Studies on the improvement of reproductive efficiency in Korean native cows -The use of plasma progesterone concentrations for early pregnancy diagnosis-

한우(韓牛)의 번식효율(繁殖效率) 증진(增進)에 관한 연구(硏究) -Progesterone농도(濃度) 측정(測定)에 의한 조기임신진단(早期姙娠診斷)-

Plasma progesterone concentrations were measured in 24 Korean native cows by a radioimmunoassay at 0, 6 and 20 days after insemination. As a result, 23 cows (95.8%) were judged to be in estrus with ovulation and one cow (4.2%) was judged to be in estrus without ovulation. Plasma progesterone concentrations at 20 days after insemination were $5.11{\pm}1.33$ (mean${\pm}$SD, range 3.20~7.86) ng/ml in pregnant cows and $0.35{\pm}0.10$ (range 0.30~0.50) ng/ml in nonpregnant cows. Of the 20 cows, 18 cows were confirmed the pregnant by rectal palpation at 60 days after insemination. The accuracy of the pregnancy diagnosis based on plasma progesterone concentration was 90 % for positive case and 100% for negative case.