Apoptotic markers can be used to forecast the freezeability of stallion spermatozoa

In an attempt to identify valuable markers for potential freezeability of the equine spermatozoa, three ejaculates were collected from five Andalusian stallions and frozen using a standard protocol. Before freezing, three apoptotic cell markers were studied by flow cytometry (early changes in sperm membranes, mitochondrial membrane potential and caspase activity). Post-thaw, spermatozoa were again evaluated for these parameters. Sperm kinematics using CASA were also studied before and after freezing and thawing. Receiving operating system curves were used to evaluate the relative value of the apoptotic markers herein studied, as forecast for potential freezeability. From all parameters studied, the outcome of JC-1 (as proportion of spermatozoa showing simultaneously orange and green fluorescence) had the highest diagnostic power. For potentially bad freezers (less than 25% of intact spermatozoa post-thaw), the significant area under the ROC-curve was 0.985, with a 100% sensitivity and 99.8% specificity for a cut off value of 55.7.