Comparisons of power for detection of quantitative trait loci (QTL) for carcass traits in Japanese black cattle utilizing progeny testing schemes

The objective of this study was to compare the power of half-sib (with and without selective genotyping) and grand-progeny designs for detection of quantitative trait loci (QTL) for carcass traits in Japanese Black cattle using data from progeny testing schemes. Power of QTL detection was calculated for a range of small to large QTL effects (0.1, 0.3 and 0.5 SD) and the type I error rate of 0.01. Two progeny sizes (10 or 50) were used assuming half-sib (without selective genotyping) and grand-progeny designs, and the progeny size of 500 was used for half-sib design with selective genotyping. Without selective genotyping, power increased with increasing number of sires and decreasing heritability in half-sib designs. When it was assumed that progeny size was 10 and heritability was 0.4, 191 sires were required to achieve reasonable power ( > 0.75) in half-sib designs (total 1,910 animals were genotyped), while only 44 sires with 10 grand-sires were required in grand-progeny designs (total 440 animals were genotyped). With selective genotyping, only 50 animals genotyped were required to achieve reasonable power for QTL having moderate effects. The results indicated that QTL could not be expected to be identified for carcass traits in Japanese Black cattle using data from the half-sib designs without selective genotyping. On the other hand, it was suggested that the grand-progeny designs and half-sib designs with selective genotying would be a useful tool for QTL detection of carcass traits in Japanese Black cattle.