Plasma progesterone concentrations were measured from 97 Che-ju native mares throughout the estrous cycle, Day 20 to 23, 5 to7 months of pregnancy, and gestation period ( l to 7 months) using the radioimmunoassay techniques for pregnancy diagnosis.
Plasma progesterone concentrations during the estrous cycle were the lowest (<[1.0ng㎖) at estrus, remained high from 9 to 18 days (3.7∼7.6ng/㎖) and drastically decreased thereafter to reach minimal concentrations at the next estrus. Plasma progesterone concentrations at Day 21 to 24 were a significantly different between in pregnant mares (>5.7ng/㎖l) and in non-pregnant mares (<1.0ng/㎖).
The accuracy of the pregnancy diagnosis based on plasma progesterone concentrations at Day 20 to 23 was 86.7% for positive and 100% for negative, whereas on 5 to 7 months was 66.7% for positive and 71.0% for negative, respectively.
Plasma progesterone concentrations during the gestation period(1 to 7 months) increased after 1 month of pregnancy, with peak concentrations(>8.0ng/㎖) occurring between 60 to 100 days of pregnancy, and decreased below 1.7ng/㎖ after 6 months of pregnancy.
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