Influence of equilibration time and freezing diluent on post-thaw motility and acrosomal integrity of epididymal sperm from the African buffalo (Syncerus caffer)

Abstract

The aim of this study was to test whether or not the equilibration time of two different cryodiluents influences the post thaw qualities of epididymal African buffalo (Syncerus caffer') sperm. Diluents and equilibration times were compared by assessing the post thaw spermatozoal motility, longevity and the acrosomal integrity. African buffaloes belong to Africa's "Big Five" and are, therefore, popular animals amongst game farmers, hunters and tourists. They are also asymptomatic carriers of foot-and-mouth-disease (FMD) and considered to be a wildlife reservoir for this plague. Other diseases, that are carried and can be transmitted from the African buffalo (Syncerus caffer') to livestock include tuberculosis, brucellosis and theileriosis or corridor disease (CD). Therefore, the transportation of African buffaloes is highly regulated. Disease-free buffalo populations are currently derived from a small genetic 8 pool and are smaller in their trophy size than the free-ranging animals from the diseased areas of the Kruger National Park (KNP) and the Hluhluwe/Umfolozi National Park. Hence there is a special interest in bringing new genetic material into the disease-free populations. Epididymal sperm from 11 mature African buffalo bulls was collected, diluted with two different semen extenders (TriiadylTM [Tris egg yolk extender] and AndroMed® [synthetic extender, i.e. fully defined medium]) and frozen. Pre-freezing equilibration times of 2 and 9 hours were tested. Total and progressive motilities, longevities and acrosomal integrity were measured and compared. Results show that there were no differences in post-thaw sperm quality when equilibration times between 2 and 9 hr were used. The use of the egg yolk containing extender (TriiadlyTM) resulted in higher percentage of post-thaw motilities than the use of the synthetic AndroMed®. Because a high percentage of progressive motile spermatozoa is one of the prerequisites for successful AI it must be concluded that TriladylTM is superior to AndroMed®. As I believe the advantages of higher motility to be bigger than the hygiene risks of a yolk containing extender I conclude that epididymal buffalo sperm should rather be frozen with TriiadylTM than with AndroMed®.