USE OF WATER TEST TO ASSESS THE SPERM MEMBRANE FUNCTIONAL INTEGRITY IN CRYOPRESERVED BULL SEMEN Uso de la prueba de agua para medir la integridad funcional de la membrana espermática en semen criopreservado de toros

The hypoosmotic swelling test (HOST) has been used to asses the sperm membrane functional integrity in bulls. However, for human, goat and dog semen, the water test (WT) has been proposed as a replacement to HOST, because WT uses disti­ lIed water and only five minutes of incubation. The aim of the present study was to compare the HOST and the WT to as­ sess the sperm membrane functional integrity of cryopreserved bull semen. The percentage of sperm with swelling tail was higher in WT (54.85 ± 13.63%, P<0.0001) than HOST (42.90 ± 12.89%), but both were correlated positively (r = 0.77, P<0.0001). In comparison with viability of thawed semen (52.52 ± 9.79%), only WT diminished significantly this parame­ ter to 45.95 ± 8.69%, P<0.0001. Acrosome integrity of thawed semen (82.35 ± 8.21 %) decreased significantly after HOST (57.87 ± 12.67%) and WT (39.00 ± 16.88%). Acrosome inte­ grity in thawed semen was correlated positively with results af­ ter HOST (r = 0.52; P = 0.0126) and WT (r = 0.52; P = 0.0115). In conclusion, the WT can assess the sperm membrane func­ tional integrity of cryopreserved bull semen and is able to re­ place the HOST.