Mapping quantitative trait loci for bovine ovulation rate

An elite, three-generation Family from the USDA Meat Animal Research Center twinning population was examined for evidence of ovulation rate quantitati ve trait loci (QTL). This work was both a continuation of previously report ed results suggesting evidence for ovulation rate QTL on bovine Chromosome (Chr) 7 and an extension of a genome-wide search for QTL. Additional marker s were typed on Chr 7 to facilitate interval mapping and testing of the hyp othesis of one versus two QTL on that chromosome. In addition, 14 other inf ormative markers were added to a selective genotyping genome screening of t his family, and markers exhibiting nominal significance were used to identi fy chromosomal regions that were then subjected to more exhaustive analysis . For Chr 7, a total of 12 markers were typed over a region spanning the pr oximal two-thirds of the chromosome. Results from interval mapping analyses indicated evidence suggestive of the presence of QTL (nominal P < 0.00077) within this region. Subsequent analysis with a model postulating two QTL p rovided evidence (P < 0.05) for two rather than one QTL on this chromosome. Preliminary analysis with additional markers indicated nominal significanc e (P < 0.05) for regions of Chrs 5, 10, and 19. Each of these regions was t hen typed with additional markers for the entire three-generation pedigree. Significant evidence (P < 0.000026) of ovulation rate QTL was found for Ch rs 5 and 19, while support on Chr 10 failed to exceed a suggestive linkage threshold (P > 0.00077).