Quality of eggs and spermatozoa of rainbow trout fed an n-3 essential fatty acid-deficient diet and its effects on the lipid and fatty acid components of eggs, semen and livers

R. Vassallo-Agius, T. Watanabe, G. Yoshizaki, S. Satoh, Y. Takeuchi-2001

Fisheries Science, 67(5): 818-827

Abstract:

The effect of an n-3 essential fatty acid (EFA) -deficient diet on spawning and on the lipid and fatty acid contents of eggs, semen and livers of rainbow trout Oncorhynchus mykiss was investigated. Fish were split into two groups and fed either of two diets for a period of 4 months prior to the start of the spawning season. The control group was fed a commercial diet, containing n-3 EFA, whereas the experimental group was fed an n-3 EFA-deficient diet. Fish were 3 years old at the time of spawning. Eggs and semen were stripped off five females and five males from each diet group and cross-fertilized. Two of the five males fed the deficient diet showed a lower sperm motility, resulting in slightly lower mean hatching rates when crossed with eggs of either group. Higher lipid contents in the EFA-deficient diet were reflected in the egg and semen lipid contents, whereas the lipid contents of male livers of both diet groups were higher than those of female livers. In livers and eggs, the main polar lipid was phosphatidylcholine accompanied by phosphatidylethanolamine in sperm polar lipids. The non-polar lipids of eggs were mainly triacylglycerols but in livers and semen, free fatty acids and free sterols were more abundant. Essential fatty acids, namely n-3 highly unsaturated fatty acids and linolenic acid, were generally lower in eggs, semen and livers sampled from the EFA-deficient diet group. These results indicate that the fertilization, eyed and hatching rates obtained from crossings with males fed the EFA-deficient diet were slightly lower because of the dietary effect on sperm motility. Moreover, lipids of eggs, semen and livers of male and female rainbow trout were influenced greatly by their dietary availability.

(Department of Aquatic Bio-Sciences, Tokyo University of Fisheries, Minato, Tokyo 108-8477, Japan, Tel: 81-3-5463-0555. Email of T. Watanabe: watana@tokyo-u-fish.ac.jp)

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