The efficacy of different combinations of cryoprotectants for equine semen was evaluated. Three ejaculates of eight stallions were used to test the lactose-EDTA-egg yolk extender with the following association of cryoprotectants: T1 - glycerol 5% (control group); T2 - methyl cellulose 0.5%, raffinose 0.15g, and acetamide 2.5%; T3 - methyl cellulose 0.5%, raffinose 0.15g, and acetamide 3.5%; T4 - methyl cellulose 0.5%, raffinose 0.15g, and acetamide 5%; T5 - glycerol 5% and 2.4g of dried skim milk; T6 - glycerol 1%, ethylene glycol 4%, and 2.4g of dried skim milk; T7 - ethylene glycol 5% and 2.4g of dried skim milk. After collection, Kenney extender was added to the semen 1:1, and centrifuged at 400 x g for 12 minutes. Sperm pellets were diluted to reach 100x10(6) cells/ml. Spermatozoa were frozen in 0.5ml straws 3cm above the nitrogen level, during 10 minutes. Thawing of samples was done at 75°C for seven seconds followed by immersion of the straw in a water bath at 37°C for 30 seconds. Post-thaw total and progressive motilities and sperm vigor were evaluated. Sperm membrane integrities of the tail and caput, respectively, were evaluated by the hypoosmotic swelling test and fluorescent dyes. T1 showed the highest post-thaw total and progressive motilities (38.4% and 33.8%, respectively). No significant difference was found among treatments for vigor and hypoosmotic swelling test. T5, T6, and T7 showed higher post-thaw values for sperm membrane integrity. It may be concluded that the association of cryoprotectants used in this experiment did not result in better cryoprotectant effect than 5% glycerol for equine semen cryopreservation.
equine; semen; cryoprotectant; cryopreservation
