Depletion of stored nutrients during fasting in Nile tilapia (Oreochromis niloticus) juveniles

Authors: NEBO, CAROLINE - Universidade Estadual Paulista (UNESP); GIMBO, RODRIGO - Universidade Estadual Paulista (UNESP); KOJIMA, JULIANA - Universidade Estadual Paulista (UNESP); Overturf, Kenneth - Ken; DAL-PAI-SILVA, MAELI - Universidade Estadual Paulista (UNESP); PORTELLA, MARIA - Universidade Estadual Paulista (UNESP)

Submitted to: Journal of Applied Aquaculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/26/2017
Publication Date: 1/3/2018
Citation: Nebo, C., Gimbo, R.Y., Kojima, J.T., Overturf, K.E., Dal-Pai-Silva, M., Portella, M.C. 2018. Depletion of stored nutrients during fasting in Nile tilapia (Oreochromis niloticus) juveniles. Journal of Applied Aquaculture. 30(2):157-173. https://doi.org/10.1080/10454438.2017.1420516.
DOI: https://doi.org/10.1080/10454438.2017.1420516

Interpretive Summary: The effects of varying levels of soybean meal (SBM) and sunflower meal (SFM) incorporation in aquaculture feeds were investigated on growth, nutrient utilization, and the expression of genes related to the immune response in two commercial Canadian strains (strain 1 and strain 2) of Arctic charr. Five experimental diets with increasing levels of either SBM or SFM were fed to two Canadian strains of Arctic charr. Feeding these diets resulted in no changes in growth rate between the two strains. Increased levels of plant proteins in the diet negatively growth in both strains of fish. The effect of either soybean meal or sunflower meal was significant on the expression of certain immune genes in the fish these expression levels were higher in feeds with SBM than with SFM. Other measured factors, such feed intake and whole body composition, appeared to also be significantly affected by genetic strain. The difference in feed efficiency and whole body proximate composition for the two genetic strains of charr may indicate variations in efficiency for dietary energy utilization. This information will be useful in formulating sustainable feeds specific to aquaculture species and strains.

Technical Abstract: The effects of graded levels (0-20% total dietary inclusion) of commercial, solvent-extracted soybean meal (SBM) and expeller sunflower meal (SFM) were investigated on growth, nutrient utilization, and pro-inflammatory gene expression in the distal intestine and spleen of two commercial Canadian strains (strain 1 and strain 2) of Arctic charr. Five experimental diets with increasing inclusion of SBM or SFM were fed for 84 days to two Canadian strains of Arctic charr (initial body weight = 9g/fish). Feeding these diets resulted in no differences in growth rate (measured as final weight or thermal-unit growth coefficient, TGC) in the two strains. Increased inclusion level of plant proteins negatively affected FE (P<0.0001) with effects most commonly observed in groups fed SBM-based diets. The effect of the ingredient was significant (P<0.05) on PXR gene expression in the distal intestine; PXR expression was higher with SBM than with SFM. The effect of the inclusion level of plant ingredients was significant (P<0.05) on IL-Iß gene expression in the spleen. Feed intake, FE, NRE, ERE, whole body crude protein, lipid, gross energy, and organo-somatic indices (P<0.05) were significantly affected by genetic strain examined. Strain 2 exhibited higher FE and carcass crude protein content and lower carcass lipid content. The difference in FE, protein and lipid content for the two genetic strains of charr may indicate variations in efficiency for protein and lipid utilization, with a potential protein-sparing effect of dietary lipid noted in strain 2.