Physiology and Endocrinology: Sperm Fertility, Embryos and Development

Mammalian spermatozoa experience osmotic stress when the glycerol is added to the cells before freezing and removal from the cells after thawing. To minimize osmotic damage, alternative cryoprotectants, having lower molecular weights and greater membrane permeability than glycerol, were evaluated to determine their effectiveness for cryopreserving bull spermatozoa. The primary goal of this study was to compare glycerol as the most common cryoprotectant of bull spermatozoa to ethylene glycol and methyl as alternative cryoprotectants. Bull semen was diluted with tris-egg yolk extender containing 3% glycerol, 3, 2 and 1% ethylene glycol and 3, 2 and 1% methyl. Bull semen was frozen in pellets form using the cold surface of cattle fat. Computer assisted sperm analysis (CASA) assay was used to study the post-motility properties of bull spermatozoa. Bull spermatozoa exhibited higher percentages (P < 0.01) of all motile spermatozoa properties when frozen in extender containing 3% glycerol compared with 3, 2 and 1% ethylene glycol or 3, 2 and 1% methyl cryoprotectants. It is concluded that glycerol concentrations of 3% in the extender is the most suitable cryoprotectant for cryopreservation of bull spermatozoa.