title: An efficient method of ovarian stimulation and in vitro embryo production from prepubertal lambs.
abstract: The production of embryos from prepubertal lambs is inefficient, partly resulting from the low developmental competence of prepubertal lamb oocytes, and partly because a high proportion of lambs fail to respond to hormone stimulation. The development of a hormone stimulation regimen that all lambs respond to would increase the efficiency of breeding from prepubertal animals. Using a hormone stimulation regimen consisting of oestradiol benzoate (50 microg), a norgestomet implant (1.5 mg), pregnant mare serum gonadotrophin (400 IU) and follicle stimulating hormone (130 mg) all lambs (n = 19) responded to hormone stimulation. Uterine and ovarian weight ranged from 2.8 to 7.2 g (11.8 +/- 0.7 g) and from 1.7 to 54.1 (12.5 +/- 2.9 g), respectively. The number of ovarian follicles and oocytes recovered ranged from 20.0 to 500.0 (118.2 +/- 29.2) and from 13.0 to 455.0 (82.0 +/- 24.2), respectively, and oocytes suitable for in vitro production were obtained from all 19 lambs. Uterine weight was related to both bodyweight and growth rate (P < 0.05), although ovarian weight and the number of ovarian follicles were not related to either bodyweight or growth rate. Oocyte cleavage varied between hormone-stimulated lambs (0.0-93.0%; P < 0.05), and 484/775 (62.2%) of the oocytes cultured cleaved. Oocytes from 17 of the 19 lambs (89.5%) developed to the blastocyst stage in vitro , and the proportion of zygotes forming a blastocyst (by Day 7) ranged from 0.0 to 66.7% for individual lambs. Overall, 33.9% of zygotes (n = 164) developed to the blastocyst stage, producing 8.6 +/- 2.8 blastocysts per lamb.
authors.affiliation: Centre for Advanced Technologies in Animal Genetics and Reproduction (ReproGen), Faculty of Veterinary Science, The University of Sydney, Australia. kmorton@vetsci.usyd.edu.au
authors.forename: K M
authors.initials: KM
authors.lastname: Morton
authors.forename: S L
authors.initials: SL
authors.lastname: Catt
authors.forename: W M C
authors.initials: WM
authors.lastname: Maxwell
authors.forename: G
authors.initials: G
authors.lastname: Evans
mesh_terms: D000818:Animals; D001947:Breeding / Q000379:methods*; D047108:Embryonic Development / Q000502:physiology; D004958:Estradiol / Q000031:analogs & derivatives / Q000494:pharmacology; D005260:Female; D005307:Fertilization in Vitro / Q000379:methods / Q000662:veterinary*; D005640:Follicle Stimulating Hormone / Q000494:pharmacology; D006064:Gonadotropins, Equine / Q000494:pharmacology; D066298:In Vitro Techniques; D009865:Oocytes / Q000254:growth & development; D009929:Organ Size; D010062:Ovulation Induction / Q000379:methods* / Q000662:veterinary*; D011282:Pregnenediones / Q000494:pharmacology; D012756:Sheep; D014599:Uterus / Q000502:physiology
chemical_list: D006064:Gonadotropins, Equine; D011282:Pregnenediones; C074283:estradiol 3-benzoate; C100284:norgestomet; D004958:Estradiol; D005640:Follicle Stimulating Hormone