Estimation of Quantitative Trait Loci Parameters for Milk Production Traits in German Holstein Dairy Cattle Population

Abstract

The main objective of this study was to estimate the proportion of total genetic variance attributed to a quantitative trait locus (QTL) on Bos taurus autosome 6 (BTA6) for milk production traits in the German Holstein dairy cattle population. The analyzed chromosomal region on BTA6 spanned approximately 70 cM, and contained 6 microsatellite markers. Milk production data were obtained from routine genetic evaluation for 4500 genotyped German Holstein bulls. Technical aspects related to the estimation of model parameters for a large data set from routine genotype recording were outlined. A fixed QTL model and a random QTL model were introduced to incorporate marker information into parameter estimation and genetic evaluation. Estimated QTL variances, expressed as the ratio of QTL to polygenic variances, were 0.04, 0.03, and 0.07 for milk yield; 0.06, 0.08, and 0.14 for fat yield; and 0.04, 0.04, and 0.11 for protein yield, in the first 3 parities, respectively. The estimated QTL positions, expressed as distances from the leftmost marker DIK82, were 18, 31, and 17 cM for milk yield; 25, 17, and 9 cM for fat yield; and 16, 30, and 17 cM for protein yield in the 3 respective parities. Because the data for the parameter estimation well represented the current population of active German Holstein bulls, the QTL parameter estimates have been used in routine marker-assisted genetic evaluation for German Holsteins.

Accuracy of Prediction of Gene Content in Large Animal Populations and its Use for Candidate Gene Detection and Genetic Evaluation

“…Small effects appeared to be most overestimated. However, the results of this simulation study may not prove whether the presented method is superior in its detection power to traditional methods such as that used by Szyda et al (2005). Using the same data and a very similar approach to that of Szyda et al (2005), the results obtained were nearly identical with this method (results not shown).…”

“…However, the results of this simulation study may not prove whether the presented method is superior in its detection power to traditional methods such as that used by Szyda et al (2005). Using the same data and a very similar approach to that of Szyda et al (2005), the results obtained were nearly identical with this method (results not shown). However, the present method is easier and more general because it accepts genotypes from any genotyped animal and integrates smoothly into existing genetic evaluation models of any size and kind.…”

QTL mapping for production traits in Czech Fleckvieh cattle

“…Schrooten et al (2004) reported QTL at similar position (113 cM) but with effect on PP and PY in Holstein-Friesian cattle. Szyda et al (2005) also detected QTL with effects on PY, FY, and MY between 9 and 30 cM in German Holstein cattle.…”

“…Significant QTL were often found on chromosome 6 and were associated mostly with protein percentage (PP) and fat percentage (FP), and then also with yield traits -milk yield (MY), protein yield (PY), and fat yield (FY) (Freyer et al, 2003;Ashwell et al, 2004;Olsen et al, 2004;Szyda et al, 2005;Chen et al, 2006;Kučerová et al, 2006). QTL reported on BTA7 affected FY and FP Weller et al, 2008).…”

Polymorphism of the beta-casein gene and its associations with breeding value for production traits of Holstein–Friesian bulls

“…One of these regions -casein multilocus -consists of 4 loci and is very conservative in its organization and expression (Rijnkels et al, 2003). Szyda et al (2005) showed significant evidence of BTA6 QTL in shaping milk performance traits variation (for fat yield, the effect of this QTL amounts to 14%, for milk and protein yield -7 and 11%, respectively).…”