Digestive efficiency,free amino acid pools and quality of growth performance in Atlantic salmon (<Emphasis Type="Italic">Salmo salar</Emphasis> L.) affected by light regimes and vaccine types |
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| Authors: | Krisna Rungruangsak-Torrissen Jan Sunde Arne Erik Berg Ulla Nordgarden Per Gunnar Fjelldal Frode Oppedal |
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| Institution: | (1) Institute of Marine Research, Matre Research Station, 5984 Matredal, Norway;(2) Present address: Geno, 2326 Hamar, Norway |
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| Abstract: | This study comprised the results of three different seawater trials using unique combination of techniques to study protease
digestive efficiency and growth performance quality to illustrate the effects of light regimes and vaccine types in Atlantic
salmon (Salmo salar L.). Fish with higher growth had higher trypsin (T) and chymotrypsin (C) specific activities with higher T/C ratio or slope
T/C ratio calculated from the regression between trypsin (y) and chymotrypsin (x) specific activities] in the pyloric caeca. The T/C ratios indicated fish growth rates over a period of 1–2 months, while
the slope T/C ratios indicated fish growth rates at sampling. Adaptation period for adjustment to the new environment of continuous
light was 70 days, indicated by the differences in trypsin specific activities and the crossing of slope T/C ratio regressions
following with the changes in growth rate directions between the control and the treated group. Vaccine types affected fish
vertebral growth, and additional continuous light enhanced the impact of vaccines on fish growth during springtime, indicated
by differences in slope T/C ratios. Continuous light stimulated fish growth during winter to spring, when the natural day
length was short, without significantly changing white muscle and oocyte qualities in the fish of about 500 g, except for
significantly increased white muscle RNA concentration. Continuous light also reduced fish growth rate later during summer,
when the natural day length was long, by precedently decreasing the T/C ratio in late spring. Interestingly, plasma levels
of free lysine related to tryptic digestion were correlated with trypsin specific activity levels. Continuous light caused
higher levels of most free amino acids (FAA) involved in nitrogen metabolism, higher incorporation of essential FAA for protein
synthesis, and higher protein turnover rate (free hydroxyproline levels) in both plasma and white muscle. However, continuous
light did not affect higher protein content, intracellular buffering capacity and RNA levels in the white muscle of the fish
of about 1 kg, probably due to limitation of FAA available for protein synthesis. It is therefore suggested that enhancing
fish growth by continuous light stimulation should be accompanied by increasing availability or content of dietary protein
(and probably minerals), which in turn would improve the quality of fish growth performance through increasing fillet protein
concentration, strengthening vertebral growth, and delaying oocyte development. |
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| Keywords: | Free amino acids Hydroxyproline Lysine Oocytes Plasma RNA RNA/protein ratio Slope T/C ratio Trypsin Trypsin/chymotrypsin (T/C) ratio White muscle |
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