M. Yazdanpanah - Department of Fisheries, Faculty of Agriculture and Natural Resources, Persian Gulf University, Bushehr, Iran
E. Sotoudeh - Department of Fisheries, Faculty of Agriculture and Natural Resources, Persian Gulf University, Bushehr, Iran
H. Mansouri Taee - ۲Lorestan Fisheries Adminestration, Khoramabad, Iran
H. Habibi - Department of Animal Husbandry, Faculty of Agriculture and Natural Resources, Persian Gulf University, Bushehr, Iran

This study investigated the effect of Sargassum angustifolium and Gracilaria pulvinata extracts on the growth performance, body composition, antioxidant status and gut microbiota of rainbow trout (Oncorhynchus mykiss) fry. For this purpose, ۵۴۰ fry of rainbow trout (initial weight ۰.۲۳±۰.۰۴ g) were distributed in ۱۲ fiberglass tanks. Fish were fed with experimental diets containing ۵۰۰ mg kg-۱ of Sargassum extract (SA), ۵۰۰ mg kg-۱of Gracilaria extract (GL) and ۲۵۰ mg kg- Sargassum + ۲۵۰ mg kg-۱ Gracilaria extract (SA+GL). The control diet was a commercial diet without seaweed extract. At the end of experiment growth and feeding performance including final weight, specific growth rate (SGR), weight gain (WG) and feed conversion (FCR) in all treatments were not significantly different (p > ۰.۰۵). Whole body protein, ash and moisture contents of fish were not significantly affected by dietary macroalgae extracts (p > ۰.۰۵). However, lipid content was significantly lower in fish fed of extract Gracilaria and Sargassum compared to control (p < ۰.۰۵). The seaweed extract-fed fish utilized efficiently the body lipid and suppressed body weight loss during starvation. No significant difference (p > ۰.۰۵) in serum total protein, creatinine alanine transaminase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP) and blood superoxide dismutase (SOD) activity were observed in all treatments. Whereas serum albumin, glutathione peroxidase (GPX) and catalase specific activity were higher in SA, GL and  SA+GL treatments compared to the control group (p < ۰.۰۵). ACH۵۰ level was significantly (p > ۰.۰۵) increased in GL and SA+GL treatments as compared SA and control group. The addition of Sargassum and Gracilaria extracts to feed did not affecte total bacterial population but increased lactobacillus bacteria levels (p < ۰.۰۵) in the intestine. These results revealed the potential antioxidant enhancing and health-promoting effects of dietary Sargassum angustifolium and Gracilaria pulvinata extracts.  

Macroalgae extract, Immunostimulant, Bacterial population, Antioxidant status, Rainbow trout