Fatty acids of rainbow trout ( Oncorhynchus mykiss) semen: Composition and effects on sperm functionality

The total fatty acid composition of rainbow trout ( Oncorhynchus mykiss) spermatozoa and seminal plasma was investigated in fresh and in stored semen using gas liquid chromatography. Triglycerides, phospholipids, and cholesterol were measured and the effect of fatty acids, triglycerides, and cholesterol on sperm functionality was evaluated. In seminal plasma and spermatozoa saturated fatty acids occurred in higher quantities than unsaturated fatty acids. In spermatozoa, the concentrations of monounsaturated fatty acids were higher than the concentrations of polyunsaturated fatty acids. In seminal plasma the concentrations were approximately equal. Myristic acid, palmitic acid, and stearic acid were main saturated fatty acids and oleic acid, vaccenic acid, and linolenic acid main unsaturated fatty acids of spermatozoa and seminal plasma. In spermatozoa linoleic acid, docosahexaenoic acid, eicosapentaenoic acid, arachidonic acid, and docosahexaenoic acid were found in high concentrations, too, in seminal plasma palmitoleic acid and eicosenoic acid. During semen storage the fatty acid composition changed in spermatozoa and in seminal plasma indicating that fatty acids were metabolized. Palmitic acid, the one of the main saturated fatty acids of spermatozoa and seminal plasma, and the unsaturated fatty acids, arachidonic acid and linoleic acid, which occur in spermatozoa and seminal plasma of rainbow trout, too, had a positive effect on sperm viability during immotile, unfrozen storage of spermatozoa as they increased the motility rate and average path velocity, which could be activated. Also the sperm fertility was improved by addition of fatty acids. A similar effect was found by arachidic acid, a saturated fatty acid, which was not detected in spermatozoa and seminal plasma. Therefore, semen short-term storage techniques can be improved by supplementation of storage solutions with fatty acids. Fatty acids had no effect on sperm motility duration. They had also no effect on sperm cryoresistance as the motility pattern and fertility of spermatozoa frozen–thawed with or without fatty acids were similar.