Evaluation of Different Concentrations of Egg Yolk in Canine Frozen Semen Extender

This study tested different concentrations of egg yolk in canine freezing extender void of glycerol, a commonly used cryoprotectant, by examining the motility and morphology throughout the freezing process: initial (baseline after extender added), post-cool (after three hours at 5"C) and post-thaw (after freezing.)  Initial values of pH, osmolarity, motility and morphology were obtained for comparison of the samples.  Spermatozoa from six normal dogs as determined by progressive linear motility > 70% and normal morphology > 60% was used. Semen was collected and pooled for five freezing trials.  The concentrations of egg yolk used in the extender were: 0%, 10%, 20%, 30% and 40%. Assessment of each sample was blinded to the treatments until all results were obtained and statistics had been analyzed. Based on this study a 20% egg yolk concentration is slightly superior to a 30% egg yolk concentration when assessing post-thaw motility, morphology and longevity and significantly superior to a 0%, 10% or 40% egg yolk concentration. The study also showed motility and normal post-cool and post-thaw sperm morphology did not always correlate.  Utilization of 0% and 10% concentrations of egg yolk has negative effects on semen quality as measured by the motility and/or morphology.  Results confirm freezing does not affect secondary sperm abnormalities, abnormalities of the tail and distal section of the middle piece, during cooling or freezing.  Primary abnormalities, abnormalities of the head and midpiece, increased in the 0% extender during cooling and all extenders during freezing. The pH of the extenders before the addition of sperm was significantly different. Once sperm was added to the extenders, there was no longer a significant difference in pH.  There was a positive correlation for both motility and normal morphology percentages post-cool and post-thaw for the extenders with similar osmolarity to the semen.