Effect of Water-Soluble Polysaccharides Extracted from Microalge (Spirulina platensis) on Growth Performance, Body Composition and Immune Response of Rainbow Trout (Oncorhynchus mykiss)

This experiment evaluated the effect of soluble polysaccharides in Spirulina platensis microalgae on growth performance, body composition and immune response of rainbow trout (Oncorhynchus mykiss). In this regard, 180 rainbow trout (17.22 ± 0.5g) were selected and distributed in five experimental treatments (with three replications). Treatments included different levels of polysaccharide in dosage of 0 (control), 500, 1000, 2000 and 3000 mg / kg of feed. According to the results, in growth factors (final weight, body weight gain, specific growth factor, protein efficiency, feed conversion ratio and condition factor), no significant difference was observed. The highest and the lowest amount of carcass proteins were observed in the diet containing 500 mg polysaccharide and control, which showed a significant difference. The amount of fatty acids of the muscle of the fish body did not show any significant difference among the treatments. The highest and lowest levels of lysozyme activity were observed in treatments of 2,000 mg polysaccharide and control and the highest and lowest levels of complement activity were observed in treatments containing 3000 mg polysaccharide and control respectively (P <0.05). In general, the use of polysaccharide extracted from micro-algae did not significantly improve rainbow trout growth, but a slight improvement in growth and body composition (protein) in 500 mg polysaccharide per kg of diet was observed. In terms of safety indicators, treatments of 2,000 and 3,000 mg of polysaccharides per kg of diet had a good performance and could be used whenever needed.