Effect of supplementations of docosahexaenoic acid (DHA) into a Tris-glucose based extender on the post-thaw sperm quality, fertility and hatching rates in brown trout (Salmo trutta macrostigma) following cryopreservation

The supplementation of extenders with PUFAs has not been investigated in fish by now. Thus, the present study examined whether different levels of docosahexaenoic (DHA), which is the predominat PUFAs in sperm plasma membrane, in Tris-glucose based extender could increase the quality and fertilizing ability of brown trout (Salmo trutta macrostigma) sperm following cryopreservation were evaluated. Sperm samples diluted (1:10) with the base extender were supplemented with 1, 2.5, 5, 7.5 and 10 ng mL-1 concentrations of DHA. In the control group, sperm was diluted in the base extender, without DHA. Following dilution, the sperm was aspirated into 0.25 mL straws, frozen 3 cm above of the liquid nitrogen (LN2) surface, and plunged directly into the LN2. Based on the results, increasing of DHA supplementations in the Tris-glucose based extender improved post-thaw progressive motility, progressive duration of motility, viability, and fertility compared to the control group (p <0.05). Additionally, the results indicated that supplementation of 7.5 ng mL-1 of DHA significantly exhibited the best cryoprotective effect in terms of progressive motility (62.4±1.73%), progressive duration of motility (46.8±1.32s), viability (56.2±1.20%), fertility (52.6±1.48%), and hatching (28.6±1.45%). The results showed that supplementation of DHA to the Tris-glucose based extender can be beneficial for the cryopreservation of brown trout sperm.