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item Ashwell, Melissa
item Rexroad Jr, Caird
item Miller, Robert
item Vanraden, Paul

Submitted to: BARC Poster Day
Publication Type: Abstract Only
Publication Acceptance Date: 12/15/1995
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Marker-assisted selection (MAS) uses genetic marker genotypes to predict an animal's production potential and will provide additional information for progeny testing. To implement MAS, quantitative trait loci (QTL) must first be identified and then manipulated with the aid of linked markers.The objective of this study was to identify QTL for mastitis, as measured by somatic cell score (SCS), in an existing Holstein population. The initial search screened the genome for QTL in 7 Holstein families using selective genotyping. Ninety microsatellites were used to genotype the grandsires and their selected sons, using the granddaughters' values as trait endpoints. sons from each tail of the SCS distribution were selected for genotyping, reducing the number of genotypes needed while retaining enough power to detect QTL. The initial analysis identified many markers that revealed significant effects in at least 1family. Many of these effects may occur by ychance due to the large number of significance tests, so efforts were focused on genotyping additional sons at markers that revealed significant effects in 2 or more families. The first marker (BM3628; chr.22) showed significant effects in 2 families using selective genotyping, however,these effects were no longer significant after additional sons were genotyped. Another marker (513; chr. 23) revealed significant effects in 2 families using both selective and "complete" genotyping. In the future producers may be able to manipulate the QTL near 513 to reduce mastitis occurrence in these Holstein families.