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RESEARCH ARTICLE
Contents Vol 17(7)

An efficient method of ovarian stimulation and in vitro embryo production from prepubertal lambs

K. M. Morton A C , S. L. Catt B , W. M. C. Maxwell A and G. Evans A
+ Author Affiliations
- Author Affiliations

A Centre for Advanced Technologies in Animal Genetics and Reproduction (ReproGen), Faculty of Veterinary Science, The University of Sydney, NSW 2006, Australia.

B Sydney IVF, 4 O’Connell Street, Sydney, NSW 2000, Australia.

C Corresponding author. Email: kmorton@vetsci.usyd.edu.au

Reproduction, Fertility and Development 17(7) 701-706 https://doi.org/10.1071/RD04105
Submitted: 29 September 2004  Accepted: 10 July 2005   Published: 27 September 2005

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 µg), 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.

Extra keywords: embryo, juvenile, oocyte, superovulation.


Acknowledgments

This work was supported by the Australian Research Council. Bioniche Animal Health Australasia is thanked for donation of the PMSG, FSH and luteinising hormone, and Sydney IVF for the media used in this study. The authors wish to thank Dr P. Thompson for statistical advice and Mr S. J. Burgun and the Arthursleigh staff for their on-farm assistance, and Ms K. J. Heasman, Mr A. P. Souter and Dr R. Bathgate for their technical assistance.


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