EFECTO DE LA TEMPERATURA DE ALMACENAMIENTO DE EPIDÍDIMOS DE TORO SOBRE LA CALIDAD ESPERMÁTICA DE SEMEN CRIOPRESERVADO

Epididymis sperm conservation is a technique widely used in animals of high genetic value as well as in wild animals dead unexpectedly. One factor that most influence in motility and sperm membrane integrity (plasma and acrosomal) as well as the fertilizing ability of epididymal spermatozoa recovered is post-mortem temperature storage of epididymis. The objective of this study was determinate sperm quality pre-freezing and post-thawed of bull epididymal sperm (Bos taurus) from the Ecuadorian Amazon recovered from testicles stored to 5 or 20ºC for short-time. For this propose, ten pairs of testicles were collected from slaughterhouse. Left and right testicles of each bull were storage at 5ºC (T-5 group) or 20ºC (T-20 group), respectively during 6 hours (h). Sperm recovery was performed by retrograde flow of the epididymis tail and the liquid obtained was diluted in AndroMed® extender at concentration of 200 x 106 spermatozoa/ mililiters mL and packed in 0.25 mL straws. Both straws T-5 (n = 30) and T-20 (n = 30) groups were frozen in vapors of nitrogen liquid and thawed at 37ºC for 60 seconds (sec). The effect of storage temperature of epididymis post-mortem were assessment by ANOVA-one way. The results showed that in pre-freezing analysis, the percentage of motility (analyzed by optical microscopy), sperm vitality (V, plasma membrane integrity analyzed by eosin- nigrosine stain) and total morphological abnormalities (TA) of spermatozoa of T-5 group did no showed significant differences (P>0.05) compared with T-20 group. In post-thawed analysis, likewise the motilities variables (assessed by CASA system, SpermVision®, Minitube, Germany) as well as TA did no showed significant differences (P>0.05) between T-5 and T-20 groups. Sperm vitality (V) in samples thawed was higher (P<0.05) with T-5 group than T-20 group (63.0 ± 2.6% y 52.9 ± 3.0%, respectively). However, in plasma membrane functionality analysis assessed by hypoosmotic test (HOST) showed higher values (P<0.05) with T-20 group than T-5 group (40.4 ± 3.26% and 31.3 ± 1.99%). In conclusion, the results suggest that, despite the controversies found in the integrity and functionality plasma membrane post-thawed, the epididymis from Bull slaughtered under environment conditions of Ecuadorian Amazon may be storage at 5 or 20ºC during short-term. Additional studies should be made to evaluate the fertilizing ability of these epididymal sperm after artificial insemination (AI) under filed conditions.