Assessment of pregnancy in Bergamasca ewes by analysis of plasma progesterone

Abstract

The accuracy of early pregnancy diagnosis, based on blood plasma progesterone concentration 18 days after natural mating (PG18), was studied in 112 Bergamasca ewes. The possibility of improving efficiency of diagnosis by measuring the progesterone concentration on the day of mating (PGM) was also considered. Hormone concentration was determined by solid immunoenzymatic assay (ELISA). Pregnancy diagnosis based on PG 18 was 92% reliable; 100% of ewes having progesterone levels of < 1 ng/ml did not give birth, 95% of those with ⩾ 1.5 ng/ml levels were pregnant, 9% of the flock were between these limits, and half of them lambed. By associating the difference between PG18 and PGM levels with PG18 < 1 ng/ml, the accuracy of pregnancy diagnosis increased significantly ( P < 0.05), as a large number of animals incorrectly judged as positive, due to the erroneous recording of the date of mating, or because of the presence of basal progesterone levels higher than usually found in the breed, could be identified.