DNA情報の家畜育種への活用-とくに乳牛について [in Japanese] Applications of DNA Information to Animal Breeding Programs with a Special Reference to Dairy Cattle [in Japanese]
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The identification of candidate genes or genetic markers by DNA-based technology offers a great potential to speed up the genetic improvement of animal productivity. The use of DNA information is expected to accelerate genetic progress through 1) increasing the accuracy of selection, 2) reducing the generation interval, 3) increasing selection differentials, and 4) efficient transfer of favorable genes from a donor to a recipient population. When desirable QTLs (Quantitative Trait Loci) are identified, direct genotypic selection on QTL is possible and effective. Even if QTL information is not available, genetic markers linked to the QTL can be utilized for marker-assisted selection (MAS). Linkage disequilibrium between marker and QTL alleles within families is required for MAS in animal population, particularly in dairy cattle. Genetic markers can be used for within-family selection such as top down and bottom up programs in dairy cattle, which enables the pre-selection of young bulls for progeny testing. The use of advanced reproductive technologies is a prerequisite to realize the potential genetic gain. Direct selection on QTL or marker-assisted selection offers the greatest advantage when the heritability of the trait is low. The importance of genetic markers decreases when phenotypic records or estimated breeding values are available. However, genetic markers or candidate genes have potential applications for improving sex-limited traits or traits not directly measurable such as carcass traits. Marker-assisted introgression using backcrossing is an alternative approach to incorporate the desired alleles. The efficiency of the introgression depends on the genetic value of the final product of the crossbred compared to the recipient population under continued selection. In this respect, some revised steps to increase production level in crossbreds are reviewed. Both position and effect of QTL have to be measured with prediction error variance so that its influence on selection response can be clearly determined. Thus, breeding system incorporating DNA information can be realized with prediction error variances even if QTL are not identified. DNA information would provide many clues not only to productivity but reproduction or disease resistance. DNA information would be a vital clue to improvement for lifetime/overall productivity influenced by productivity, reproduction and disease resistance.
- Nihon Chikusan Gakkaiho
Nihon Chikusan Gakkaiho 71(10), J447-J458, 2000-10-25
Japanese Society of Animal Science