Pregnancy diagnosis and assessment of fetal numbers in the ewe in a commercial setting

Abstract

Jugular plasma progesterone concentrations were used to accurately predict open ewes (96 ± 3%) in early pregnancy, but they less accurately predicted subsequent lambing especially during the late breeding season and most of the seasonal anestrus. Progesterone values clearly indicated that 500 I.U. of P.M.S.G. elevated ovulation rate in synchronized ewes, but did not clearly indicate fetal numbers. During late pregnancy (88–108 days), abdominal palpation, doplar ultrasound and serum progesterone analysis were equally efficacious in predicting lambing (86 ± 9.8%, 90 ± 9.0% and 87 ± 4.1%, respectively), but a high percentage of ewes lambed that were diagnosed as nonpregnant (30 ± 15.0%, 48 ± 17.3% and 25 ± 8.4%, respectively). Accuracy of the serum progesterone test improved the later the test was performed, although considerable individual overlap existed. Progesterone values for ewes bearing 1, 2, or greater than 2 fetuses at 94 to 95 days of gestation differed (5.5 ± 0.3, 8.0 ± 0.4 and 12.4 ± 2.1, respectively (P < 0.05), whereas at 103 to 108 days values for ewes carrying two or more fetuses did not differ.