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Title: PERFORMANCE OF HOLSTEIN CLONES IN THE UNITED STATES

Author
item Norman, H
item LAWLOR, T - HOLSTEIN ASSOCIATION
item Wright, Janice
item Powell, Rex

Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/11/2003
Publication Date: 3/1/2004
Citation: Norman, H.D., Lawlor, T.J., Wright, J.R., Powell, R.L. 2004. Performance of Holstein clones in the United States. Journal of Dairy Science. 87(3):729-738.

Interpretive Summary: Consumers are interested in knowing whether cloning and other forms of biotechnology impact food safety, and especially cloning. Cloning by embryo splitting and nuclear transfer was introduced during the 1980s but the performance of clonal families that result from the biotechnology had not been examined. This study documents phenotypic and genetic performance of US Holstein clones from embryo splitting and nuclear transfer for yield and fitness traits. A total of 2319 split embryo clones and 215 nuclear-transfer clones have been registered with the Holstein Association USA. Numbers of embryo-split male clones have decreased as have numbers of nuclear-transfer male clones. For clones to enhance the population genetically, their pedigree merit must be superior to that of the population. Animals selected for cloning were slightly superior genetically to population mean for yield traits. For females, mean superiority of pedigree merit of embryo-split clones compared with that of the population for the same birth year was 186 kg for milk, 9 kg for fat, and 7 kg for protein. For nuclear-transfer clones, superiority to population pedigree merit was 165, 10 and 8 kg, respectively. The advantage for male clones above the population pedigree merit was somewhat greater. The small pedigree advantage for clones of 1 standard deviation above breed mean indicates that the selection of animals to clone was not based primarily on production. Yield deviations of embryo-split clones for milk, fat, and protein were lower than those of their full siblings, which indicates a possible impact of the technology on performance. Yields of nuclear-transfer clones were not significantly different from those of their noncloned full siblings, and were based on small numbers. Those male clone pairs of apparent identical genotype received PTA from daughter yields more similar than did those from same technology that were confirmed by blood typing to be nonidentical. It is recommended that those embryo transfer split clones confirmed to be identical be assigned an identical PTA when calculating genetic evaluations.

Technical Abstract: Consumers are interested in knowing whether cloning and other forms of biotechnology impact food safety, and especially cloning. Cloning by embryo splitting and nuclear transfer was introduced during the 1980s but the performance of clonal families that result from the biotechnology had not been examined. This study documents phenotypic and genetic performance of US Holstein clones from embryo splitting and nuclear transfer for yield and fitness traits. A total of 2319 split embryo clones and 215 nuclear-transfer clones have been registered with the Holstein Association USA. Numbers of embryo-split males clones have decreased as have numbers of nuclear-transfer male clones. For clones to enhance the population genetically, their pedigree merit must be superior to that of the population. Animals selected for cloning were slightly superior genetically to population mean for yield traits. For females, mean superiority of pedigree merit of embryo-split clones compared with that of the population for the same birth year was 186 kg for milk, 9 kg for fat, and 7 kg for protein. For nuclear-transfer clones, superiority to population pedigree merit was 165, 10 and 8 kg, respectively. The advantage for male clones above the population pedigree merit was somewhat greater. The small pedigree advantage for clones of 1 standard deviation above breed mean indicates that the selection of animals to clone was not based primarily on production. Yield deviations of embryo-split clones for milk, fat, and protein were lower than those of their full siblings, which indicates a possible impact of the technology on performance. Yields of nuclear-transfer clones were not significantly different from those of their noncloned full siblings, and were based on small numbers. Those male clones pairs of apparent identical genotype received PTA from daughter yields more similar than did those from same technology that were confirmed by blood typing to be nonidentical. It is recommended those embryo transfer split clones confirmed to be identical be assigned an identical PTA when calculating genetic evaluations.