The purpose of this study was to examine the effect of growing stages of the Korean Native Striped Bull (KNSB) on the freezability and fertility of frozen-thawed semen. First, we investigated the total motility (TM) and progressive motility (PM) according to the diluent used for semen freezing. Second, we examined the effect of the age of KNSB on semen volume, TM and PM of fresh and frozen-thawed semen. Third, we examined the effect of frozen semen from the different age of KNSB on the fertilization rate, and the artificial insemination pregnancy rate. The diluents used in this experiment were Triladyl and Tris-egg yolk extender (EYE). Semen was collected from 5 KNSB in the growing stage (15 months) and 5 adult KNSB (36 months). When Triladyl or Tris-EYE extender was used for semen freezing, there was no difference of the mean TM and the mean PM. However, the mean TM was significantly higher in Bull No. 1885 than Bull No. 4283 ( <0.05). The mean volume of semen collected from the 15-month-old bulls (2.3 ml) was significantly lower ( <0.05) than that from the 36-month-old bulls (5.0 ml). The mean semen concentration was similar for the 15-month-old ( spermatozoa/ml) and 36-month-old ( spermatozoa/ml) bulls. For the 15-month-old and 36-month-old bulls, the mean TM of fresh semen were 93.7% and 88.3%, respectively, and the mean PM were 97.0% and 88.3%, respectively; the 15-month-old bulls showed a particularly high PM ( <0.05). For the 15-month-old and 36-month-old bulls, the mean TM (56.0% and 58.0%, respectively) and the mean PM (64.0% and 70.7%, respectively) of frozen-thawed semen did not differ. The development rates of embryos after fertilization and the pregnancy rate after artificial insemination using frozen-thawed semen did not differ according to the bull's age. In summary, semen volume differed according to the bull's age, but semen concentration and survival rate, the fertilization rate, and the pregnancy rate did not differ according to the stripe bull's age. Accordingly, semen from bulls in the growing stage can be collected and frozen for the preservation and multiplication of rare livestock.

• 박용수(경상북도축산기술연구소)
• 장종식(경북대학교 축산BT학부)