SEASONAL-VARIATIONS IN THE ACTIVITY OF CORPUS-LUTEUM-PERIODICUM ET-GRAVIDITAS OF EWES

Plasma progesterone (P) levels were determined on the 5th, 8th, 14th a nd 16th day of the estrous cycle of nonpregnant and pregnant Tsigai ew es, during the breeding season as well as during anoestrus. Estrus was synchronized using intravaginal pessaires impregnated with 60 mg MAP for 14 days and 600 IU PMSG i/m at the removal of pessaires. P levels were significantly lower (p < 0.05 or p < 0.01) in the ewes during ano estrus, compared to the same category of ewes in the breeding seasons (pregnant/pregnant; nonpregnant/nonpregnant). Differences in the P lev els between pregnant and nonpregnant Tsigai ewes during one seasonal p eriod became apparent at the 16th day postcoitum.