Early Pregnancy Diagnosis Based upon Plasma Progesterone Levels in the Cow and Ewe

Abstract

The concentration of progesterone in peripheral plasma was determined in cows 19 to 22 days after insemination, and in ewes 16 to 21 days or 32 to 35 days after mating, using a competitive protein binding radio-assay. A level exceeding 2.5 ng/ml in cows, or 1.5 ng/ml in ewes, in a single plasma sample taken during the periods specified, was taken as indicative of pregnancy. The accuracy of this diagnosis was assessed by rectal palpation 6 to 7 weeks after insemination in cows, and by lambing records in the ewes. All negative diagnoses in cows (12) and ewes (21) proved correct. Of 13 positive laboratory diagnoses of pregnancy in cows, 11 (85%) were confirmed by rectal palpation. Twenty-seven of 29 ewes (93%) classed as pregnant on Days 16 to 21 did lamb. The discrepancies between laboratory and field diagnoses observed in both species are probably attributable to embryonic mortality. Twelve ewes classed as pregnant during the Day 32 to 35 sampling period all lambed. Copyright © 1973. American Society of Animal Science. Copyright 1973 by American Society of Animal Science