Genetic aspects of embryo transfer.
Use of embryo transfer can lead to increases in rates of genetic improvement from selection programs from as little as 5% to a maximum of near 100%, depending on species, trait, and extent of use of other tools such as A.I. In general, embryo transfer will have much less impact on rates of genetic improvement than A.I., and in a dairy cattle program where A.I. is used effectively, embryo transfer is likely to add less than 10% to rate of genetic improvement. The potential for increasing rate of genetic improvement appears to be greater in beef cattle. In any species with low reproductive rate, embryo transfer offers a potential means of rapidly increasing numbers of animals of a breed, strain, mutant genotype or group exceeding a stringent threshold; such use may be of considerable value to a specific genetic research or multiplication program. Maximizing selection intensity through combined use of A.I. and embryo transfer can lead to a rapid increase in inbreeding, and steps should be taken to avoid this in any population which it is desired to maintain in the long term. Embryo transfer offers an effective tool for research on maternal-fetal and fetal-fetal interactions, and in this way can make important indirect contributions to more efficient breeding programs. With improved embryo storage capability, embryo transfer has the potential for useful contributions in the areas of transfer of germ plasm between countries, preservation of rare breeds, and provision of genetically stable control populations.
Bradford
G E
GE
Department of Animal Science University of California, Davis, CA 95616 USA.
Kennedy
B W
BW