title: Factors affecting pregnancy rates following laparoscopic insemination of 28,447 Merino ewes under commercial conditions: a survey.
abstract: The results of laparoscopic insemination of 28,447 Australian Merino ewes with semen from 468 rams were used to study factors influencing pregnancy. The overall pregnancy rate was 71.7% (20,423/28,447). Pregnancy rates varied with type of progestagen implant, type and dosage of PMSG, fresh or frozen semen, wool type and number of ewes inseminated per hour. The pregnancy rate (64.6%) obtained with Medroxy-progesterone acetate (MAP) sponges, was significantly (P < 0.01) lower than with Fluorogestone acetate 30 mg (FGA 30; 74.7%) sponges, Fluorogestone acetate 40 mg (FGA 40; 72.1%) sponges, and Controlled Internal Drug Release (CIDR-G; 71.7%) implants. A PMSG dose of 200 IU resulted in significantly (P < 0.05) lower pregnancy rates (62.4%) compared with 250 IU (72.9%), 300 IU (79.1%) and > or = 375 IU (69.4%). The mean pregnancy rate for ewes administered Folligon PMSG was 71.9%, which was significantly higher (P < 0.001) than that of ewes treated with Pregnecol PMSG (65.8%). The use of Pregnecol PMSG and MAP sponges was associated, and thus their conditional effects could not be calculated. Ewes inseminated with fresh semen were significantly (P < 0.001) more likely to become pregnant (82.2%) than those inseminated with semen frozen in pellets (69.5%) or straws (71.6%). Ewes inseminated during the months of March, April or May (fall, 71.5%) were just as likely to become pregnant as those ewes inseminated in November, December, January or February (69.6%). Significantly (P < 0.05) fewer strong wool ewes become pregnant to laparoscopic AI, (67.6%) than fine (71.7%), fine medium (73%) or medium wool ewes. Significantly (P < 0.0001) more pregnancies (77.6%) were achieved when more than 55 ewes were inseminated per hour compared with fewer than 35 ewes per hour (63.4%).
authors.affiliation: Australian Livestock Genetics, Narromine, NSW, Australia.
authors.forename: J R
authors.initials: JR
authors.lastname: Hill
authors.forename: J A
authors.initials: JA
authors.lastname: Thompson
authors.forename: N R
authors.initials: NR
authors.lastname: Perkins
mesh_terms: D000818:Animals; D001315:Australia; D015925:Cryopreservation; D005260:Female; D006064:Gonadotropins, Equine / Q000008:administration & dosage; D007315:Insemination, Artificial / Q000379:methods / Q000662:veterinary*; D010535:Laparoscopy / Q000662:veterinary; D008297:Male; D010062:Ovulation Induction / Q000379:methods; D011247:Pregnancy; D011270:Pregnancy, Animal; D012661:Semen; D012662:Semen Preservation; D012756:Sheep
chemical_list: D006064:Gonadotropins, Equine