title: Adjustments on the cryopreservation conditions reduce the incidence of boar ejaculates with poor sperm freezability.
abstract: The objective of the present study was to evaluate the effectiveness of different cryopreservation conditions (CCs) for freezing and thawing boar ejaculates, focusing on those having sub-optimal sperm freezability. Using a split-ejaculate technique, single ejaculates from 53 boars were diluted in lactose-egg yolk extender, containing a final glycerol concentration (GLY) of 2 or 3%, packaged in 0.5 mL straws and were cooled at rates of -10, -40 or -60 degrees C/min (cooling rate: CR). Thereafter, the frozen sperm samples were thawed by warming them at rates of approximately 1200 or approximately 1800 degrees C/min (warming rate: WR). Frozen-thawed sperm samples were assessed for the sperm motility (CASA system) and flow cytometric analysis of plasma and acrosomal membranes integrity. Cooling rate had no influence (P>0.05) on sperm quality parameters, however GLY and WR independently affected (P<0.05) all assessed sperm parameters. Evaluating the combined effect of GLY and WR (four different CCs resulting of a 2 x 2 factorial design), the best post-thaw quality results were achieved for sperm samples frozen with 3% glycerol and thawed at 1800 degrees C/min (CC4). However, there was a significant interaction (P<0.001) between CC and ejaculate for all post-thaw sperm quality assessments. Therefore, ejaculates were classified in three different populations according to the post-thaw sperm quality achieved using control CC (CC1: 2% of glycerol and approximately 1200 degrees C/min of warming). The effectiveness of CCs was different (P<0.05) in the three ejaculate populations. Spermatozoa from ejaculates considered as "good" freezers were relatively unaffected (P>0.05) by the modifications in the CCs, whereas those from "moderate" and, mainly, "bad" freezers were very sensitive (P<0.05). In conclusion, optimization of the CCs - GLY and WR - can improve the cryosurvival of spermatozoa in some ejaculates, particularly in those having poor sperm freezing ability.
authors: Department of Medicine and Animal Surgery, Faculty of Veterinary Science, University of Murcia, E-30.071 Murcia, Spain.
authors: Marta
authors: M
authors: Hernández
authors: Jordi
authors: J
authors: Roca
authors: María A
authors: MA
authors: Gil
authors: Juan M
authors: JM
authors: Vázquez
authors: Emilio A
authors: EA
authors: Martínez
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D002462:Cell Membrane / Q000502:physiology; D015925:Cryopreservation / Q000379:methods / Q000662:veterinary*; D008297:Male; D012662:Semen Preservation / Q000379:methods / Q000662:veterinary*; D013081:Sperm Motility / Q000502:physiology; D013094:Spermatozoa / Q000502:physiology*; D013552:Swine / Q000502:physiology*