A quantitative trait locus for body conformation maps to bovine chromosome one in Japanese Black cattle

Chromosomal regions of bovine chromosome one were scanned for the detection and mapping of segregating QTL influencing preweaning withers height, hip height, hip width, body length, chest width, chest depth, shoulder width, lumbar width, pin bone width, rump length, canon circumference, heart girth, abdominal width and abdominal girth. QTL analysis was performed by genotyping 132 half-sib progeny of 5 Japanese Black sires using 108 microsatellite DNA markers. Genotyped data on progeny and their sires were combined in a multi-point approach to calculate Identity-By-Descent (IBD) probability coefficients of inheriting allele 1 or 2 from the sire at specific chromosomal locations. The phenotypic data on progeny were regressed on these IBD coefficients in a within-common-parent regression analysis. A linear model containing the fixed effects of sex, parity and season of birth as well as age as a covariate, was fitted to the IBD coefficients and phenotypic data. Data were analyzed using QTL Express by generating an F-statistic through permutation tests at chromosome-wide significance thresholds over 1,000 iterations at 1cM intervals. A significant QTL for chest width was detected at 91cM in Sire 3. Suggestive QTL for thurl width, hip height, chest depth and abdominal girth were all located at 18cM in Sire 2. Other suggestive QTL detected were withers height (58cM) in Sire 5 and rump length (11cM), withers height (77cM) and chest depth (81cM) in Sire 1. The detection of these QTL boosts the prospect of implementing marker-assisted selection for body conformation traits in Japanese Black beef cattle.