Cytometric solutions in veterinary andrology: Developments, advantages, and limitations.

Cytometric methodologies are becoming increasingly important in veterinary andrology as means of assessing sperm function. However, as yet, flow cytometric techniques in veterinary andrology have not kept up in sophistication with those in other areas of biology and medicine. In this brief review, we consider the present state of cytometry in andrological procedures for evaluating the fertility of domestic animal sires. We outline the aspects of sperm physiology, paying particular attention to the changes that take place during the process known as capacitation, which prepares the sperm for interaction with the egg. We then examine briefly but critically the cytometric techniques that are currently in commercial use or are being established in research laboratories for testing sperm characteristics. Current limitations and potential developments in semen assessment are discussed. Recent research knowledge offers possibilities for applying more subtle flow cytometric approaches to distinguish different levels of fertilizing potential in semen samples. For example, linking field fertility data to multiparametric kinetic studies of sperm capacitational changes rather than "single parameter-single time point" estimations may reveal that slower rather than rapid changes indicate high fertility. Moreover, the development of multicolor flow cytometric procedures as a means of evaluating multiple functional parameters in individual cells would reduce the uncertainties always inherent in predicting fertility from in vitro sperm evaluation tests.