Effect of prefreeze treatment on the fertilizing capacity of frozen chicken semen

ABSTRACT The object of this study was to evaluate the effects of extender osmotic pressure (251, 332, and 434 mOsm), extender pH (6.5, 7.0, and 7.5), extender fructose concentration (0, 2.5, 5, and 10 g/liter), and diluting prior to freezing to a constant sperm number (.5,.8, 1, or 2 X 10 ' sperm/ml) on the fertilizing capacity of processed-unfrozen and frozen-thawed chicken sper-matozoa. Fertilizing capacity of processed-unfrozen spermatozoa was not affected by changes in extender osmotic pressure, pH, or fructose concentration; it was significantly depressed, Days 2 to 4 postinsemination, by diluting to.5 X 109 sperm cells/ml, whereas all other dilution rates had little effect. Fertilizing capacity of frozen-thawed spermatozoa was highest (42 to 51%, Days 2 to 4 postinsemination) when diluted in an extender containing 5g/liter of fructose with an osmotic pressure of 332 mOsm and a pH of either 7.0 or 7.5. Fertility (51%, 2 to 4 days after insemination) obtained with frozen-thawed semen diluted to 1 X 109 sperm cells/ml was significantly higher than all other dilutions. The fertilizing capacity of frozen-thawed spermatozoa was generally lower than that of processed-unfrozen spermatozoa regardless of the experimental treatment