Submitted to: Journal of Animal Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 12/7/2001
Publication Date: 5/1/2002
Citation: Li, C., Basarab, J., Snelling, W.M., Benkel, B., Murdoch, B., Moore, S.S. 2002. The identification of common haplotypes on bovine chromosome 5 within commercial lines of Bos taurus and their associations with growth traits. Journal of Animal Science 80:1187-1194. Interpretive Summary: Chromosomal regions influencing a trait can be detected by relationships between alternative forms of DNA markers and observations for a trait in populations designed to reveal associations between traits and individual markers. In other populations, regions of a chromosome affecting a trait may be detected by combinations of adjacent markers passed from parent to offspring. Where particular combinations of two markers are strongly associated with a trait, the segment of the chromosome between those two markers is expected to contain genes that influence the trait. Here we report combinations of markers on cattle chromosome 5 and their association with growth traits. One hundred seventy six bull calves and their 12 sires from an Angus-based seedstock line, selected for maternal traits over 30 years, were genotyped using 16 DNA markers. In order to verify the results from the maternal line, another 170 bull calves and their 14 sires from a line selected for calving ease were genotyped using nine markers. Ten combinations of adjacent markers in three segments of chromosome 5 showed significant associations with birth weight, preweaning gain, and postweaning gain on feed in the maternal line. Nine marker combinations in the same three chromosomal regions, were associated with growth in the calving ease line. These results provide a useful reference to identify genes affecting growth within each of these regions, and ultimately develop DNA tests to assist selection for growth.
Technical Abstract: The cosegregation between a genetic marker and the QTL in a well-designed mapping population is the basis for successful QTL mapping. Linkage disequilibria are, however, also expected among individuals that descended from the same breeding line, and some common haplotypes should carry on and segregate among individuals of the line. These identical by descent haplotypes make it possible to identify and locate the QTL segregating in the line. We report the identification of common haplotypes within commercial lines of Bos taurus and their associations with growth traits. One hundred and seventy six male calves and their 12 sires (9 to 30 male calves of each sire) of the Beefbooster, Inc., M1 line selected for maternal traits over 30 yr were genotyped using 16 microsatellite markers chosen from bovine chromosome 5 for the initial haplotype and growth association analysis. In order to verify the results from the M1 line, another 170 male calves and their 14 sires from the Beefbooster M3 line were genotyped using nine microsatellite markers chosen from bovine chromosome 5. The alleles of each male calf contributed by the sire and by the dam were identified, and haplotypes in the M1 line were established along 93% of bovine chromosome 5. The haplotypes in the M3 line were established along the chosen regions of bovine chromosome 5. Regression analysis detected 10 haplotypes in three chromosomal regions (0 to 30 cM, 55 to 70 cM, and 70 to 80 cM) that showed significant associations with birth weight, preweaning average daily gain, and average daily gain on feed in M1 line and 9 haplotypes associated with the growth traits in the same chromosomal regions in the M3 line at the comparisonwise threshold level. On average, the 19 haplotypes have an effect of 0.68 SD on the growth traits, ranging from 0.41 SD to 1.02 SD. The results provide a useful reference for further positional candidate gene research and marker-assisted selection.