Inclusion of fructooligosaccharides and mannanoligosaccharides in plant-protein based diets for rainbow trout (Oncorhynchus mykiss) fingerlings and its effects on the growth and blood serum biochemistry

ABSTRACT Background: Plant-origin proteins are alternatives to substitute the fishmeal in diets for aquatic organism, but their use might require the supplementation of prebiotics, non-digestible components that are metabolized by the intestine microbiota of the host. Goals: To evaluate the effects of inclusion of fructooligosaccharides (FOS) and mannanoligosaccharides (MOS) to diets with plant protein concentrates for fingerling of rainbow trout (Oncorhynchus mykiss). Methods: A basal diet with soy, rice and corn protein concentrates (234, 241 and 170 g/kg, respectively) was supplemented with FOS (D-FOS) and MOS (D-MOS) with 30 g/kg. The basal diet was the control (D-Control), and a commercial diet (Comm) was also used. Diets were fed to triplicate groups of fingerlings of an initial weight of 1.75 ± 0.03 g (mean ± standard error). After 60 days, the growth performance was determined and samples for contents protein and lipids in muscle and liver were taken, as well, samples of blood for serum contents of protein, glucose, and triglycerides. Results: No significant differences were observed in the growth performance among the treatments. Protein content in muscle did not show significant differences; significantly higher values were observed in the protein liver contents of Comm. Lipid contents in liver did not show significant differences, but significantly higher lipid content was observed in the D-MOS for muscle. Contents of serum protein were significantly lower in the Comm and serum triglycerides were significantly higher in the same diet. Conclusions: Regardless the inclusion of FOS and MOS, the results indicate the possibility to use the diets without affecting the growth and wellness of rainbow trout fingerlings, but more research is necessary regarding the possible effects of lipids on liver and muscle.