Abstract
Methods were developed to calculate the optimum number of initial unrelated families (equivalent to founders) in a breeding program, which, following selection in a predetermined way, would result in the maximum gain. The required entries were: (1) effective population size (effective family number) after selection, (2) family type (half-sib or full-sib), (3) heritability, (4) number of selections, (5) available resources, and (6) cost per additional family in the initial population. Suggestions of optimum family numbers and other characteristics of the optimum were calculated for particular examples. It seemed important to consider cost components when planning breeding programs. The optimum initial family number was far greater than the intended effective family number when the marginal cost of adding initial families was low. If this cost was high, it was worth investing more than half of any fixed resources in obtaining many families. The value of heritability appeared rather unimportant. For. Sci. 43(2):206-212.