Genetic improvement of farm animal requires that objectives be defined clearly for specific production resources. The objectives could be to change the physiological function to fitting low cost of production or to gain benefits from genetic and environmental changes. Strategies to meet the objectives could be: 1) selection among existing populations, 2) direct selection when suitable populations are chosen and objectives are properly defined, 3) hybridization when traits show heterosis or progress is slow, or 4) creation of biologically diverse lines. Merits of new genetic material must be evaluated in environments for which it will be adapted. The physiological functions should be understood for the characteristics we wish to change but can not be measured at young ages, in live animals or in both sexes. The production systems should be evaluated in terms of integrated production efficiency to derive meaningful progress.