Semen cryopreservation of rainbow trout XX-males. / CriopreservaÃÃo do sÃmen de machos-XX de truta arco-Ãris (Oncorhynchus mykiss)

AUTOR(ES)
DATA DE PUBLICAÇÃO

2007

RESUMO

This study was carried out during July and August of 2005 and 2006. The aim of this study was to improve the cryopreservation techniques for semen cryopreservation of sex-reversed rainbow trout males (XX-males). The first session of experiments, only semen collected under abdominal massage was used. In experiment 1, four semen extenders (glucose 5,4%, NaCl 0,9%, NaCl 1,2%-tris and BTSÂ) and the addition of egg yolk at 0 and 5% to the freezing media were tested. Then the effects of DMSO, ethylene glycol, methylglycol and methanol as cryoprotectants, semen dilution ratios of 1:3 and 1:7 (experiment 2), straw volumes of 0.25; 0.5 and 4.0 ml (experiment 3) and thawing at a water bath temperatures of 70ÂC/3s, 60ÂC/8s and 50ÂC/8s (experiment 4) on post-thaw sperm motility were evaluated. In experiment 5, post-thaw semen was used at different sperm:egg ratios (15x106 to 60x106) and eyed-egg rate was calculated after 196ÂC days. In all theses five experiments, semen was cryopreserved in nitrogen (N2) vapor at -170ÂC for 12-16 h, then transferred to a liquid N2 vessel. During the second session of experiments, only intratesticular semen obtained after male sacrifice was used. In experiment 1, semen was cryopreserved in one extender (glucose 5,4%, NaCl 0,9% or NaCl 1,2%-tris), egg yolk and DMSO according to the method described previously, and thawed at 70ÂC/3s or 35ÂC/16s. Then the pre-freezing incubation of semen diluted (1:0, 1:6 or 1:8, experiment 2; 1:5, 1:7 or 1:9, experiment 3) in seminal plasma and frozen in glucose or NaCl as extender (experiment 3), egg yolk and DMSO was tested. When semen was collected under abdominal massage, the highest post-thaw sperm motilities were observed in those samples diluted 1:3 in glucose, egg yolk and DMSO as freezing medium, cryopreserved in 0.5-ml straws and thawed at 70ÂC/3s. The highest eyed-egg rates were observed when sperm:egg ratio was above 30x106. When intratesticular semen was immediately cryopreserved without the incubation period, very low post-thaw sperm motility were observed. However, when intratesticular semen was diluted 1:6 in seminal plasma, incubated for 1:30h and cryopreserved in glucose, egg and DMSO, post-thaw sperm motility increased from 18% (without incubation) to 60% (after incubation). Based in these results we can conclude that semen of rainbow trout XX-males can be successfully cryopreserved in a freezing medium containing glucose, egg and DMSO, in 0.5-ml straws and thawed at 70ÂC/3s. If intratesticular semen is used, than the pre-freezing incubation period of 1:30h in seminal plasma is mandatory.

ASSUNTO(S)

trout criopreservaÃÃo semen zootecnia truta sÃmen cryopreservation

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