Colloidal centrifugation of stallion semen increases ex vivo sperm DNA longevity

interaction between stallion and extender with respect to freezability. To evaluate the differences between “poor” and “good” freezers, the stallions grouped into the same cluster with both the extenders (5 and 3, respectively) were considered.When datawere compared prior to freezing, no differences were reported for TM, DFI, MI, HF and mitochondrial membrane potential, while VAP showed higher values in “good” freezer (P < 0.01). After centrifugation, “poor” freezers presented a worsening in TM (P < 0.01). After thawing, “good” freezers had lower DFI (P< 0.01) and higher TM (P< 0.01) and VAP (P< 0.01) compared to “poor” freezers. Furthermore, lower MI (P < 0.001) and greater HF (P < 0.01) and percentage of sperm with inactive mitochondria (P< 0.05)were reported for “poor” freezers. These results show that the damage induced by cryopreservation in “poor” freezers affects several sperm compartments: DNA, cell membranes and mitochondria. The discordant clustering of some stallions associated with different extenders, confirms previous observations suggesting the use of freezing protocols specific for each individual stallion to improve results semen cryopreservation.