Abstract: Disclosed herein are methods for determining the fertility of a sperm sample or a source of a sperm sample; the methods comprising labeling the sperm sample with a zinc probe, identifying presence and/or localization of zinc associated with spermatozoa in the sample and determining the fertility of the sample based on the zinc presence and/or localization in the spermatozoa as compared to a reference pattern associated with non-capacitated spermatozoa or a reference pattern associated with sperm capacitation. Also disclosed are methods of improving sperm fertility and/or decreasing premature capacitation while handling, storing, or transporting semen, the methods comprising adding exogenous zinc to a sperm sample or semen sample. Also disclosed are compositions for improving sperm fertility and/or reducing premature capacitation, the compositions comprising exogenous zinc ions.