Studies on the improvement of reproductive efficiency in Korean native cows -Plasma progesterone concentrations for monitoring ovarian activity in the postpartum period-

한우(韓牛)의 번식효율(繁殖效率) 증진(增進)에 관한 연구(硏究) -혈중(血中) progesterone농도(濃度) 측정(測定)에 의한 분만(分娩)후 난소기능(卵巢機能) 회복상태(回復狀態)의 검토(檢討)-

Plasma progesterone concentrations in 44 suckling Korean native cows were determined to monitor ovarian activity postpartum by radioimmunoassay. Blood samples were collected in 3 day intervals from 15 to 80 days postpartum. The ovaries and uterus were examined in 6 day intervals by rectal palpation. Results are summaried as follows: 1. The cows were qualified into four categories; Type I(normal): cyclic changes in plasma progesterone concentrations appear within 45 days postpartum(35 cows, 79.5%), Type II(cycle delayed): delayed resumption of ovarian activity by 55 days postpartum(5 cows, 11. 4%), Type III(cycle ceased with low progesterone): plasma progesterone concentrations remained low(${\leq}1ng/ml$) until 80 days postpartum(3 cows, 6.8%), Type IV(cycle ceased with high progesterone): plasma progesterone concentrations after 30 days remained high(${\geq}4.0ng/ml$) until 80 days postpartum(1 cow, 2.3%). 2. Out of the cows classified Type II and III, 7 cows had inactive ovaries and a cow had follicular cyst by rectal palpation. The cow of Type IV was diagnosed as bearing persistent corpus luteum by rectal palpation. 3. About 82% of the cows showed significant rises in plasma progesterone concentrations prior to 50 days postpartum and the cows of Type II and III resumed cycles in 31. 6(range 17~55) days after calving. However, 43.2% resumed cycles in 50 days postpartum by estrus signs. These results indicated that plasma progesterone concentrations assessed by radioimmunoassay can be utilized for monitoring postpartum ovarian activity and would be helpful for the early detection of ovarian dysfunction in the Korean native cow.