The use and misuse of measurement

摘要

Genetic progress in sheep breeding has come from the recognition of the effects of genes, (both positive and negative), and the incorporation of these genes into the genotype of parent studs, usually by trial and error methods over many years: classical breeding. This process requires measurement to evaluate progress against industry standards. If these measurements contribute to better selection decisions, they may be considered an aid to selection. Some fifty years ago the quantitative genetics school emerged. Their methods for genetic progress rely on the use of additive (positive and negative) genetic variation, and the intensive measurement of production characteristics, principally fleece weight, fibre diameter and liveweight. These characteristics arc seen as contributing most to wool and carcass values - measured performance breeding. Many exponents of this system insist that measurements must always override any subjective judgments - measurement is the basis of selection.