Studies of the factors causing abnormal acrosomes and crooked-necks in fowl spermatozoa during freezing and thawing

In order to investigate the factors causing crooked-necked spermatozoa (CNS) or those with abnormal acrosomes during freezing and thawing, fowl spermatozoa in NaCl or glucose solutions containing 92 ml glycerol/l were examined using a scanning electron microscope before and after freezing and thawing. The incidence of CNS in NaCl solution significantly increased after freezing and thawing, but not in glucose solution. The acrosomal damage caused by freezing and thawing was considerable in both solutions, and the incidence of damage in glucose solution was significantly higher than that in NaCl solution. In neither solution was there a significant difference between the incidence of acrosomal damage in CNS and in non-CNS. The ratios of incidences of abnormal acrosome after, versus before, freezing were higher in non-CNS than in CNS. It appears from these results that the factors during freezing and thawing which cause CNS may differ from those causing acrosomal damage.