Confirming QTL for calving and fertility traits on bovine chromosomes 7 and 10 in German Holsteins

The aim of the study was to confirm previously detected quantitative trait loci (QTL) for calving and fertility traits on bovine chromosomes 7 (BTA7) and 10 (BTA10) in the German Holstein population. A granddaughter design consisting of 31 (BTA7) and 30 families (BTA10) with a total of 1432 (BTA7) and 1419 (BTA10) sons was used for confirmation studies. All half-sibs were genotyped for six markers on each chromosome. Phenotypes for calving traits were parity-specific daughter yield deviations estimated univariately via a sire model. Estimated breeding values from routine breeding estimation were used for fertility traits. QTL analyses were done by linear regression on QTL transmission probabilities at each cM on the respective chromosomal segment. Permutation testing was used to determine the chromosome wise critical values. Additionally, the Fisher exact test was used either for each chromosome and each trait separately (univariate approach) or for each chromosome across traits (multivariate approach). No significant QTL could be confirmed with permutation testing using the univariate approach. However, the hit excesses of segregating families provided some evidence for QTL affecting calving traits on both BTA7 and BTA10 and for fertility traits on BTA7. This evidence was supported by the results of the Fisher exact test across traits, which were highly significant for calving traits on both chromosomes and for fertility traits on BTA7.