FURTHER DEVELOPMENT OF A TRANSCERVICAL TECHNIQUE FOR ARTIFICIAL-INSEMINATION IN SHEEP USING PREVIOUSLY FROZEN-SEMEN

A transcervical technique (the Guelph System for transcervical AI) was used to inseminate 2060 ewes on 65 farms (average 31 ewes, range 5 to 107) in Ontario, Canada, from October 1990 to September 1992, using p reviously frozen semen. Estrus was synchronized using progestagen pess aries and PMSG with median inseminations done at 54 h from pessary rem oval. Maiden ewes were not included. Only ewes in which the cervix cou ld be penetrated were inseminated with 150 million spermatozoa per ins emination. A total of 1809 were penetrated and inseminated (penetratio n rate 87.8%). Success of penetration increased from 76.3% in the firs t 500 ewes to 97.9% in the last 500 (P=0.01). Cervical penetration was more successful in ewes in the accelerated lambing program (92.3%, av erage 3.1 mo since the previous lambing) than those in the annual lamb ing program (82.4%, average 7.0 mo since the previous lambing; P=0.06) . The lambing rate for ewes bred during the combined traditional breed ing seasons (Fall of 1990, 1991, 1992) was 50.7% compared to 24.4% for ewes bred at other periods(P=0.00001). The average time required for handling and insemination decreased from 8.62 min in the first 500 ewe s to 3.62 min in the last 500 ewes. The Guelph System for Transcervica l AI was found to be successful for cervical penetration in most ewes. Penetration success was affected by period since the last lambing and by inseminator experience. The lambing rate was higher for ewes bred during the traditional Fall breeding seasons than during other times o f the year.