Topics to be confronted in development of industry structures to facilitate and evaluate genetic change include the nature and extent of genotype by environment interactions (GEI), development of coherent procedures for simultaneous within- and across breed selection, the role of cooperative group breeding schemes, and the potential impact of elite nucleus herds propagated using advanced reproductive technologies. GEI can lead to subdivision of populations, but will more likely place a premium on use of multiple-trait analyses or testing in multiple herds to accommodate GEI
 involving fixed and random environments, respectively. Joint within- and
 across-breed selection requires information on breed and heterosis parameters, within-breed genetic evaluations and genetic trends and would be facilitated by
 greater use of crossbred data in national evaluation programs. Nucleus breeding schemes may accelerate rates of genetic improvement, but must acommodate retention of genetic variation sufficient to allow adaptation to changing environments and selection objectives.

D. R Notter, W. D Hohenboken

Proceedings of the World Congress on Genetics Applied to Livestock Production, Volume XV. Beef cattle, sheep and pig genetics and breeding, fibre, fur and meat quality., , 347–356, 1990
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