Recovery, cryopreservation and fertilization potential of bovine spermatozoa obtained from epididymides stored at 5 °C by different periods of time

Abstract

The objetive of the present study was to evaluate the effect of the interval between animal's death and sperm recovery on the freezability and fertilizing ability of spermatozoa from bull epididymides stored for different periods of time. Testis from 25 bulls were collected at the abattoir 2 h after the slaughter. In the laboratory spermatozoa from one epididymis were recovered and analysed for motility. The remaining epididymis was stored for 24 h (G24), 48 h (G48) and 72 h (G72) at 5 °C. At the end of each time period, spermatozoa were recuperated and cryopreserved in Tris-egg yolk and glycerol. Pre-freeze and post-thaw sperm samples were taken to assess total and progressive motility, concentration, membrane integrity and acrosome integrity. For evaluation of fertilizing ability, in each time period five straws of each bull were thawed, pooled and used for in vitro embryo production. The results showed that after 48 h of storage there was a decline in total motility, which did not change until 72 h. Progressive motility, plasma membrane and acrosome integrity were not affected by any of the storage periods. Conversely, all sperm parameters, except progressive motility, were reduced after cryopreservation. Embryo production was less ( P < 0.05) in the treatments than in the reference group. However, there was no differences ( P > 0.05) in blastoycst rate among experimental groups. Considering all the embryos produced by epididymal spermatozoa a greater proportion of female embryos was observed, which was similar to the reference embryos. The shift observed on sex ratio toward female for those two groups was also observed when they were compared with the expected 1:1 ratio ( P < 0.05). The results showed the possibility to produced in vitro embryos using cryopreseved spermatozoa from epididymides and stored for long period of time at 5 °C. These procedures became an important tool for animal preservation when the sperm cells cannot be cryopreserved immediately after the animal's death.