Synchronized breeding of cycling ewes to produce fetuses of known gestational age.

A treatment regime involving a subcutaneous ear implant containing 3 mg of 17 alpha-acetoxy-11 beta-methyl-19-nor-preg-4-ene-3,20,dione (norgestomet) accompanied by an intramuscular injection of 1.5 mg norgestomet and 0.5 mg estradiol valerate proved effective for synchronizing estrus in the cycling ewe. Pregnancy rates were equivalent to those of control ewes mated concurrently. Sixty-two percent of all treated ewes became pregnant at the synchronized estrus. The initiation of the treatment regime was scheduled to allow delivery of fetuses of a specified age on the date requested by the investigator.