Effect of homologous follicular fluid from medium-sized and large follicles on in vitro maturation of equine cumulus–oocyte complexes
Valéria Amorim Conforti A B , Dirk K. Vanderwall A C and Gordon L. Woods AA Northwest Equine Reproduction Laboratory, Department of Animal and Veterinary Science and Center for Reproductive Biology, University of Idaho, Moscow, ID 83844, USA.
B Present address: Department of Animal Sciences, Washington State University, Pullman, WA 99164, USA.
C Corresponding author. Email: dirkv@uidaho.edu
Reproduction, Fertility and Development 17(6) 651-658 https://doi.org/10.1071/RD05036
Submitted: 29 March 2005 Accepted: 12 June 2005 Published: 29 July 2005
Abstract
The in vitro maturation (IVM) of equine oocytes is typically performed using various synthetic media; however, an optimal IVM system for equine oocytes has not been developed. The aim of the present study was to evaluate the effects of two types of follicular fluid (FF) obtained from cyclic mares and two incubation intervals for the IVM of equine cumulus–oocyte complexes (COCs). Follicular fluid was collected from medium-sized (20–29 mm diameter) and large (≥30 mm; post-human chorionic gonadotrophin administration) follicles using transvaginal ultrasound-guided follicle aspiration. Compact (n = 232) and non-compact (n = 183) COCs obtained from a slaughterhouse were incubated separately in the following groups: (1) FF from medium follicles for 24 h; (2) FF from large follicles for 24 h; (3) control (synthetic) medium for 24 h; (4) FF from medium follicles for 24 h then FF from large follicles for an additional 24 h; (5) FF from large follicles for 48 h; and (6) control medium for 48 h. For compact COCs, there was a tendency (P = 0.06) for more COCs incubated in FF from large follicles for 24 h to reach metaphase II compared with those incubated in control medium for 24 h (58% v. 35%, respectively). More (P < 0.05) compact COCs had degenerated after incubation in control medium for 48 h compared with all other groups (51% v. 14–24%, respectively). For non-compact COCs, incubation in FF from medium follicles for 24 h resulted in more (P = 0.05) COCs at metaphase II compared with control medium for 48 h (58% v. 29%, respectively). These results indicate that homologous FF from cyclic mares is a suitable alternative for the IVM of equine COCs and that it may be superior to conventional media for longer (i.e. >24 h) incubation intervals.
Extra keywords: cumulus expansion, horse, nuclear maturation, ooplasm.
Acknowledgments
The authors are especially grateful to Juanita Sosa of the Center for Reproductive Biology for assistance with sample collection, Ann Norton of the Washington, Wyoming, Alaska, Montana, Idaho Medical Education Program at the University of Idaho for technical support with the confocal microscopy and Dr Chris Williams of the Department of Statistics at the University of Idaho for helpful advice on data analysis. The authors also thank J. Adams, J. Burnett, M. Comer, M. Dredge, T. Gable, L. Hartt, G. Huff, K. Hyde, E. Kimble, K. Shawcroft and J. Steele for valuable assistance. This study was supported by the Idaho Equine Education Bill and private donations.
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