Seasonal influences on blood plasma progesterone concentration in ewes of Black held Mutton sheep breed (short communication)

In 71 Black head mutton sheeps on pasturing and housing were determined fro m the year 1995 to 1997 and there in the period from March to October the c oncentration of blood progesterone for determination of onset of estrus. Th e level of blood progesterone reported, on literature also, no cycle on thi s period. The investigation of 6 of this sheeps with ultrasonography had th e result of ovarian activity with follicles from 2 mm to 7 mm in diameter, but no cycle was determined. The progesterone level of minimum and maximum on all years differed from Ma rch to beginning of September between 0,33 ng/ml and 2,15 ng/ml blood proge sterone, after this to October between 0,82 ng/ml and 4,25 ng/ml blood prog esterone. The pregnant sheeps detected blood progesterone concentrations from 5,50 ng /ml to 13,55 ng/ml blood progesterone (twins). The corpus luteum activity m ay be is prevalent on the blood progesterone level up 2 ng/ml and pregnancy up 5 ng/ml blood progesterone. The detectability of blood progesterone and supplemented ultrasonography of ovary possess the possibility recording of onset cycle activity and early pregnancy diagnosis.