The infinite population and finite loci genetic model was used to investigate the change in favorable allele frequency of quantitative trait loci (QTLs) during long-term selection in pigs. All QTLs were considered to be additive. Two different heritabilities (0.2 and 0.5), two different favorable allele frequencies of major loci (0.01 and 0.50), and various genotypic values of QTL were assumed in the base population. Two different number of loci (40 and 80) and a selection rate of 75% were used in the simulation. The favorable allele frequency increased more rapidly for major genes than for polygene during selection. Higher heritability, smaller number of loci, and larger effect of major genes accelerate the fixation of favorable allele of major genes. In conclusion, most of the major alleles seem to be fixed if the trait including major genes is selected for a long-term.

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The present study was carried out to develop devices which permit to collect and wash porcine cumulus-oocyte complexes (COCs), effectively. In collecting device, follicles are disrupted by needles and COCs are released into culture medium by vibration. Washing device consists of two strainers above and below given sizes by which particles are removed from a fluid.
Collection of porcine COCs
By the use of collecting device, the number of COCs collected per 1 min increased significantly compared with the conventional methods. Collecting methods did not influence the quality (rank) of COCs. In COCs classified as rank A, their abilities of maturation and development after culture did not differ among the collecting methods.
Washing porcine COCs
The mean values (±SD) of major and minor axis in COCs were 226.7 (±86.1) and 194.5 (±56.6) μm, respectively. On the basis of the data, subsequent experiment was carried out to determine the optimal size of meshes for two strainers. Percentage of COCs passed through 300×300μm mesh in the inner cylinder (strainer I) was 99.6%, and that trapped with 100×100μm mesh in the outer cylinder (strainer II) was 99.9%. By the use of washing device, the volume of washing medium could be reduced 2/3 and the time required for washing was shorter to 1/2 compared with the conventional method.
The results indicate that efficacy of collecting and washing COCs are remarkably improved by these devices without influencing the qualities of porcine COCs.

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