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 four experimental diets on the fatty acid (FA) composition and cholesterol (CHOL) content of spermatozoa and spermat ozoal plasma membranes and their consequences for sperm viability after cry opreservation were evaluated in rainbow trout Oncorhynchus mykiss (Walbaum) . The four sources of lipid were herring oil (adequate n-3 FA), menhaden oi l (high n-3 FA), safflower oil (high n-6 FA) or tallow (high saturated FA), and they comprised 12% of the total diet. Spermatozoa from fish fed the ta llow diet had significantly (P < 0.05) higher CHOL levels than spermatozoa from the fish fed the other diets. The spermatozoal plasma membranes from f ish fed the tallow diet had significantly (P < 0.05) higher CHOL and monoun saturated fatty acid levels than those from fish fed the menhaden or safflo wer oil diets, but were not different from membranes of fish fed the herrin g oil diet. Cryopreserved spermatozoa from fish fed the tallow or herring o il diets exhibited less membrane damage (P < 0.05) and produced a higher pe rcentage (P < 0.05) of eyed embryos compared with spermatozoa from the menh aden or safflower oil-fed fish. Therefore, it would appear that high levels of CHOL and monounsaturated fatty acids provided the spermatozoa with incr eased resistance to cryopreservation damage.