Standardbred crossbreeding in Trotteur Français horse population : A successful experiment ?

Abstract

The percentage of French trotters born in 2003 with Standardbred genes was 75 %. The mean value of the proportion of standardbredgenes of these horses was 16 % and so the average proportion of Standardbred genes in the whole population of French trotters was 12 %.The reason was mainly the use of the 1/2 American stallion Florestan and its offspring (33 %). The influence of the American stallionWorkaholic and its offspring was only 17 %. This crossbreeding was very different from the cross of the Holstein breed in Black and Whitedairy cattle during the 1980’s. There was no back cross with the American population but with the French population and the percentageof Standardbred genes was maintained by the superior use of stallions with American genes (31 offspring per year versus 13). The introductionof Standardbred genes has been achieved and the percentage of genes was stable due to mating between crossed horses. The highpercentage of French trotters with Standardbred genes contrasted with the small number of American founders: 13 ancestors were sufficientto explain 99 % of the Standardbred genes! The effect of Standardbred genes on race performance was favourable and linear. The effect was greater for the annual earning per start at 3 years (11 % of phenotypic deviation for 10 % of American genes) than for totalcumulated life earning at 5 years of age (7 % of phenotypic deviation). In any case this effect explained less than 2 % of the variability.