Effect of the holding time at 15 degrees C prior to cryopreservation, the thawing rate and the post-thaw incubation temperature on the boar sperm quality after cryopreservation
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The aim of the present study was to evaluate the effect of the holding time at 15 degrees C prior to cryopreservation (2,4 and 8 h), thawing rate (37 degrees C for 20 s or 70 degrees C for 8 s) and post-thaw incubation temperature (15 degrees C or 37 degrees C) on the post-thaw boar sperm quality. These are important time periods in the freezing-thawing process which have been less studied. Sperm-rich ejaculate fractions from three healthy boars were collected once a week for five consecutive weeks and were cryopreserved with the lactose-egg yolk extender (LEY). Sperm quality was determined by assessing the motility, the acrosome status, and the sperm plasma membrane integrity at 30, 150 and 240 min of incubation. The results show that with the holding time at 15 degrees C prior to cryopreservation there was not a clear effect until at least 24 h of holding time. The thawing rate and the post-thaw incubation temperature, however, had a marked effect on sperm quality. When the samples were thawed at 70 degrees C for 8 s, the sperm viability, motility and some kinetic variables (VCL, VSL, VAP and ALH) were greater than with results observed when the samples were thawed at 37 degrees C for 20 s. In addition after thawing the sperm samples incubated at 15 degrees C had a sustained sperm quality for longer, up to 4 h post-thawing. (C) 2014 Elsevier B.V. All rights reserved.