RESUMO
The work described here aimed to verify the efficiency of different extenders for cryopreservation of equine semen using sperm motility and acrosin activity as spermatic parameters. The semen was fractioned into two equal parts and resuspended in an 11% lactose solution in a 1:1 proportion, where it remained for 20 minutes at room temperature. The semen was centrifuged at 600 g for 10 minutes, and after the second centrifugation, each pellet received the freezing extender (Merck or Zorlesco) and was loaded into 4 mL straws. Each straw was placed in liquid nitrogen vapor steam for 15 minutes and further immersion in liquid nitrogen at -196°C for long-term storage. After thawing, semen samples were initially evaluated for sperm motility, both total and progressive, and acrosin activity. Moreover, semen was incubated at 37°C and further assessed at 60 and 120 minutes in a thermoresistance test (TRT) for sperm motility and acrosin activity. Immediately after thawing, both progressive and total motility, and acrosin activity were lower (p < 0.05) in thawed semen than in fresh semen. During the TRT, total sperm motility and acrosin activity after 60 minutes were lower (p < 0.05) than those obtained after thawing. Similarly, total sperm motility and acrosin activity were lower (p < 0.05) after 120 minutes than at 60 minutes of the TRT. The analysis of motility and acrosin activity allowed the conclusion that both extenders have a similar capacity to preserve the integrity of sperm cells subject to freezing and thawing.