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A method is presented for evaluating industry breeding schemes for Australian beef cattle. Multitrait selection is considered. The criteria of evaluation are the annual genetic gains in the breeding objective and its component traits, and the net present value of the return from investment in the scheme. The main methods employed by the PC computer program ZPLAN, developed to facilitate such evaluations, are described and are applied to an example population. A deterministic approach is taken to the prediction of annual genetic gain. Various selection groups are defined in the population, each with particular information sources for index selection, and allowing also for two-stage selection. Gene flow methods are applied to assess the discounted return from investment in one round of selection over a defined investment period. The associated fixed and variable costs are calculated, and used to derive the net present value, or profit, from the selection. An example population with a breeding unit of 10000 cows, supplying bulls to a total population of 200000 cows, is envisaged. Seventy percent of the cows in commercial herds are assumed to be mated by bulls derived from the breeding unit. Genetic and biological/technical parameters required by the program are presented. Criteria considered to be available for use in selection are weights at birth and at 200, 400 and 600 days of age. Results are given for individual selection groups and for the whole population. The annual genetic response in the breeding objective ($1.43) comprised $2.21 gain in growth traits (sale weight direct and maternal), $0.37 gain in reproduction traits (cow survival and weaning rates and bull fertility), $0.06 loss in carcass traits (dressing and saleable meat percentages and fat depth), a $1.00 increase in the cost of maintaining cows and a $0.09 loss for increased calving difficulty. The return, cost and profit per cow in the population from one round of genetic selection using the available growth measures was $8.14, $1.34 and $6.81, respectively.

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Summary In the development of applied quantitative genetics to date it was assumed that natural selection was absent. Hence, an important part of the environment has been ignored and breeders have concentrated on estimated breeding values. The same is implicit in molecular efforts to modify genotypes of animals directly. Furthermore, explanations of evolution imply that genes are responsible for evolutionary changes. These consequences of this assumption are now seen to be wrong. Beilharz (1998b) shows that the resources available in any environment limit the phenotypes that can develop there. This is because natural selection is always acting on phenotypes and has already selected organisms to be as good as it is possible to be on the available resources. This paper describes the necessary theoretical changes to quantitative genetics and the consequences that follow for evolutionary theory and animal breeding. A component of environment (Er, regional environment) describing that environmental variation to which natural selection adapts populations of organisms, is introduced. Variation among levels of Er reflects different amounts of resources available for animals to live on. At each level of Er genotypes are selected that have maximum phenotypic fitness exactly at that level, at the expense of genotypes with either lower fitness or a fitness demanding higher levels of resources to realise its potential. Changing environments (levels of resources) favour new phenotypes whose resource demand matches the changed resources available. The role of genes is to produce those variants that have phenotypes able to follow the environmental change. The paper also shows how genotype–environment interactions have resulted from the matching of genotypes to different levels of Er in earlier times. In the breeding of domestic animals, genetic improvement of production traits, without raising Er, must be accompanied by trade‐offs (antagonisms) among production traits and with fitness. To obtain improvement with minimal negative side effects, breeding goals must be specified more comprehensively that to date, e.g. by also taking into account the duration of productive life. The selection criteria and estimates of heritability and genetic correlations used in the estimation of breeding values must be appropriate for the particular level of environment in which the genetic improvement is to be made. Zusammenfassung Das fehlende E: Die Rolle der Umwelt in Evolution und Tierzucht Die bisherige Entwicklung der quantitativen Genetik fand unter Ausklammerung der natürlichen Selektion statt. Das führte zur Vernachlässigung eines wichtigen Teils der Umwelteffekte und die Züchter konzentrierten sich auf geschätzte Zuchtwerte. Das Gleiche gilt für die Bemühungen, Genotypen durch molekulargenetische Methoden zu manipulieren. Ausserdem basieren Interpretationen der Evolution darauf, daß Gene für evolutionäre Veränderungen verantwortlich sind. Diese Konsequenzen der Auskalmmerung der natürlichen Selektion sind jetzt als falsch erkannt worden....