Estimation of the week of conception in Merino ewes using real-time ultrasonic imaging

Abstract

Real-time ultrasonic imaging was used to estimate the week of conception in a flock of 4- and 5-year-old Merino ewes. Rams were joined with ewes for 6 weeks after the ewes were 'teased' for 2 weeks by testosterone-treated wethers. The ewes were scanned 92 days after the introduction of the rams to determine litter size, then, based mainly on the sizes of the heads and bodies of the fetuses. the week of conception was estimated. These results were compared with the actual week of conception determined from weekly mating and daily lambing records. The week of conception was correctly estimated for 71% of the ewes. The consecutive 2-week period from the start of joining within which conception occurred was correct for 91% of the ewes. The correct half of the joining period within which conception occurred was diagnosed for 98% of the ewes.