Horse racing: The performance of young, cold-blooded trotters – heredity, environment and muscular characteristics

In spite of large individual variations in muscular characteristics, it seems that the muscles of young, cold-blooded trotters have a relatively low oxidative capacity, which may be one of the reasons why this breed of horses often has a late debut on the horse-racing track.

This is one of the findings of Tobias Revold's doctoral research, in which he has studied factors affecting the probability of good racing performances in young, cold-blooded trotters. His thesis also describes the horses' muscular characteristics and how these can change as a result of training.

Less than a third of registered cold-blooded trotters will start participating in ordinary trotting races during the three-year season, even though the trotting speed of this breed has gradually increased over the last few decades.

Revold has studied 144 cold-blooded trotters born in 2005: the conditions in which they grew up, their size and the breeding index of their parents. He found that the parents' breeding index was the factor that had the greatest effect on whether a young horse began racing and on its chances of performing well during the three-year season.

In addition, Revold took tissue samples of the horses' posterior pelvic muscle (musculus glutaeus medius) and analysed the composition of muscle fibre types, the blood supply to the muscles and the activity of major muscle enzymes. His research showed that there were large individual variations in muscular characteristics amongst the horses in the trial, but that the oxidative capacity of the muscles (i.e. their aerobic combustion capacity) was generally lower amongst these horses than that previously seen in comparable breeds.

Revold also looked at how the muscular characteristics of 8 cold-blooded trotters changed during a two-year training period and how lactate transporters were positioned in the muscle tissue of these horses. In the course of the training period, Revold discovered that the composition of the muscle fibres changed into fibre types with a slower contraction speed and a higher oxidative capacity. The lactate transporter MCT1 was chiefly proven to be present in muscle fibre with a high oxidative capacity.

The research work was carried out at The Norwegian School of Veterinary Science (NVH) and at The Swedish University of Agricultural Sciences. Some analyses were also conducted at the University of Helsinki.

Tobias defended his doctoral thesis on 4^th June 2011 at The Norwegian School of Veterinary Science. The thesis is entitled: "Performance predictors and muscle characteristics in young Norwegian-Swedish Cold-blooded Trotters."