Aspects of breeding objectives and selection criteria are reviewed, with particular reference to how scientific principles can be used to ensure that the outcome best meets the perceptions and needs of the users while remaining as close as possibleto the technical economic optimum. Alternative methods of presenting and delivering selection indexes, such as index expression, index formulation, focusing on the response to selection rather than on index weightings, construction of component indexes and the use of direct accounting for costs of constraints rather than rescaling methods, can all help in improving the acceptance of an index. Development and implementation of selection criteria also involve consideration of the selective mating decisions that form an integral part of selection decisions in the field. The technical basis of factors that foster emphasis on individual mating decisions in the field are discussed in relation to formulation of the breeding goal and selection index and in relation to non-linear economic and genetic parameters. Strategies that focus on the use of a linear index for the selection of sires and dams followed by selective mating of selected parents have the greatest potential for implementation in the industry. Examples are taken from the Canadian dairy industry, but principles apply generally.
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