A candidate‐SNP retrospective cohort study for fracture risk in Japanese Thoroughbred racehorses

Abstract

SummaryFractures are medical conditions that compromise the athletic potential of horses and/or the safety of jockeys. Therefore, the reduction of fracture risk is an important horse and human welfare issue. The present study used molecular genetic approaches to determine the effect of genetic risk for fracture at four candidate SNPs spanning the myostatin (MSTN) gene on horse chromosome 18. Among the 3706 Japanese Thoroughbred racehorses, 1089 (29.4%) had experienced fractures in their athletic life, indicating the common occurrence of this injury in Thoroughbreds. In the case/control association study, fractures of the carpus (carpal bones and distal radius) were statistically associated with g.65809482T/C (P = 1.17 x 10‐8), g.65868604G/T (P = 2.66 x 10‐9), and g.66493737C/T (P = 6.41 x 10‐8). In the retrospective cohort study using 1710 racehorses born in 2000, the relative risk (RR) was highest for male horses at g.65868604G/T, based on the dominant allele risk model (RR = 2.251, 95% confidence interval 1.407–3.604, P = 0.00041), and for female horses at g.65868604G/T, based on the recessive allele risk model (RR = 2.313, 95% confidence interval 1.380–3.877, P = 0.00163). Considering the association of these SNPs with racing performance traits such as speed, these genotypes may affect the occurrence of carpus fractures in Japanese Thoroughbred racehorses as a consequence of the non‐genetic influence of the genotype on the distance and/or intensity of racing and training. The genetic information presented here may contribute to the development of strategic training programs and racing plans for racehorses that improve their health and welfare.

Factors Associated with Mortality in Ontario Standardbred Racing: 2003–2015

“…These effects could reflect multiple factors, including biology, wear and tear, and pathophysiology, as well as genetic contributions [45]. Recent evidence suggests a sex-differentiated genetic predisposition to fracture that also relates to superior performance ability [46], implying selection for speed may simultaneously select for fracture predisposition, as may speed itself [15]. Imperatives that drive selection and work stresses reflect industry practices and expectations, and these same forces also influence how age and sex are associated with mortality.…”

Fractures in Thoroughbred racing and the potential for pre‐race identification of horses at risk

“…Genetic associations with stress fractures have been identified in elite human athletes 82 and the potential for genomic screening has been suggested for Thoroughbred racehorses 83–85 . However, a recent systematic review found few associations 86 .…”

“…Genetic associations with stress fractures have been identified in elite human athletes 82 and the potential for genomic screening has been suggested for Thoroughbred racehorses. [83][84][85] However, a recent systematic review found few associations. 86 The heritability of musculoskeletal injury has been reported from various populations 84,87,88 and evidence that certain genotypes may predispose individual horses to fracture has been obtained from molecular studies, 89 prompting some to speculate that targeted breeding strategies and/or genetic screening might be used to help reduce the incidence of fractures.…”

Expression of select mRNA in Thoroughbreds with catastrophic racing injuries

“…Unfortunately, these approaches may be cost prohibitive if used on a regular, screening basis and/or they may require general anaesthesia. Alternatively, others have suggested using genetic screening or predictive modelling to identify those horses at greatest risk for catastrophic injuries, 4,[32][33][34] though the utility of these approaches have yet to be proven. While the detection of biomarkers for equine injuries has also been explored, [35][36][37][38][39] their use has not been widely adopted, despite some reported success.…”