Leukocyte telomere length in the Thoroughbred racehorse

Abstract

Thoroughbred racehorses possess superior cardiorespiratory fitness levels and are at the pinnacle of athletic performance compared to other breeds of horses. Although equine athletes have undergone years of artificial selection for racing performance, musculoskeletal injuries and illnesses are common and concerns relating to animal welfare have been proposed. Leukocyte telomere length is indicative of biological age, and accelerated telomere shortening occurs with excess physical and psychological stress. This study was designed to explore the association between leukocyte telomere length, biological factors (age, sex and coat colour), training status, winnings and race history parameters. Blood was collected from 146 Thoroughbred racehorses from around Geelong, Victoria, Australia. DNA was extracted from leukocytes; telomere length was measured using qPCR and analysed in context with traits obtained from the Racing Australia website. Age was inversely correlated with telomere length (r = -0.194, P = 0.019). The oldest horses (≥11 years) in the highest age quartile possessed shorter telomeres compared to younger horses in the first, second and third quartiles (≤2, 3-5 and 6-10 years respectively; P < 0.05). No statistically significant associations were observed between telomere length and biological factors, training status, winnings or race history parameters in age-adjusted analyses. The study findings suggest that Thoroughbred horses may undergo age-related telomere shortening similar to other mixed breeds and humans. Despite concerns from some quarters regarding the welfare of racehorses, there was a lack of accelerated biological ageing observed in the present study, as indicated by leukocyte telomere length.

Telomere Dynamics in Livestock

“…There were no statistically significant correlations between TL and performance-based (competitive racing) history records (race winnings, the number of races entered, or minimum or maximum distances of entered races). There were no associations between TL and other economically relevant traits in the equine industry, such as sex or coat color [110].…”

“…In Thoroughbred horses, the average annual shortening of telomeres from peripheral blood mononuclear cells was 134 bp per year [111]. There was substantial inter-animal variability in TL of younger animals [110]. The variability in growth rates in younger animals, health status at the time of collection, and genetics could contribute to the high variability in leukocyte TL.…”

Exercise regulates shelterin genes and microRNAs implicated in ageing in Thoroughbred horses

“…To examine if the molecular mechanisms governing shelterin and TERT gene expression are affected by exercise, we used a large animal model of excellent aerobic fitness. Our previous work established that telomere length is inversely related to age in Thoroughbred horses [9] and that telomeres in these large mammals are much more similar in length to that of humans than in small animal models, such as rodents [15,20]. Unlike mice and rats, but like humans, telomerase activity is very low or absent in somatic cells from large animals.…”