Effect of post-mortem time on post-thaw characteristics of Spanish ibex (Capra pyrenaica) spermatozoa

Viable epididymal sperm can be obtained in the Spanish ibex during 24 h after death, but it has been observed a significant effect of the post-mortem time on fertility success, so only goats inseminated with semen recovery during the first 8 h became pregnant. The aim of this study was to determine the effect of post-mortem time on epididymal semen samples from of Spanish ibex. For this purpose, sperm samples from 36 males were collected at different post-mortem times, from 2 to 24 h, and cryopreserved. Thawed samples were incubated for 2 h at 37 °C without dilution or after dilution in a modified Tyrode medium, in order to study the sperm resistance to dilution. Moreover, flow cytometry was used to assess the sperm viability (PI), phospolipid disorder of the plasma membrane (M540), mitochondrial membrane potential (Mitotracker Deep Red), indirect apoptosis markers (YOPRO-1) and sperm chromatin stability (SCSA®). Sperm motility was evaluated by computer-assisted sperm analysis (CASA). Our results have shown that post-mortem time caused a reduction in mitochondrial membrane potential. In this regard, the loss of energy could be responsible for the loss of maintenance of the membrane with a consequent increase in permeability leading to a decrease in sperm viability and motility, losing linearity and speed. Moreover, the loss of maintenance of the membrane influence the extent to which sperm will survive the cryopreservation process, as it shows the results obtained from the dilution–incubation resistance test. Finally, one important finding of this study is the demonstration of no effect of post-mortem time on post-thaw DNA integrity, giving us the possibility of using sperm samples from valuable males, even if it was not possible to process during the first 8 h.