In vitro evaluation of ram sperm frozen with glycerol, ethylene glycol or acetamide.

The aim was to assess the in vitro effect of glycerol, ethylene glycol or acetamide on frozen-thawed ram spermatozoa. Aliquots of each sixteen ejaculates from four rams of the Morada Nova breed were diluted in Tris-egg yolk with glycerol (5%), ethylene glycol (3% or 5%) or acetamide (3% or 5%) and frozen at -196°C. After thawing, progressive sperm motility was greater (P<0.05) in cryopreservation with glycerol 5% and ethylene glycol (3% or 5%) than with acetamide (3% or 5%). Acrosome integrity was greater (P<0.05) with ethylene glycol 5% than acetamide (3% or 5%). The percentage of sperm without oxidative stress was greater (P<0.05) with ethylene glycol (3% or 5%) than with acetamide (3% or 5%). Plasma membrane integrity was greater with glycerol 5% (P<0.05) than with the other cryoprotectants. Thus, it is concluded that glycerol 5% and ethylene glycol 3% or 5% protect ram sperm against the harmful effects of freezing and that glycerol 5% offers greater protection to sperm plasma membrane.