Making the most of sperm activation responses: experiments with boar spermatozoa and bicarbonate.

Attempting to extract useful and reliable information about semen quality and its fertility potential remains a difficult exercise, partly because the sperm heterogeneity within samples often renders simple statistical analyses rather meaningless. In fact, a mean and standard deviation may reflect neither the very fast swimming activities of the most active cells nor the slow and sluggish activities of others. Herein we propose that the information value within semen samples can be maximised if current knowledge about sperm activation mechanisms is exploited before undertaking the measurements. We explain, using boar semen as an example, that estimating and defining relative sperm subpopulation sizes, after activation by bicarbonate, provides a means of quantifying sperm quality. Although such estimates may indeed be related to in vivo fertility, the general approach also suggests potential new avenues that could be exploited for the elaboration of novel in vitro tests for the characterisation of toxic environmental chemicals and, indeed, to reduce the number of animals used in such testing programs.