A total 2,488 ejaculates during 4 years from 80 Korean native bulls over the age from 3 to 12 years of bull herds of Artificial Breeding Center, National Livestock Federatives Cooperation were collected and analyzed to study the effects of collection year, age of bulls, month of years, collection interval and ejaculation frequency per day on semen volume, sperm concentration, total sperm per ejaculate and sperm motility. 1. Semen volume, sperm concentration, total sperm per ejaculate and sperm motility index for the all ejaculates using least squares procedure averaged 5.73ml, 9.133${\times}$108/ml, 52.527${\times}$108 and 62.81, respectively. 2. Semen volume varied significantly with collection year, collection interval and ejaculation frequency per day(P<0.01), but effects of age of bulls and month of years on semen volume were not significant. Eight to 15 days collection interval showed the highest volume, and 1st ejaculate contained 5.6% more volume than 2nd ejaculate. 3. There were significant differences among collection years, months of years and ejeculation frequencies per day except collection intervals in sperm concentration per ml(P<0.05, P<0.01). Six to 8-year-old bulls was the highest concentration. Higher sperm concentration per ml was in April to July and lower month was October and December. Sperm concentration in 2nd ejaculate was higher than in 1st ejaculate. 4. Total sperm per ejaculate affected by all environmental factors studied(P<0.05, P<0.01). Age of bulls, collection interval and ejaculation frequency per day showed the highest total sperm was 6 to 8-year-old bulls, 8 to 15 days interval and 1st ejaculate, respectively. Higher total sperm per ejaculate was in April to July and lower total sperm was in September to December. 5. In sperm motility, there were significant differences among collection years, ages of bulls and collection intervals except months of years and ejaculation frequencies (P<0.01). Higher sperm motility was in 6 to 12-year-old bulls and in 5 to 7 days collection interval.

This experiment was carried out with the purpose to get some information about the properties of Simmental bull semen during summer season. The results obtained were summarized as follows: 1. Semen volume per ejaculation, sperm concentration and sperm viability were averaged 5.16ml, 6.6billion and 65%, respectively. 2. Percentage of motile sperm after dilution in skmmilk solution and trisbuffer for 5 days were 34.16% and 35.0%, respectively. 3. Viability of spermatozoa frozen in skimmilk extender and trisbuffer for 5 days were 20. 83% and 25.66%, respectively. 4. Percentage of live sperm, MRT and pH value were 71.8∼72.1%, 8.40∼8.21 minutes and 6.78, respectively. 5. Diluted semen showed strong resistance to the cold shock than that of fresh semen. 6. Rscovery of sperm motility after freezing for 24 hours was relatively weak.

This experiment was conducted to investigate the effects of temperature and time of sedimentation and dilutor on the a, pp.arance of B-body in top and bottom fractions at separation of X and Y- chromosome bearing spermatozoa in boar semen. 1. The top fraction showed higher a, pp.arence rate of B-body than the bottom. 2. Sixty minutes at 5 and 15$^{\circ}C$ and 90 min, at 25$^{\circ}C$ showed highest difference of B-body a, pp.arence rate between top and bottom fractions. The highest difference was shown in the treatments of Sg at 5$^{\circ}C$, C at 15$^{\circ}C$ and P at 25$^{\circ}C$. 3. The highest difference was shown in the treatments of 25$^{\circ}C$ and Sg for 30 min, 15$^{\circ}C$ and P for 60 min. and 25$^{\circ}C$ and P for 90 min. 4. Sixty minutes in C, P, S and Sg dilutors showed the highest difference. 5. 25$^{\circ}C$ of the temperature levels, 60 min of the time levels and P of the dilutor levels showed the highest difference. 6. The difference was given due to the individual boar.

The sows which had not returned estrus since 15 to 152 days after weaning were treated with PMSG or PGF2$\alpha$ to induce estrus and inseminated to conceive on that estrus. 1. Eight (83%) among 12 sows treated with PMSG came into estrus on average 5.3 days after treatment. 2. The one sow which didn't show any estrus by treatment of PMSG showed an estrus by intramuscular use of 10mg PGF2$\alpha$ and the other one showed an estrus by another intramuscular use of 1000 I.U. of PMSG at 15 days after first injection of PMSG. 3. The one sow injected with Vit. A.D.E. complex(Injacom) (Vit. A 500,000 I.U., Vit. D. 75,000 I.U., and Vit. E. 50 I.U. per ml) on 6 days before PMSG injection showed an estrus on 6 days after PMSG injection and farrowed 8 piglets. 4. Five among 10 sows showed an estrus by treatment of PMSG or PGF2$\alpha$ were pregnant and litter size of the four farrowed sows averaged 9.5.