Qualification status and estimation of breeding value in French trotters

The objective of this study was to review the current selection model for French trotters. Data were obtained from the French central registration system for horses-and contained records of performance at the age of 2 through 6 of 183,955 trotters born between 1975 and 1994, and 46,629 of their mothers born after 1966. Genetic parameters were obtained for six traits that could be included in a revised model. Because of the absence of selection of mares in this breed, maternal -offspring regression analysis was used to estimate heritabilities and genetic correlations. Parameters were estimated per age, per trait and over the whole career. Heritabilities were generally moderate except for number of starts, which were low (0.07-0.13) and earnings at the age of 6 (0.13). Regarding estimates per age, genetic correlations between binary traits and performance traits were generally high (0.52-0.99 for earnings and [-1.00]-[-0.53] for best time). Binary traits were all genetically similar in relation to performance traits. Regarding estimates per trait, genetic as well as phenotypic correlations decreased with increasing age difference. Heritabilities for career traits were generally higher than those for age traits. It was concluded that a model based on career traits could very well be used for the selection of French trotters, for both scientific and practical reasons. This model would then contain three traits: qualification status and career earnings as index traits and number of starts as covariable. (C) 2004 Elsevier B.V All rights reserved.