Effects of astaxanthin supplementation on the freezability, lipid peroxidation, antioxidant enzyme activities and post-thawing fertility of ram semen

The aim of present study was to determine the effect of astaxanthin supplementation of the semen extender on post-thaw semen quality and fertility. Semen samples were collected from four fertile rams by using an artificial vagina, pooled and diluted with a Tris-citric acid-fructose-yolk extender, supplemented with AST at 0.5, 1, 2, or 4 mu M concentraitons. For the control group, semen was processed in the basic extender without AST. Extended semen was aspirated into straws which were cooled to 5 degrees C and frozen on liquid nitrogen vapor. After 24 h, the straws were thawed in a water bath for 30 s. The results showed that supplementation of the extender with 2 and 4 mu M AST increased the sperm viability and plasma membrane integrity in frozen-thawed semen compared to other groups (P < 0.05), whilst there was no significant difference between extenders containing 0.5 and 1 mu M AST. Freezing the sperm in the extenders containing 2 and 4 mu M AST led to lower percentages of acrosome abnormalities (27.20% +/- 0.54 and 28.15% +/- 0.54, respectively) and malondialdehyde formation (1.70 +/- 0.1 and 1.81 +/- 0.2 nmol/ml, respectively) in comparison to other treatments (P < 0.05). There was no effect of AST on SOD and GSH-PX activities (P > 0.05). Higher fertility rates were obtained when semen extender contained 2 mu M (48.33%) and 4 mu M (45.76%) AST compared with control group (21.15%). The results showed that, inclusion of AST in frozen ram semen extenders could improve seminal quality and fertility rate.