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RESEARCH ARTICLE
Contents Vol 17(6)

Effects of lamb age, hormone stimulation and response to hormone stimulation on the yield and in vitro developmental competence of prepubertal lamb oocytes

Katherine M. Morton A D , Sally L. Catt B C , W. M. Chis Maxwell A and Gareth 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 Present address: Academic Unit of Paediatrics, Obstetrics and Gynaecology, School of Medicine, University of Leeds, LS2 9NS, UK.

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

Reproduction, Fertility and Development 17(6) 593-601 https://doi.org/10.1071/RD04069
Submitted: 3 July 2004  Accepted: 19 April 2005   Published: 17 June 2005

Abstract

Experiments were conducted to determine the effects of lamb age, hormone stimulation (Experiment 1) and response to stimulation (Experiment 2) on the in vitro production of embryos from prepubertal lambs aged 3–4 and 6–7 weeks of age. For 3–4-week-old lambs, hormone stimulation increased the number of follicles (29.9 ± 15.3 v. 70.6 ± 8.2), oocytes per ovary (18.3 ± 6.3 v. 39.3 ± 5.8) and oocyte development to the blastocyst stage (0/192 (0.0%) v. 115/661 (17.4%); P < 0.05). Lamb age (3–4 v. 6–7 weeks old) increased oocyte development to the blastocyst stage (115/661 (17.4%) v. 120/562 (21.4%) respectively). In Experiment 2, hormone-stimulated lambs (3–4 and 6–7 weeks old) were divided into low, medium or high responders based on the number of ovarian follicles (<20, 20–50 and >100 follicles per ovary respectively). The response to hormone stimulation did not affect oocyte recovery rate, but the number of oocytes suitable for culture was increased for high-responding 3–4-week-old lambs only (P < 0.05). Oocyte development to the blastocyst stage was not affected by response to stimulation for 3–4-week-old lambs (15.2–25.6%; P > 0.05), but was reduced for high (6.7%) compared with low (19.5%) and medium (30.9%) responding 6–7-week-old lambs (P < 0.05). These results demonstrate that the production of embryos from prepubertal lambs is increased by hormone stimulation and lamb age and the response to stimulation does not affect embryo production from 3–4-week-old lambs, although by 6–7 weeks of age a high response to stimulation reduces blastocyst formation.

Extra keywords: embryo development, juvenile.


Acknowledgments

This work was supported by the Australian Research Council. Bioniche Animal Health Australasia and Sydney IVF are thanked for the donation of the eCG, FSH and LH, as well as the media used in the present study. The authors thank Mr S. J. Burgun and the Arthursleigh staff, as well as Mr B. Biffin, for their on-farm assistance and Ms K. J. Heasman, Mr A. P. Souter and Ms R. Bathgate for their technical assistance.


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