Combining Gene-Based Methods and Reproductive Technologies to Enhance Genetic Improvement of Livestock in Developing Countries
Selection based on DNA markers is most useful for traits that are hard to measure and have low heritability. It allows earlier and more accurate selection, increasing short- and medium-term selection response, and may aid in targeting genotypes for specific production environments or markets. The use of genotypic information in breeding programmes for within-breed selection will generally have limited extra benefit, unless selection based on phenotype is difficult or advanced reproductive technologies are used. Novel reproductive technologies boost reproductive rates of breeding animals and may allow reproduction at juvenile ages. The benefit arises from increased selection intensity, as well as from increased selection accuracy due to larger families and decreased generation interval, as higher reproductive rates result in lower optimal ages for breeding animals. Increased reproductive rates and early selection rely more on between-family selection and potentially decrease effective population size, therefore increasing inbreeding. Selection needs to be optimized with respect to inbreeding and merit. Extra benefit from scenarios with unlimited use of reproductive technologies is restricted by the need to maintain genetic diversity. Benefits from marker assisted selection are higher in breeding programmes that use reproductive technologies, as the value of providing information about genotype is more beneficial for selection of young animals before they have a phenotype. Moreover, genotype information exploits variation within families, which is beneficial in breeding programmes where loss of genetic diversity is to be controlled. In developing countries, use of genotype information is likely to be most useful in marker assisted introgression programmes, where valuable genes are introgressed from one breed into another. A large variety of genetic resources in developing countries exists across breeds and populations, and utilization and management of this variation might greatly benefit from gene technologies.
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