Slow cooling prevents cold-induced damage to sperm motility and acrosomal integrity in the black-footed ferret (Mustela nigripes)
R. M. Santymire A D E F , P. E. Marinari B , J. S. Kreeger B , D. E. Wildt A and J. G. Howard CA Department of Reproductive Sciences, Conservation & Research Centre, Smithsonian’s National Zoological Park, Front Royal, VA 22630, USA.
B US Fish & Wildlife Service, National Black-Footed Ferret Conservation Centre, Wellington, CO 80549, USA.
C Department of Reproductive Sciences, Smithsonian’s National Zoological Park, Washington, DC 20008, USA.
D Department of Environment Science and Policy, George Mason University, Fairfax, VA 22030, USA.
E Present address: Department of Conservation & Science, Lincoln Park Zoo, Chicago, IL 60614, USA.
F Corresponding author. Email: rsantymire@lpzoo.org
Reproduction, Fertility and Development 19(5) 652-663 https://doi.org/10.1071/RD06096
Submitted: 10 July 2006 Accepted: 26 March 2007 Published: 1 June 2007
Abstract
The endangered black-footed ferret (Mustela nigripes) has benefited from artificial insemination; however, improved sperm cryopreservation protocols are still needed. The present study focused on identifying factors influencing gamete survival during processing before cryopreservation, including: (1) the presence or absence of seminal plasma; (2) temperature (25°C v. 37°C); (3) type of medium (Ham’s F10 medium v. TEST yolk buffer [TYB]); (4) cooling rate (slow, rapid and ultra-rapid); and (5) the presence or absence of glycerol. Seminal plasma did not compromise (P > 0.05) sperm motility or acrosomal integrity. Sperm motility traits were maintained longer (P < 0.05) at 25°C than at 37°C in Ham’s or TYB, but temperature did not affect (P > 0.05) acrosomal integrity. Overall, TYB maintained optimal (P < 0.05) sperm motility compared with Ham’s medium, but Ham’s medium maintained more (P < 0.05) intact acrosomes than TYB. Slow cooling (0.2°C min–1) was optimal (P < 0.05) compared to rapid cooling (1°C min–1), and ultra-rapid cooling (9°C min–1) was found to be highly detrimental (P < 0.05). Results obtained in TYB with 0% or 4% glycerol were comparable (P > 0.05), indicating that 4% glycerol was non-toxic to ferret sperm; however, glycerol failed to ameliorate the detrimental effects of either rapid or ultra-rapid cooling. The results of the present study demonstrate that the damage observed to black-footed ferret spermatozoa is derived largely from the rate of cooling.
Additional keywords: assisted reproduction, conservation, genome resource banking, mustelid.
Acknowledgements
The authors thank Dr Mitchell Bush for veterinary care, Lisa Ware for veterinary technical support and the animal care staff of the US Fish and Wildlife Service-National Black-Footed Ferret Conservation Centre and the National Zoological Park’s Conservation & Research Centre for valuable assistance. The authors are especially grateful to Lena May Bush, Linwood Williamson, Lawrence Layman, Robb Santymire and Bobby Rodden for dedicated assistance. This research was supported by the Nelson Endowment Fund and Friends of the National Zoo.
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