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United States Department of Agriculture

Agricultural Research Service

Title: Implications of Cloning for Breed Improvement Strategies: Are Traditional Methods of Animal Improvement Obsolete

Author
item Van Vleck, Lloyd

Submitted to: Journal of Animal Science Supplement
Publication Type: Abstract Only
Publication Acceptance Date: March 1, 1998
Publication Date: N/A

Technical Abstract: No!! Unless? Can the optimum animal be defined? Will that definition change over time, by location? First, assume what may be impossible, that the perfect animal can be defined! Then, can the "perfect" animal to match the definition be found? Suppose such an animal is found. "Is the animal perfect because of phenotype or genotype?" In other words, the P = G + E problem exists which requires traditional improvement methods to determine whether G, E or a combination leads to perfection. For most traits, additive genetic variance accounts for 10 to 50% of total variance. Cloning the "perfect" animal would eliminate that variance and could also capture optimum dominance and epistatic genetic effects that may account for additional variation. For some traits maternal effects are important. Then clones as breeding animals must be "perfect" for both direct and maternal genotypes. Use of clones to increase uniformity could be only partially successful. If heritability is 25%, then the standard deviation among clones would be 87% of that of uncloned animals. Now limit the goal. Suppose an animal has a gene for low fat, well-marbled meat or same sex twins. Cloning would allow wide distribution of that gene but along with other genes of the designated animal. Again the P = G + E problem with the need to reduce the "bad stuff", save the desired gene, and increase the other "good stuff". Cloning, at best, is another tool for animal improvement that joins the list of previous biotechnological inventions, some of which have become cost-effective: artificial insemination; multiple ovulation and embryo transfer, sexing of semen, and in vitro fertilization. Cloning belongs in that inventory but use of cloning will need to be managed to be cost effective for improvement of quantitative characters.

Last Modified: 10/23/2014
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