Sheep breeding program for the year-round production of timed pregnancies for experimental foetal surgery

Foetal lambs of known gestation were supplied to research programs throughout the entire year by controlling the oestrous cycle of the breeding ewes. In about 55 ewes, an average of 70-3 pregnancies of known duration produced an average of 118 lambs for each of the 3 years (168% of lambs to pregnancies). The accuracy of the ram-marking information, plasma radioimmunoassay (18 days after mating) and ultrasonic flow detection (Doppler; 60 days after mating) as indicators of pregnancy is reported for the last 3 years of this program.