HESTEFORSK Mapping performance, genetic variation and health in the Coldblooded trotter H-15-47-075

This comprehensive, ambitious SLU - NMBU collaborative study?s objective was to improve the performance, health and welfare of the Norwegian/Swedish Coldblooded trotter (CBT). Experts in Equine clinical veterinary medicine, performance evaluation, and genetic testing analyzed the genome of this horse breed for: 1) race performance enhancing genes; 2) assessed the degree of genetic diversity and inbreeding; and 3) genes that could predispose to dynamic laryngeal collapse (a very serious upper respiratory tract obstructive disorder that is unusually common in this breed of horse). Additionally the benefit of 4) Premie races was assessed; and the 5) racing longevity of this breed determined. A summary of some of the major findings is presented below. Previous studies have shown that a mutation in the doublesex and mab-3 related transcription factor 3 (DMRT3) gene has a major impact on racing performance of harness racehorses. The results of this study suggest no association of the DMRT3 mutation with precocity (i.e. performance at 3 years of age) in CBTs. The frequency of the AA genotype was significantly lower in the raced CBT sample compared with the unraced sample, and less than 50% of the AA horses participated in a race. Although suggested as the most favorable genotype for racing performance in Standardbreds and Finnhorses across all ages, the AA genotype does not appear to be associated with superior performance, early or late, in the racing career of CBTs. Dynamic laryngeal collapse (DLC) associated with poll flexion is common in CBT?s and other gaited horse breeds which exercise with high head carriage. This study revealed no direct association between DMRT3 gene and DLC in CBT?s; however, several candidate genes were identified which may be required for manifestation of this debilitating airway disorder warranting further investigation. To identify genomic regions associated with harness racing success a genome-wide association analyses with three racing performance traits (career earnings, number of gallops, best kilometer racing time) was performed in 613 CBT?s. Multiple genes related to intelligence, energy metabolism, and immune function were identified as potential candidate genes for harness racing success. So apart from the physiological requirements needed for a harness racing horse to be successful, the results of the current study also advocate learning ability and memory as important elements for harness racing success. This was a sensational finding, as it is the first study internationally to identify certain mental traits/ learning as a requirement for athletic success in mammals. These landmark findings have opened a new door in the research of athletic performance ? the role of the brain in athletic success. Since the 1950s, the Norwegian-Swedish Coldblooded trotter (NSCT) has been intensively selected for harness racing performance. As a result, a remarkable improvement in the racing performance of NSCTs has occurred; however, this improved racing performance has also been accompanied by a gradual increase in inbreeding levels. Inbreeding in NSCTs has historically been monitored using traditional methods based on pedigree analysis, but with recent advancements in genomics, the CBT industry has indicated a desire to adopt molecular approaches to the selection and maintenance of their breed. Our study demonstrated genomic inbreeding coefficients were higher than pedigree inbreeding coefficients with both methods showing a gradual increase in inbreeding levels in NSCTs between 2000 and 2009. Opportunities now exist for the CBT industry to develop programs that provide breeders with easily interpretable feedback on regions of the genome that are suboptimal from a genetic merit perspective or that are sensitive to inbreeding within the population. CBTs can participate in premie races as two year olds, where prize money is awarded for finishing the race within a specific time interval rather than winning. We evaluated the association between premie race participation and future competitive racing success. Our findings revealed that premie races are made up of horses with limited talent, as well as those with elite potential. These premie races seem to serve the important purpose of screening out young horses lacking in talent so that further economic loss is avoided. Only 51.5% of CBTs born between 2000 and 2009 started in one or more races. Participation in premie races was found to be associated with increased racing success in those horses that went on to compete in Para mutual races. The vast majority of CBTs do not start their formal racing careers until they are 3 years of age. Initiating racing at this age was associated with longer careers. An increased age beyond this at first start increased the hazard rate of retirement in this breed. Therefore premie racing as 2 year olds, and thereafter commencing the race careers as 3 year olds seems optimal for this breed.

This SLU - NMBU collaborative study seeks to improve the performance, health and welfare of the Norwegian/ Swedish Coldblooded trotter. Experts in Equine clinical veterinary medicine, performance evaluation and genetic testing will analyze the genome of this horse breed for: 1) race performance enhancing genes; 2) assess detrimental effects of inbreeding; and 3) genes that could predispose to dynamic laryngeal collapse (a very serious upper respiratory tract obstructive disorder which is very common in this breed of horse - relative to Standardbred trotters and Thoroughbred racehorses). Such genetic evaluation has the potential improve the health and sustainability of the Coldblooded racing trotter, and aids in setting objective goals regarding the breeding of these horses in Norway and Sweden. The project seeks to also train a research associate with the intension of this person becoming a graduate (PhD) student in the genetic assessment of Equine health & performance.