Abstract :
Fifty Corriedale ewes were used in this study to evaluate pregnancy diagnosis in sheep.
Ewes were bred under a pen mating system and pregnancy diagnosis was initiated from day
15 post-mating, applying the diagnostic techniques of trans-abdominal real-time B-mode
ultrasonography, Preg-alert (A-mode ultrasonography), the Doppler ultrasonic fetal pulse
detector or the plasma progesterone concentration assay (EIA). These tests were repeated
fortnightly on all the ewes until the onset of lambing. The accuracy of trans-abdominal realtime
B-mode ultrasonography (68%) at days 15–30 of pregnancy increased to 100% by days
61–75 and remained constant until lambing. The accuracy of the Preg-alert (56%) diagnosis
at days 31–45 increased to 94% by days 91–105 of gestation and then decreased to 82% from
days 136 of gestation to lambing. The accuracy of both the Doppler ultrasound (56%) at days
31–45 and plasma progesterone assay (98%) at days 15–30 of gestation increased to 100% at
days 76–90 and 46–60 of gestation, respectively and remained constant until parturition.
The mean plasma progesterone concentration at days 0–6 (1.41±0.21 ng/ml) increased to
4.0±0.87 ng/ml at days 16–30 (days 18.23±0.78) post-mating. Animals returning to estrus
recorded less than 1 ng/ml at days 18.23±0.78 post-mating. The accuracy of both the Bmode
ultrasonic technique (78%) and plasma progesterone assay (98%) was significantly
higher (P < 0.05) than the accuracy obtained with the A-mode and Doppler ultrasound (both
56%) at days 31–45 of gestation. The study concluded that real-time B-mode ultrasonography
is the earliest, most accurate, safest, fastest and most economical method of pregnancy
diagnosis in sheep at farm level. The A-mode and Doppler methods can also be used under
field conditions, where sophisticated laboratory facilities are not available. Plasma progesterone
assays (EIA) can be used as a means of early pregnancy diagnosis in organized sheep
farms with fair accuracy.
