Development of genetic models for estimation of racing performances in German thoroughbreds

Abstract

Abstract. The objective of this study was to develop new statistical models for genetic estimation of racing performances in German thoroughbreds. Analysed performance traits were "square root of rank at finish", "square root of distance to first placed horse in a race" and "log of earnings". These traits were found to be influenced by the carried weight, which was determined by the horse's earlier performance. Therefore, new traits were developed based on random regression models, which were independent from the carried weights. Heritabilities were first estimated for these created traits "new rank at finish" (h2 = 0.101) and "new distance to first placed horse in a race" (h2 = 0.142) by using two univariate animal models. When considering a linear regression of carried weights as fixed effect in the statistical model, heritabilities for "square root of rank at finish" (h2 = 0.086) and "square root of distance to first placed horse in a race" (h2 = 0.124) decreased. Breeding values of “new rank at finish” and "new distance to first placed horse in a race" were compared with breeding values of "square root of rank at finish" and "square root of distance to first placed horse in a race", in which carried weight was considered as fixed regression in the model. These two different models were compared by two criteria. Breeding values were overestimated for low performing thoroughbreds and underestimated for high performing horses when considering a linear regression of carried weights as fixed effect in the model. Statistical models considering new created traits ("new rank at finish" and "new distance to first placed horse in a race") which were independent of carried weights, showed better suitability for genetic estimation. Due to high genetic correlation with other traits and showing highest genetic variance a univariate animal model for the trait “new distance to first placed horse in a race” was recommended for genetic estimation.

Analysis of the Annual Earnings used as the Sire Evaluation Criteria in Home-produced Thoroughbred Racehorses

“…경주능력에 대한 평가형질들은 속도 (Oki et al, 1997;Mota et al, 2005), 부담중량 (Bugislaus et al, 2004), 승률 (Gillespie, 1971;Watanabe, 1974), 착순 (Tavernier, 1991;Sobczynska, 2006)과 수득상금 (Klemetsdal, 1994;Langlois & Blouin, 2004) 등으로 이들에 대한 다양한 연구가 이루어졌으며, BLUP (best linear unbiased prediction) 이론을 이용한 경주마의 유전능력 평 가는 1980년대 이후 폭 넓게 연구되어 왔다 (Arnason, 1982;Tavernier, 1988;Willham & Wilson, 1991;Belhajyahia et al, 2003;Langlois & Blouin, 2007;Sobczyńska, 2010). 국내 씨수 말들의 경주능력은 자마의 연간수득상금에 바탕을 두고 있는 평균 수득상금지수(Average earning Index, AEI)로 평가되고 있다.…”

Genetic analysis of distance-dependent racing performances in German Thoroughbreds

“…The trait »New distance to first placed horse over all distances« estimated with the univariate genetic-statistical model (3) had a value of h²=0.101. BUGISLAUS et al (2004) found a genetic correlation between »New distance to first placed horse« and »New rank at finish« of r g =1. So, there seems to be no difference between these traits that were both independent of carried weights.…”

“…The estimated coefficients were independent from the genetic potential of horses due to estimation within horses. BUGISLAUS et al (2004) compared two different considerations of raced horses' carried weights in genetic estimations and found that the inclusion of a fixed linear regression in the genetic-statistical model lead to overestimated breeding values for low performing Thoroughbreds and underestimated breeding values for high performing Thoroughbreds.…”

“…BUGISLAUS et al (2004) determined that the use of equation [1] is more suitable for the consideration of carried weights. Figure 1 Distributions of regression coefficients using random regression models of square root of distance to first placed horse in races over sprint-(1), mile-(2) and long distances (3) on carried weights…”

“…The genetic correlations between the traits Sprint, Mile, Intermediate and Long varied from r g =0.64 to 0.99 within age-class two and three and decrease with increasing distance difference. BUGISLAUS et al (2004) created the racing performance trait »new distance to first placed horse in a race« which was independent from carried weights of horses in races. This trait showed a good suitability for genetic evaluation.…”