Abstract
This work studies final nutritional status and transcriptional responses of rainbow trout (Oncorhynchus mykiss Walbaum 1792) (28 g) after a 10 week feeding experiment designed to elucidate the effect of adding a vitamin and mineral premix on growth, health, and nutritional endpoints. Juvenile fish were fed a either a diet supplemented with a vitamin and mineral premix (Diet S) or the same diet without premix supplementation (Diet U). The analyzed micronutrient composition of diets differed accordingly. Pooled livers from 15 fish from each dietary group were used to create suppression subtractive hybridization (SSH) cDNA libraries that were sequenced with 454 FLX GS Titanium Technology. In total 552 812 reads were sequenced from the two cDNA libraries. Ingenuity pathway analysis (IPA) was then used to characterize the hepatic transcriptome of the two dietary groups of rainbow trout. In the present communication we discuss how selected micronutrients may affect the transcriptome at suboptimal status by directly impacting the cellular metabolism, functions, and structures, and by introducing respective compensatory mechanisms. Processes related to lipid metabolism, peptide hydrolysis, oxygen transportation, and growth development were mostly affected. Considering the transcriptomics data relative to changes in nutritional status from the feeding study and the background phenotypic outcome of growth performance and gill histopathology, the outcome of the transcriptional profiling are suggested to be mainly related to suboptimal pantothenic acid and vitamin C nutrition.
Highlights
It is generally acknowledged that the limited global fish meal and fish oil production cannot support the future growth in aquaculture, so there is a need for large and stable supplies of suitable alternatives, like selected plant proteins and lipids [1,2]
Dividing the feeding experiment into 5 weeks intervals indicated no difference in the first period (Diet U: 3.0760.03% day21; Diet S: 3.0860.05% day21; n = 3), while a reduced specific growth rate were observed in the second period for fish fed the diet without premix supplementation (Diet U: 1.9160.08% day21; Diet S: 2.0860.03% day21; n = 3; p,0.05)
The biological performance was seemingly not different between the two diets in the present study, with just a minor growth depression in rainbow trout fed the unsupplemented diet during the second half of the experiment
Summary
It is generally acknowledged that the limited global fish meal and fish oil production cannot support the future growth in aquaculture, so there is a need for large and stable supplies of suitable alternatives, like selected plant proteins and lipids [1,2]. High fishmeal and fish oil replacement levels have successfully been adopted, with increasing concern that the modern diets do not fulfill the requirements of all essential nutrients. It is a constant need for more and better knowledge on nutritional requirements for farmed fish. Traditional feed formulations with use of fishmeal (proteins) and oils (lipids) contained enough of most micronutrients needed by the fish. Vitamin and mineral premixes are concentrates of stable forms of essential vitamins mixed with essential elements in carriers, added to feeds separately. Mineral premixes are concentrates of essential elements, often added in surplus levels to ensure that potential antagonistic interactions among feed ingredients are avoided. Among the supplemented trace elements in salmonids diets are manganese, iodine, copper, zinc and iron [2,4]
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