Abstract
A strain development with Landrace pigs was carried out from 1990 to 1996 (for five generations) to improve reproductive ability and the meat performance. The pigs were selected mainly based on EBV of litter size with the BLUP method at 90kg of live weight, and mated atapproximately eight months of age. The mathematical model to analyze the data included the effects of generation and live weight of the females at the time of first mating. The average litter size per generation increased from 9.7 to 10.8 during the experiment. The regression of the litter size was significantly (p<0.05) affected by the weight at first mating, of which the regression coefficient was 0.03 piglet per kilogram of weight. Effect of generation on litter size was not significant. The genetic gain of litter size per generation was 0.14 on the model including generations and was 0.09 on that including both generations and weight of first mating. These results indicate that selection by the BLUP method is feasible for the improvement of the litter size of swine, and that it should be more effective if the body weight at the time of first mating is considered.
