Ebrahim Sotoudeh

A feeding trial was carried out to evaluate the effects of inclusion of 3 (GL3), 6 (GL6), 9 (GL9), and 12 (GL12) % red seaweed, Gracilaria pygmaea, in rainbow trout, Oncorhynchus mykiss, feeds. A feed without seaweed was used as the control. All feeds were formulated to be iso-nitrogenous (48% protein), iso-lipidic (16%), and iso-energetic (20 kJ g?1), and they were fed to triplicate groups of 30 rainbow trout (initial average body weight 0.26 g) for 7 weeks. At the end of the trial, the final weight (FW) was significantly higher in fish fed the GL6 feed (3.49 ± 0.03 g) than that in fish fed the control (3.23 ± 0.03 g) and GL12 (2.85 ± 0.02 g) feeds (P < 0.05), but did not differ significantly from fish given the GL9 feed (3.30 ± 0.05 g). Moreover, specific growth rate (SGR) was significantly lower in fish fed the GL12 diet than that in other groups (P < 0.05). Feed intake (FI) showed a progressive increase with increasing Gracilaria levels. Feed conversion ratio (FCR) decreased up to a Gracilaria inclusion level of 6% (1.08 to 0.88) and then increased (1.12 in GL12). Supplementation of the experimental diets with G. pygmaea did not affect whole body composition and hematological parameters of juvenile rainbow trout (P > 0.05). In conclusion, the findings suggest that a dietary supplement of circa 6% G. pygmaea may be useful to promote the growth of juvenile rainbow trout.