All breeders intuitively understand genetics, since pedigrees are visual representations of the inherited proportion of the variation in racing performance. Selection for superior racecourse performance during the past 300 years of Thoroughbred breeding has resulted in an elite athlete capable of speed and stamina. Since the horse genome sequence became available in 2007, many of the genes contributing to the elite athletic physiology and physique of the Thoroughbred have been identified: these include genes responsible for insulin signalling, metabolism of fats and muscle strength.

What is the horse genome?

The genome is the complete complement of genetic material within an individual and carries the instructions for building and maintaining a living organism. The genetic material, known as DNA, is made up of the letters G, A, T and C. Various combinations of these letters make up the 3 billion letters of the genetic code. Approximately 25,000 genes are found within the genome, each gene spelling out the recipe for a particular protein. Proteins are the building blocks of cells and are the physical representation of the genetic information encoded in the DNA of the genome.

The common query “Has he got the gene?” is misleading. All individuals have the same number of genes. The differences between individuals result from differences in the ‘spelling’ of the DNA within genes. The DNA code for a particular gene may differ between individuals resulting in a difference in the protein and the expression of the trait. The simplest example is coat colour. Coat colour variation is a result of differences in the DNA code for genes contributing to skin and hair pigmentation. “Has he got the right type of gene?” is therefore more appropriate.

Are racehorses born or made?

The success of a racehorse depends on a combination of inherited characteristics (genes) and environmental influences including management and training. Pedigree studies have demonstrated that more than 35 percent of the variation in racecourse performance is due to inherited characteristics. In a situation where individuals are cared for and trained in the same way, the genetic contribution to racing performance will be considerably more important. In other words, all other things being equal, the main differences between two individuals in a yard will be in the genes.