Effects of packaged volume on freezing and thawing rates and the fertility of cryopreserved sperm of yamú (Brycon amazonicus)

Abstract

The aim of this study was to evaluate the freezing-thawing conditions of yamú (Brycon amazonicus) sperm packaged in straws of different volume and their effect on the spermatic motility and fertility post-thawing. The induction to gonadal final maturation was made with carp pituitary extract. The sperm obtained was evaluated and diluted (1:4) in a solution with 5.5% glucose, 12% egg yolk and 10% dimethyl sulfoxide, packaged in 0.5, 1.8, 2.5 or 4.0 ml straws and frozen in nitrogen vapors. The thawing was carried out in a 35°C, 60°Cor 80°C water bath during different times. All straws showed a similar overall freezing rate (7.5 to 12.9°C min^-1). On the other hand, the overall thawing rate was faster at a higher water bath temperature. The 4.0 ml straws thawed at 35°C showed the highest motility and activation time post-thaw (47.0 ± 1.6% and 60.2 ± 2.4 sec). The fertility obtained with cryopreserved sperm in all straw sizes was significantly lower (P < 0.05) than with fresh sperm (65 ± 4%). The highest fertility was observed with 0.5 ml straw thawed at 35°C (52 ± 3%), followed by 2.5, 4.0 and 1.8 ml straws (51 ± 3, 48 ± 3 and 47 ± 3%, respectively). It was concluded that 4.0 ml straws thawed at 35°C showed the best post-thaw sperm quality and more homogenous freezing-thawing rates in comparison to the other packaging systems. On the other hand, no effects on fertility were observed in all straw sizes thawed at 35 °C.