The aim of this study was to compare the effect of ethylene glycol versus glycerol for dog semen freezing, on post-thaw longevity, motility and motility parameters, and on plasma membrane functional integrity. Semen was diluted in two steps with an egg yolk TRIS extender containing a final concentration of either 5% glycerol or 5% ethylene glycol, and frozen in 0.5 ml straws, with 100 106 spermatozoa/ml, over nitrogen vapours. Semen motility was evaluated both under a light microscope and with a Computer Assisted Motility Analyser System, immediately after thawing and then hourly till 4 h of incubation. Sperm membrane functional integrity was assessed with the hypoosmotic swelling test (60 mOsm fructose solution) applied at thawing and then hourly, for 4 h, on incubated samples. Motility (light microscope) and total and progressive motility (analyser) were significantly higher in ethylene glycol frozen samples at thawing (P < 0.01); from hour 1 onwards the effect of the cryoprotectant became not significant. Semen frozen with ethylene glycol showed higher path velocity and higher straight line velocity till 3 h after thawing; however, ethylene glycol semen samples also showed higher curvilinear velocity and higher lateral head displacement, which may indicate a capacitation-like condition affecting sperm membranes and possibly reducing post-thaw longevity. Functional integrity of plasma membrane was similar in glycerol and ethylene glycol samples till 3 h after thawing, then ethylene glycol samples showed a higher decline. The strong though short-lived positive effect of ethylene glycol is worth being evaluated further.
Comparison between glycerol and ethylene glycol for dog semen cryopreservation
MILANI, CHIARA;MARTINI, MARCO
2006
Abstract
The aim of this study was to compare the effect of ethylene glycol versus glycerol for dog semen freezing, on post-thaw longevity, motility and motility parameters, and on plasma membrane functional integrity. Semen was diluted in two steps with an egg yolk TRIS extender containing a final concentration of either 5% glycerol or 5% ethylene glycol, and frozen in 0.5 ml straws, with 100 106 spermatozoa/ml, over nitrogen vapours. Semen motility was evaluated both under a light microscope and with a Computer Assisted Motility Analyser System, immediately after thawing and then hourly till 4 h of incubation. Sperm membrane functional integrity was assessed with the hypoosmotic swelling test (60 mOsm fructose solution) applied at thawing and then hourly, for 4 h, on incubated samples. Motility (light microscope) and total and progressive motility (analyser) were significantly higher in ethylene glycol frozen samples at thawing (P < 0.01); from hour 1 onwards the effect of the cryoprotectant became not significant. Semen frozen with ethylene glycol showed higher path velocity and higher straight line velocity till 3 h after thawing; however, ethylene glycol semen samples also showed higher curvilinear velocity and higher lateral head displacement, which may indicate a capacitation-like condition affecting sperm membranes and possibly reducing post-thaw longevity. Functional integrity of plasma membrane was similar in glycerol and ethylene glycol samples till 3 h after thawing, then ethylene glycol samples showed a higher decline. The strong though short-lived positive effect of ethylene glycol is worth being evaluated further.
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