Effect of dietary soybean lecithin on fish performance, hemato-immunological parameters, lipid biochemistry, antioxidant status, digestive enzymes activity and intestinal histomorphometry of pre-spawning Caspian brown trout (Salmo trutta caspius).

A feeding experiment was conducted to evaluate the effects of dietary soybean lecithin (SBL) supplementation on performance, hemato-immunological parameters, lipid biochemistry, antioxidant status, digestive enzymes activity and intestinal histomorphometry of Caspian brown trout, Salmo trutta caspius in the pre-spawning stage. The basal diet was supplemented with 0% (control), 3%, 6%, 9% and 12% of SBL to obtain five experimental diets. Fish with an average weight of 350 ±â€¯10 g were randomly distributed among five experimental groups and fed for 90 days. Dietary SBL resulted in better performance including specific growth rate (SGR), weight gain (WG) and feed conversion ratio (FCR) (p < 0.05). Among the different hemato-immunological parameters, white blood cell counts (WBC), lysozyme, alternative complement activity (ACH50) and total immunoglobulin (IgM) content of serum were significantly increased with dietary SBL inclusion (p < 0.05). For antioxidant enzymes, glutathione S-transferase (GST) and catalase (CAT) showed significant differences among various experimental diets (p < 0.05). Furthermore, digestive enzymes activity including alkaline protease, lipase and amylase were increased in those fish received SBL supplemented diets (p < 0.05). Our results revealed that the dietary SBL improved some physiological responses of the fish and indicate 6-9% dietary SBL supplementation would improve the physiological competence of the pre-spawning Caspian brown trout breeders.

Semen characteristics of rainbow trout (Oncorhynchus mykiss) following diets containing different vegetable fatty acid levels.

Brood fish nutrition is an important factor susceptible to affect not only fecundity and gametogenesis but also gamete quality. In this study, we investigated the effects of altering dietary vegetable fatty acid content on semen quality (i.e. motility, density and seminal plasma composition), fertilizing ability and also blood testosterone (T) concentration in rainbow trout (Oncorhynchus mykiss). Fish were fed a commercial diet and ten formulated diets with similar proximate compositions but different levels of vegetable fatty acids (highly unsaturated fatty acids (HUFA): monounsaturated fatty acids (MUFA); HUFA: polyunsaturated fatty acids (PUFA); and HUFA: saturated fatty acids (SFA) ratios). Fish fed with HUFA: MUFA = 0.0 and HUFA: SFA = 0.25 ratios had the highest semen motility percentage and duration. However, the highest semen concentration and semenatocrit were observed in HUFA: SFA = 0.0 and HUFA: PUFA = 0.37 ratios. There was a significant difference in terms of K+ ion among diets supplemented with HUFA: PUFA = 0.0, HUFA: PUFA = 0.37 and HUFA: MUFA = 0.16 ratios (p < .05). Furthermore, Na+ ion showed significant difference between control group and diet supplemented with HUFA: PUFA = 0.0 (p < .05). Among the biochemical parameters, total protein showed a significant difference between HUFA: MUFA = 0.16 and HUFA: PUFA = 0.37 ratios (p < .05). No significant differences in fertilization ability and blood T concentration were found among dietary treatments (p > .05). In addition, the present data suggest that dietary fatty acid levels could affect semen quality but not fertilization ability in O. mykiss.