Detection of genes influencing economic traits in three French dairy cattle breeds

Rachel Rupp,Marie Yvonne Boscher,Yves Amigues,André Neau,Rémi Faugeras,Hubert Levéziel,Frédérique Cerqueira,Didier Boichard,Florence Bourgeois,Cécile Grohs

doi:10.1051/gse:2002037

Abstract

A project of QTL detection was carried out in the French Holstein, Normande, and Montbéliarde dairy cattle breeds. This granddaughter design included 1 548 artificial insemination bulls distributed in 14 sire families and evaluated after a progeny-test for 24 traits (production, milk composition, persistency, type, fertility, mastitis resistance, and milking ease). These bulls were also genotyped for 169 genetic markers, mostly microsatellites. The QTL were analysed by within-sire linear regression of daughter yield deviations or deregressed proofs on the probability that the son receives one or the other paternal QTL allele, given the marker information. QTL were detected for all traits, including those with a low heritability. One hundred and twenty QTL with a chromosome-wise significance lower than 3% were tabulated. This threshold corresponded to a 15% false discovery rate. Amongst them, 32 were genome-wise significant. Estimates of their contribution to genetic variance ranged from 6 to 40%. Most substitution effects ranged from 0.6 to 1.0 genetic standard deviation. For a given QTL, only 1 to 5 families out of 14 were informative. The confidence intervals of the QTL locations were large and always greater than 20 cM. This experiment confirmed several already published QTL but most of them were original, particularly for non-production traits.

Highlights

Livestock species have been selected for a long time with the aim of improving traits of economic interest
This species concentrates many conditions unfavourable to phenotypic selection and, favourable to marker-assisted selection (MAS): most traits of interest are sex-limited; the generation interval is long; artificial insemination bulls should be progeny tested before extensive use, which is a long and costly step; the breeding schemes are more and more designed with bull dams selected before their first lactation on pedigree information only, in order to reduce the generation interval; last but not least, functional traits, such as disease resistance or fertility, have a low heritability but are more and more important in the breeding goal
MAS could be oriented towards increasing the genetic trend on the current objective or modifying the breeding objective by efficiently including low heritability traits, the breeders most likely will use it to decrease the cost of the breeding programme by reducing the number of bulls sampled

Summary

INTRODUCTION

Livestock species have been selected for a long time with the aim of improving traits of economic interest. It is believed that marker-assisted selection (MAS) could be profitable in dairy cattle This species concentrates many conditions unfavourable to phenotypic selection and, favourable to MAS: most traits of interest are sex-limited; the generation interval is long; artificial insemination bulls should be progeny tested before extensive use, which is a long and costly step; the breeding schemes are more and more designed with bull dams selected before their first lactation on pedigree information only, in order to reduce the generation interval; last but not least, functional traits, such as disease resistance or fertility, have a low heritability but are more and more important in the breeding goal. We present the results of a large QTL detection experiment carried out in the French dairy cattle AI populations

Material

Methods

RESULTS

QTL results

DISCUSSION AND CONCLUSION