COMPARATIVE-STUDIES OF OVARIAN-STEROIDS IN BLOOD, AND SPECIFIC PROTEOLYTIC-ENZYMES IN THE CERVICAL-MUCUS, IN 4 SHEEP BREEDS AFTER ESTRUS SYNCHRONIZATION (PROGESTERONE AND PMSG) .1. BREED VARIATION OF ESTRADIOL-17-BETA AND PROGESTERONE IN BLOOD DURING NATURAL ESTRUS, SYNCHRONIZEDESTRUS, AND THE FIRST ESTRUS AFTER SYNCHRONIZED ESTRUS

The concentrations of oestradiol-17 beta and progesterone in the blood were studied during natural oestrus, synchronized oestrus, and the fi rst oestrus after synchronized oestrus in four sheep breeds (Friesland , Chios, Serres and Karagouniki). During natural oestrus, significant variations of oestradiol-17 beta concentration were only seen in Karag ouniki ewes; during synchronized oestrus, oestradiol-17 beta concentra tion in the blood showed a gradual decrease in all breeds. However, du ring the first oestrus after synchronized oestrus, the concentration o f oestradiol-17 beta in the blood returned to normal in all but the Se rres breed. The concentration of progesterone in the blood showed no v ariation during natural oestrus, but, during synchronized oestrus, sig nificant variations of progesterone in the blood were seen in all but the Serres breed. During the first oestrus after the synchronized oest rus, the progesterone in the blood returned to the natural-oestrus lev els with, however, some differences among the breeds. Oestrous synchro nization therefore disturbed the concentration of oestradiol-17 beta a nd progesterone in the blood of the ewe in a varying way, depending on the breed.