ژنوتيپ كردن انتخابي در گزينش بكمك نشانگرهاي مولكولي طي آزمون نتاج گاوهاي نر جوان

Selective genotyping to use marker-assisted selection in progeny testing of young bulls

The extra genetic progress by using DNA information indicated that the genetic merit can enhance through increasing the accuracy of genetic evaluations across a population. This study investigated whether selection using genetic markers linked to quantitative trait loci (QTL) increased selection accuracy of potential young bulls for progeny testing experiment in marker-assisted selection (MAS) breeding scheme. Besides, the effect of selective genotyping in potential bulls as candidates for progeny testing on the accuracy of total estimated breeding values was studied based on stochastic simulation of a population resembling a commercial dairy cattle breeding scheme for 25 yr. Two levels of selective genotyping (20 and 50%) were performed to sample young bulls compared to either complete genotyping (100%) or no genotyping (0%o) of potential candidates. A trait with low heritability (h2=0.04) only expressed in females was used. One bi-allelic QTL with 25% of the genetic variance and 4 markers were simulated in an identified 4cM region of a chromosome in linkage disequilibrium. Using marker information in selection schemes indicated that the accuracies among the potential candidates were higher than conventional evaluations without including genotype information. In comparison to complete genotyping of young bulls during years 6-11, the superiority of using QTL information were 76-82% with 50% genotyping, 51-67%) with 20%) genotyping, and 46-55%) using conventional prediction methods. Lower accuracies were appeared in using genotypic information where favorable QTL allele was closed to fixation. Therefore, using a detected-QTL and selective genotyping during the young ages to identify the proper candidates (young bulls) can be considered as an efficient method to improve the selection accuracy with lower genotyping costs.