant financial importance.

The Genetics of the Horse provides acomprehensive review of the differentareas of genetics applied to breeding,health and conservation. The contributorlist includes some of the most qualifiedspecialists in the various fields. The book,which is accompanied by an exhaustivebibliography, is written for researchers,professionals working in the breedingindustry and veterinarians; however,most chapters contain some basicinformation for nonspecialists.

The goal of contemporary horse breedingis to produce animals suitable for activitiesas diverse as racing, jumping, dressage,cross-country, leisure riding, cattle herdingand showing, to mention only the mostpopular. But what are the characteristicsrequired for the different specialities? Thesport horse is an athlete, and its valuedepends mainly on performance incompetitions. Performance is the result of a complex combination of conformational,physiological and behavioural traits, which

are known to be mostly heritable, as well asfactors such as the trainer and rider. Speedis only one quality of a racehorse; equallyimportant are its temperament, the easewith which it can be trained and the healthof its limbs. Moreover, the temperamentand conformation required to win a race on the flat are very different from thosenecessary to win a high-level show jumping competition. Therefore, a goodknowledge of the genetic transmission of various traits will be crucial in futurebreeding programmes.

However, the field of horse genetics isnot well developed because of the longgeneration time, small number ofoffspring per mare, small size ofstudfarms, management costs requiringhighly specialized personnel andinsufficient investment in research. Inaddition, measuring an animal’s geneticimprovement by using its performance is problematic because the quality of ananimal competing at high level can only beevaluated many years after it is born. Thisis particularly true for show jumping anddressage horses where full maturity isreached at 7–9 years of age and top-levelmares are kept in competition for anextended period of their lifetime,impairing their reproductive capacity.

These limitations are expected to beovercome by the introduction of modernbreeding technologies such as artificialinsemination and embryo transfer, whichhave been developed relatively slowly inhorses compared with other farm species.The section of the book describing theapplication of new breeding technologiesto horses is excellent. These in vitrotechniques will permit selection of theparents or sibs on the basis of extensiveperformance data. Another relevantachievement will be the generation ofnumerous offspring from champion mares

competing at high level, using surrogatemothers. Good results have been alreadyobtained, including production of identicaltwins by embryo splitting, but cloningfrom somatic cells has not yet beenattempted. The idea of generatingidentical copies of a champion remains adream for horse lovers and breeders.

The construction of genetic and physicalmaps of the horse genome is finallyunderway, but marker density is still low.A Horse Genome Project began in 1995with the aim of promoting internationalcollaboration in the field of horse genomics(http://www.uky.edu/Ag/Horsemap). Thestatus of horse gene mapping isextensively discussed in two chapters ofthe book. The results obtained so far areencouraging, with over 500 markerslocalized. By contrast, completesequencing of the genome is still beyondthe reach of the relatively small group oflaboratories involved in the project.

An important aspect to be considered isthat breeding for desirable performancetraits will tend to reduce genetic variation.In this scenario, autochthonous breeds (i.e.minor breeds native to a particular region)that are specialized for agriculture andtransportation are doomed to extinction. Forthe survival of horse diversity, conservationprogrammes should complement selectionfor performance traits.

Despite the fact that the section ongenome mapping is rapidly becoming outof date, this book will be an invaluablesource of information and should be on theshelf of everyone interested in the futureof horse breeding.

Elena Giulotto

Dipartimento di Genetica e Microbiologia,Adriano Buzzati Traverso, ViaAbbiategrasso 207, 27100 Pavia, Italy.e-mail: giulotto@ ipvgen.unipv.it

Ann Bowling

Ann Bowling, Executive Associate Director of the School of Veterinary Medicine atthe University of California and editor of The Genetics of the Horse, suffered a fatal

cerebral haemorrhage on the evening of 8 December 2000.

She is survived by her husband, Michael, and her daughter, Lydia. In lieu of flowers, thefamily ask that people contribute to the Ann Bowling Scholarship for Equine Genetics, whichhas been set up in remembrance of her. The scholarship will be awarded to a DVM studentwho is interested in pursuing a career in equine genetics. Contributions should be sent to:

The Ann T. Bowling Scholarship Fund for Equine Genetics, Office of Development, School ofVeterinary Medicine, One Shields Avenue, University of California, Davis, CA 95616, USA.