Motility, morphology and triple stain analysis of fresh, cooled and frozen-thawed stallion spermatozoa

The aim of the present study was to determine whether there are characteristics of fresh, cooled and frozen-thawed semen samples that can be used to predict the suitability of stallion semen for preservation by cooling or freezing. Each of three ejaculates obtained from 12 stallions was divided into aliquots to be analysed for sperm motility, morphology and membrane integrity as fresh, cooled and frozen-thawed samples. The percentage of morphologically normal spermatozoa was similar in fresh and cooled samples and both were greater than in the frozen samples. There were no strong linear relationships in the percentages of progressive motility, live spermatozoa and morphologically normal spermatozoa in fresh, cooled and frozen-thawed semen samples. Although the percentages of motile spermatozoa in fresh, cooled and frozen samples were linearly related, when sperm motility was ranked as excellent, good, fair and poor, the only correlation observed was between progressive sperm motility in fresh samples and total sperm motility in frozen samples. The results of the present study demonstrate that the high percentage of progressive motility in fresh semen samples is not indicative of similar patterns in cooled or frozen-thawed samples. Commonly used methods for assessing sperm function do not appear to be useful for predicting the ability of stallion semen to withstand preservation by either cooling or freezing.