The effect of different egg yolk, sugars and buffering systems concentrations in the freezability of differents equine semen extenders was studied. Extenders were: D1=10% of egg yolk added of more 50% over the lactose and glicose-EDTA levels found in D5; D2=10% of egg yolk and reduction of 50% over the lactose and glucose-EDTA levels in D5; D3=20% of egg yolk added of more 50% over the lactose and glucose-EDTA levels in D5; D4=20% of egg yolk and reduction of 50% over the lactose and glucose-EDTA levels in D5; D5=20% of egg yolk and lactose and glucose-EDTA according to Martin et al. (1979). Five ejaculates of six stallions were used to test extenders using alternatively two differents cryoprotectants agents: 3.5% ethylene glycol and 5% acetamide. After the final dilution, the semen was submitted to differents freezing rates. Straws were thawed at 75º C during 7 seconds, followed by immersion at 37ºC during 5 seconds. After thawing motility, vigour, structural and functional integrity of the membrane of the spermatozoa were evaluated. The reduction in the egg yolk concentration from 20% to 10%, in extenders with the same concentration of sugars and buffering systems, did not modify the crioprotectant capacity of the extender with ethylene glycol or acetamide. The increase in the concentration of sugars and buffering systems in the lactose-EDTA-egg yolk extender did not add crioprotectant effect to ethylene glycol and acetamide. Extenders with high osmolarity had tended to better preserve the frozen equine semen with ethylene glycol or acetamide. Better results of spermatic viability, after thawing, were obtained when semen was diluted in D1, D3 and D5 extender (P<0.05).
equine; semen; cryopreservation; extender
