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ARS Home » Northeast Area » Beltsville, Maryland (BARC) » Beltsville Agricultural Research Center » Animal Genomics and Improvement Laboratory » Research » Publications at this Location » Publication #319497

Title: Revisiting the “a posteriori” granddaughter design

Author
item Wiggans, George
item WELLER, JOEL - Volcani Center (ARO)

Submitted to: Interbull Annual Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 8/8/2015
Publication Date: 8/19/2015
Citation: Wiggans, G.R., Weller, J.I. 2015. Revisiting the “a posteriori” granddaughter design. Interbull Annual Meeting Proceedings. Interbull Bulletin 49:36–42.

Interpretive Summary: With the exception of a few genes, the actual polymorphisms that are responsible for detected gene loci of quantitative traits (QTLs) remain unknown. Determination of those polymorphisms should result in increased rates of genetic gain because their effects can be included directly in genomic evaluation to increase evaluation accuracy. In a previous study, a statistical technique called the a posteriori granddaughter design (APGD) was used to determine QTL genotypes for U.S. Holstein bulls with mid-or high-density genotypes. In this study, the APGD method was reapplied to the U.S. Holstein population using the more extensive data currently available to compare the results to the previous study and to other recent studies that have identified gene loci for quantitative traits in the U.S. and Australian dairy cattle populations. Thirty-three traits were analyzed: yield (milk, fat and protein and component percentages), milk somatic cell score, productive life, daughter pregnancy rate, heifer and cow conception rates, service-sire and daughter calving ease, service-sire and daughter stillbirth rates, 18 conformation traits and the net merit genetic-economic index. At least one significant effect was found for all but six traits. Results for yield traits corresponded to those for Australian Holsteins, and results for fertility traits generally corresponded to previous results for U.S. Holsteins. Results will be used to identify promising regions of sequence data for discovery of causative mutations.

Technical Abstract: An updated search for quantitative trait loci (QTLs) in the Holstein genome was conducted using the a posteriori granddaughter design. The number of Holstein sires with 100 or more genotyped and progeny-tested sons has increased from the previous 52 to 71 for a total of 14,246 sons. The bovine genome was divided into 621 segments of approximately 100 markers each. The sons of each bull were divided into two groups based on which paternal haplotype was transmitted to each son for each chromosomal segment. Significance was tested for each economic trait for each chromosomal segment by a linear model that included the effect of paternal haplotype nested within father. Thirty-three traits were analyzed: yield (milk, fat and protein and component percentages), milk somatic cell score, productive life, daughter pregnancy rate, heifer and cow conception rates, service-sire and daughter calving ease, service-sire and daughter stillbirth rates, 18 conformation traits and the net merit genetic-economic index. Fifty-five chromosomal regions met a significance criterion of probability of