Estimation of genetic trend in racing performance of thoroughbred horses

Abstract

Thoroughbred horses have been bred exclusively for racing in England since Tudor times and thoroughbred horse racing is now practised in over 40 countries and involves more than half-a-million horses worldwide. The genetic origins of the thoroughbred go back largely to horses imported from the Middle East and North Africa to England in the late seventeenth and early eighteenth centuries. Since the establishment of the Stud Book in 1791, the population has been effectively closed to outside sources, and over 80% of the thoroughbred population's gene pool derives from 31 known ancestors from this early period. Despite intense directional selection, especially on the male side, and the generally high heritabilities of various measures of racing performance, winning times of classic races have not improved in recent decades. One possible explanation for this is that additive genetic variance in performance may have been exhausted in the face of strong selection. To test this, we have estimated the genetic trend in performance over the period 1952-77 using TIMEFORM handicap ratings which are based entirely on the horse's own performance, and express its racing merit as a weight in pounds which the compilers believe the horse should carry in an average free-handicap race. These ratings take into account such factors as the firmness of the ground, the distance and the level of the competition. Our results indicate that the failure of winning times to improve is not due to insufficient genetic variance in the thoroughbred population as a whole.

Selection for morphology, gaits and functional traits in Lusitano horses: II. Fixed effects, genetic trends and selection in retrospect

“…A positive genetic trend has been achieved in different equestrian disciplines, including dressage, show jumping, eventing and endurance (Ricard and Touvais, 2007;Thoren Hellsten et al, 2009;Viklund et al, 2011), but also in conformation aspects (Albertsdottir et al, 2011;Fioretti et al, 2005;Miglior et al, 1998). For racing performance, however, the results have been less consistent, because even though a positive genetic trend for speed has been reported for several breeds (Gaffney and Cunningham, 1988;Klemetsdal, 1992;Mota et al, 2005;Oki and Sasaki, 1996;Olsen et al, 2011;Willham and Wilson, 1991), no reduction in winning times has been observed for the major horse races over the last 50 years (Gardner, 2006). Several fixed factors are known to affect horse traits and performances, including the effects of sex, stud, year, event, etc., and they are often included in the statistical models used in genetic evaluations (Bruns et al, 2004).…”

Breeding racehorses: what price good genes?

“…Gaffney & Cunningham 1988). However, if the goal is to maximize lifetime prize winnings, then it seems clear that stud fees are not an honest signal of a stallion's genetic quality.…”

“…Both quantitative and molecular approaches have revealed genetic variation for key racing performance traits (Gaffney & Cunningham 1988;Hill 1988;Harrison & Turrion-Gomez 2006), and accurately assessing the genetic potential of candidate parents may therefore be critical to breeding successful racehorses (Bailey 1998). In particular, the owner of a thoroughbred mare should mate her with a high-quality stallion in order to maximize the probability of producing successful progeny.…”

Estimation of Variance Components and Genetic Trend for the Race Performance in Turkish Arabian horse

“…Bu özellikler için genetik parametreler ve hayvanların damızlık değerleri tahmin edilmekte ve seleksiyonda kullanılmaktadır (Gaffney and Cunningham, 1988;Oki and Sasaki, 1996;Belhajyahia et al, 2003;Dubois and Ricard, 2007;Langlois and Blouin, 2007;Thorén Hellsten, 2008;Bakhtiari and Kashan, 2009;Park, 2011). 43 üyeli Dünya Spor Atları Yetiştirme Federasyonuna (WBFSH) yaklaşık %80'i Avrupa'dan olmak üzere yıllık 130000 civarında tay kaydedilmektedir (Koenen and Aldridge, 2002).…”