The effects of dietary linolenic acid to linoleic acid ratio on growth performance, tissues fatty acid profile and sex steroid hormone synthesis of yellow catfish Pelteobagrus fulvidraco

The effects of different linolenic acid (LNA)/linoleic acid (LA) on tissues fatty acid composition and steroid hormone secretion of the female yellow catfish Pelteobagrus fulvidraco were evaluated after an 8-week feeding trial. Four isonitrogenous and isolipidic formulated diets were designed to contain different LNA/LA ratios of D0.27, D0.82, D1.71 and D2.63, respectively. The result showed that there were no significant effects on the weight gain (WG), gonadosomatic index (GSI), condition factor (CF) of yellow catfish among different diet treatments (P > 0.05). The relative fecundity was greatest in the D2.63 group (P < 0.05). The muscle and hepatic fatty acids profiles reflected corresponding dietary fatty acid profiles treatments, but not ovary. Eicosapentaenoic acid (EPA), arachidonic acid (ARA) and n-3 polyunsaturated fatty acid (PUFA) concentrations were significantly increased with increasing dietary LNA/LA ratios, in both muscle and liver (P < 0.05). ARA and highly unsaturated fatty acid (HUFA) concentrations in the egg were higher than that in liver and muscle, ARA was preferentially accumulated in yellow catfish gonad, which was not influenced by the dietary LNA/LA ratios. The levels of serum testosterone (T) decreased with increasing diet ratios of LNA to LA (P < 0.05), and the mRNA levels of steroidogenesis-related genes (CYP17a1, CYP19a and er beta) were significantly down-regulated with increasing dietary LNA/LA ratios in ovary of female (P < 0.05). In parallel with the changes of plasma follicle-stimulating hormone (FSH) and luteinizing hormone (LH), the mRNA levels of 20 beta-hydroxysteroid dehydrogenase (20 beta-HSD) upregulated with increasing LNA/LA ratios (P < 0.05). In conclusion, the present results suggest that dietary LNA/LA ratios regulated steroid hormone synthesis during ovarian development of yellow catfish. Higher-level dietary LNA/LA ratios are beneficial for HUFA -rich gonadal development and steroid synthesis of yellow catfish.