The effects of extender type, freezing and thawing rates on fertility of the cryopreserved semen of the Caspian brown trout (Salmo trutta caspius )

Cryopreservation of semen from the Caspian brown trout (Salmo trutta caspius) and effects of extender type, freezing and thawing rates on fertilization ability were studied. After assessment of semen quality, one part of semen was diluted with three parts of different extender and decanted into ۰.۵ml straws. Freezing was carried out at two freezing levels, ۱.۵cm and ۲cm above surface of liquid nitrogen. The semen was thawed at ۵°C for ۹۰s, ۱۵°C for ۴۵s or ۲۵°C for ۳۰s in water baths and used for fertilization. Using the extender: ۰.۳ M glucose+۱۰% methanol+۱۰% egg yolk, and ۰.۶ M sucrose ۱۰% DMSO + ۱۰% egg yolk, yielded the highest post-thaw fertilization rates, with ۶۷.۰۵%±۸.۷۶ and ۵۹.۷۸%±۵.۰۸ eyeing rates, respectively. No significant differences were found in the fertilization rates with two freezing levels (P>۰.۰۵), however eyeing and hatching rates were higher for ۲cm above the surface of the liquid nitrogen than for ۱.۵cm. Thawing of cryopreserved semen was best using the ۲۵°C water bath for ۳۰s and significant differences were seen in the eyeing rates between ۲۵°C and ۵°C or ۱۵°C (P<۰.۰۵). Significant interactions (P<۰.۰۵) were found between effects of extender type and thawing rates and extender type and freezing rates.

کلیدواژه ها:

Cryopreservation ، Extender ، Freezing ، Thawing ، Fertility ، Salmo trutta caspius