Incidence of (n-3) essential fatty acid deficiency on trout reproductive processes.

A feeding experiment was conducted on rainbow trout broodstock for one year to investigate the influence of the quality of dietary lipids on egg and fry fatty acid composition, embryonic development and hatching efficiency. The broodstock were fed either a commercial control diet or a (n-3) fatty acid-deficient diet; their liver, eggs and fry were analysed to determine the fatty acid composition of their neutral and polar lipids. The fatty acid pattern in liver, eggs and fry was markedly different due to the qualitative difference of the dietary lipids. The most striking difference was the low amount of 22:6 (n-3) and the high levels of 20:4 (n-6) and 22:5 (n-6) in phospholipids of fish receiving the (n-3)-deficient diet containing a high level of 18:2 (n-6). While fertilization efficiency was equivalent in the first two days of development, whatever the diet, two peaks of mortality were observed, one at day 8 and the other at day 22 after fertilization, during the time the eggs produced by the deficient fish were incubated. A shorter period of vitellus resorption (50 vs 65 day) was observed in (n-3)-deficient alevins as compared to controls. Morphological study of the development of the (n-3)-deficient embryos showed some cleavage disorders at the 16 to 32-cell stage, a blocking effect before gastrulation, and later various alterations in organogenesis. It was concluded that (n-3) fatty acids, and especially 22:6 (n-3), play a crucial and specific role in trout embryo development. These fatty acids could be involved in cellular recognition processes through their oxygenated derivatives. The need for long-term nutritional deficiency to induce the reported biochemical and physiological alterations is discussed.