ESTIMATION OF THE WEEK OF CONCEPTION IN MERINO EWES USING REAL-TIME ULTRASONIC-IMAGING

Real-time ultrasonic imaging was used to estimate the week of concepti on 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 testoster one-treated wethers. The ewes were scanned 92 days after the introduct ion of the rams to determine litter size, then, based mainly on the si zes of the heads and bodies of the fetuses, the week of conception was estimated. These results were compared with the actual week of concep tion determined from weekly mating and daily lambing records. The week of conception was correctly estimated for 71% of the ewes. The consec utive 2-week period from the start of joining within which conception occurred was correct for 91% of the ewes. The correct half of the join ing period within which conception occurred was diagnosed for 98% of t he ewes.