Rooster sperm pellet cryopreservation protocols: effect of step variations on the qualitative parameters of post-thawed sperm

The cryopreservation of sperm into pellets is not the preferred way to package avian semen but is quick and easy to do and does not require sophisticated technology. The aim of this study was to evaluate rooster sperm viability and mobility and the incidence of normal cells and sperm injuries in post-thawed pelleted sperm. The outcomes of different pelleting protocols were evaluated, which varied according to the parameter combinations used in each of the critical steps of the freezing process and in the thawing conditions which differed in methodology and temperature. The protocols employing 6% DMA showed the highest values of thawed sperm mobility. The most favourable thawing method in terms of sperm mobility was using the hot-plate at 60 degrees C, followed by the water-bath at 50 degrees C. The protocols resulting in the best sperm quality parameters employed a 1:2 dilution rate, a 30-min equilibration time at 4 degrees C, 6% DMA, and thawed 80 mu L pellets using the water-bath at 50 degrees C or the hot-plate at 60 degrees C. According to the parameters evaluated, rooster sperm was highly susceptible to damage caused by the freezing-thawing methodology, although the survival rate of normal sperm cells still reached 39%, with 32% recovered mobility with respect to fresh sperm samples.