Fertility of Ewes after Intrauterine Insemination with Frozen Semen

In an experiment involving the artificial insemination of 312 Merino ewes, fertilization, early (18 day), and late (100 day) pregnancy rates were examined after intrauterine insemination with frozen semen using a laparoscope. Oestrus was synchronized in ewes by progestagen sponge/PMSG treatment. After cervical insemination of fresh semen (control) 55 hrs after sponge removal, the fertilization, early and late pregnancy rates were 24/30, 37/46 and 33/46 respectively. Following intrauterine insemination of frozen-thawed semen at 24, 36, 48 and 60 hr after sponge removal, fertilized eggs were recovered in 7/27, 12/22, 17/25 and 19/25 ewes; the early pregnancy rates were 13/34, 18/34, 20/34 and 23/35; and the late pregnancy rates were 3/34, 6/34, 17/34 and 19/35 for the respective insemination times.