Fertility in Ewes Following Controlled Breeding Techniques By D. R. LAMOND* SUMMARY

Groups of Merino ewes were given daily intramuscular injections of IO mg of progesterone for 12-14 days. In one experiment con-ducted during the breeding season, the ewes received pregnant mares ’ serum gonadotrophin (PMS) on the day of the final proges-terone injection and human chorionic gonadotrophin (HCG) 48 hours later, then were inseminated with undiluted semen on the day of the HCG injection. There was a highly significant difference in fertility between two farms. Dosage levels of PMS did not influence results but a significant interaction was observed between farms and dosage of HCG. In a second experiment carried out during the period June to December, which includes the anoestrus period, ewes received PMS on the day of the final progesterone injection and some were placed with rams, while others were given HCG 48 hours later and artifi-cially inseminated. Fertility during June and December was significantly greater than during the intervening months. In addition while fertility following natural service was normal, that following HCG and artificial insemination was extremely low