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Effects of dietary supplementation with red seaweed, Gracilaria pygmaea, on growth, carcass composition and hematology of juvenile rainbow trout, Oncorhynchus mykiss

Sotoudeh, Ebrahim, Jafari, Marziyeh
Aquaculture international 2017 v.25 no.5 pp. 1857-1867
Gracilaria, Oncorhynchus mykiss, body composition, body weight, carcass composition, experimental diets, feed conversion, feed intake, feeds, fish, hematologic tests, hematology, juveniles, macroalgae, protein content, specific growth rate
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.