Abstract
Plasma concentrations of estrogens, gestagens, cortisol (F), 13, 14-dihydro, 15-keto PGF<2αgt; (PGFM) and pregnant mare serum gonadotropin (PMSG) in 10 Thoroughbred mares were measured for a 11-month pregnancy period. Estrone (E1) and estradiol-17β (E2) levels gradually increased as the pregnancy advanced, showing a peak around Month 8 and decreased thereafter. Progesterone (P) levels increased on Months 3 and 11, and 17α-OH-progesterone (17α-OHP)levels peaked on Month 3, whereas 20α-OH-progesterone (20α-OHP) levels increased sharply after Month 6. PGFM indicated peaks on Months 2 and 11. F and PMSG levels peaked on Months 2 and 3. From factor analysis, Month, E1, E2and 20α-OHP were discriminated as Factor 1, increasing with the progress of pregnancy, PMSG, 17α-OHP and P as Factor 2, showing a relation with the secondary corpus luteum, and PGFM and F as Factor 3, affecting PGFM change on Month 2 by F. P also related to both Factors 1 and 3, showing an inverse relation against PGFM. In conclusion E1, E2 and 20α-OHP contained in Factor 1 were suggested to be important especially as parameters of placental function after Month 6.
