MASS SELECTION FOR POST-WEANING GROWTH IN SWINE: I. THE VALUE OF A PEDIGREED CONTROL POPULATION

Abstract

A pedigreed control population of Yorkshire swine has been described. The average size of the breeding population was 20 males and 40 females in each of the seven generations. The effective number of parents per generation was estimated at 87.5. There has been little or no evidence of any significant changes in the genetic value of the population over the seven generations as determined by estimates of additive genetic variance, selection differentials, and other related parameters. The performance of the control population was compared with that of a selected population and with crossbreds produced by mating select population males to control population females. Comparisons were made in the same environments. The comparisons of the effects of the selection program on several traits measured in the two populations have been made, based on the absolute trends in these populations over the seven generations and as a deviation from the performance of the control population.