Fatty acid composition of ovarian fat and ovary of farmed Russian sturgeon (Acipenser gueldenstaedtii)

The deposition and proliferation of adipose tissue in the ovaries of mature female sturgeons is one of the most recent issues in caviar production. Lean ovaries tend to produce a greater yield of superior quality caviar than those with fatty ovaries. In addition, the excess of adipose tissue in the ovary cause complications during the processing and the separation of eggs from ovarian stroma. To reduce this phenomenon farmers usually introduce a dietary shift at the end of the culture period, reducing the feed administration or switching to a lower fat feed during the last weeks before the caviar extraction; other farmers introduce a starvation period. The aim of present preliminary research was to evaluate the fatty acid composition of samples of ovarian adipose tissue and compare them with the fatty acid composition of eggs of Russian sturgeon. Five samples of ovarian residues obtained after eggs separation and five samples of eggs were analysed. Fatty acid composition of the two tissues presented some differences; monounsaturated fatty acid, in particular oleic acid (18:1 n-9) were found in higher concentration in ovarian tissue than in eggs, while docosahexaenoic acid showed an opposite trend. Results suggested than some fatty acid were stored mainly in fat tissue and were less included in oocyte, suggesting that the problem of fat ovaries could be linked more to the fatty acid composition of the diet than to its lipid content. Further studies are needed to investigate the correlation between the fatty acid composition of the diet and the ovarian fat deposition.