Source of dietary lipid affects sperm plasma membrane integrity and fertility in rainbow trout Oncorhynchus mykiss (Walbaum) after cryopreservation

The effects of dietary lipid from 4 experimental diets on the fatty acid composition and cholesterol content of spermatozoa and their plasma membranes and their consequences for sperm viability after cryopreservation were evaluated in rainbow trout. The 4 sources of lipid were herring oil (adequate n-3 fatty acid), menhaden oil (high n-3 fatty acid), safflower oil (high n-6 fatty acid ) or tallow (high saturated fatty acid), and they comprised 12% of the total diet. Spermatozoa from fish fed the tallow diet had significantly (P<0.05) higher cholesterol levels than spermatozoa from the fish fed the other diets. The spermatozoa plasma membranes from fish fed the tallow diet had significantly (P<0.05) higher cholesterol and monounsaturated fatty acid levels than those from fish fed the menhaden or safflower oil diets, but were not different from membranes of fish fed the herring oil diet. Cryopreserved spermatozoa from fish fed the tallow or herring oil diets exhibited less membrane damage (P<0.05) and produced a higher percentage (P<0.05) of eyed embryos compared with spermatozoa from the menhaden or safflower oil-fed fish. Therefore, it would appear that high levels of cholesterol and monounsaturated fatty acids provided the spermatozoa with increased resistance to cryopreservation damage..