Genetic Advantage of Three Sub-Populations under Genetic Parameters of Realistic Traits and Fluctuated Breeding Objectives

Breeding efficiency was compared among three population schemes; a single population, a population with two sub-populations and a population with three sub-populations when sets of realistics genetic parameters were assumed, and when breeding objectives were changed in the middle of selection program. A simulation experiment of selection was carried out for 10 generations with 20 replications each by comparing average breeding values and inbreeding coefficients among the three population schemes. Genetic gain of growth trait was the largest, then that of meat quality trait was the second largest, and that of reproductive trait was the smallest. The amount of the genetic gain was dependent on their genetic variance. Among the three population schemes, the single population scheme had similar genetic level with the other two schemes under a selection with same economic weights for the traits, however, the multiple sub-populations scheme had the highest genetic level after crossbreeding between sub-populations when inbreeding depression was assumed. The population shceme with three sub-populations can enjoy full advantage of heterosis when different economic weights were applied to the traits. The change of breeding objective made impact on genetic gain of population scheme when different economic weights were applied to the traits, where the population scheme with three sub-populations had higher genetic than the older population schemes.