A general procedure for predicting rates of inbreeding in populations undergoing mass selection

Predictions of rates of inbreeding (Delta F), based on the concept of long- term genetic contributions assuming the infinitesimal model, are developed for populations with discrete or overlapping generations undergoing mass se lection. Phenotypes of individuals are assumed to be recorded prior to repr oductive age and to remain constant over time. The prediction method accoun ts for inheritance of selective advantage both within and between age class es and for changing selection intensities with age. Terms corresponding to previous methods that assume constant selection intensity with age are iden tified. Predictions are accurate (relative errors less than or equal to 8%) , except for cases with extreme selection intensities in females in combina tion with high heritability. With overlapping generations Delta F reaches a maximum when parents are equally distributed over age classes, which is ma inly due to selection of the same individuals in consecutive years. Delta F /year decreases much more slowly compared to Delta F/generation as the numb er of younger individuals increases, whereas the decrease is more similar a s the number of older individuals increases. The minimum Delta F (per year or per generation) is obtained when most parents were in the later age clas ses, which is mainly due to an increased number of parents per generation. With overlapping generations, the relationship between heritability; and De lta F is dependent on the age structure of the population.