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http://hdl.handle.net/1956/2436
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| Title: | Challenges related to delivery of water soluble nutrients to marine fish larvae : evaluation of changes in nutritional quality due to production process and leaching from larval diets -with emphasis on protein quality |
| Authors: | Nordgreen, Andreas H. |
| Issue Date: | 26-Jun-2007 |
| Publisher: | The University of Bergen |
| Abstract: | Marine fish larvae fed formulated diets have suppressed growth and survival compared to
larvae fed live feed for the first weeks. Live feed is successfully used in the aquaculture
industry, although there are difficulties delivering controllable concentrations of several
nutritional compounds. In research, the use of formulated diets is therefore essential to
accomplish proper nutritional dose response studies. The focus of this work was to study the
properties of a protein cross-linked diet and a heat coagulated diet used for nutritional studies
of marine fish larvae. The ability to deliver water soluble nutrients and changes in protein
quality due to production processes and exposure to leaching was emphasized. A pancreatic
protein in vitro digestibility method, simulating stomachless fish larvae, was used to
investigate the digestibility of various live feeds and feed ingredients. The same in vitro
model was also used to study the effect of the production processes and the effect of increased
inclusion of hydrolyzed protein in compound diets.
Both diets showed substantial changes in protein quality due to the production process and
exposure to leaching. The protein cross-linked capsules had a nearly complete loss of watersoluble
nitrogen (N) during cross-linking and the following washing steps and more than 90
% loss of other water-soluble micronutrients. The protein cross-linking led to a 25 %
reduction in in vitro protein digestibility. A large fraction of the soluble N in the feed
ingredients was made insoluble by heat denaturation during production of the heat coagulated
diet, but the concentrations of peptides and free amino acids (FAA) were not influenced.
However, after exposure to leaching for 6 min most of the soluble N fraction was lost and
there were no significant difference in concentrations of soluble N between diets with
increasing concentration of hydrolyzed protein ranging from 0 % to 45 % of total protein.
There were no significant differences in in vitro digestibility between the four diets with increasing concentration of hydrolyzed protein. However, the leached diets showed
significantly reduced digestibility compared to the diets that had not been exposed to
leaching. In conclusion, neither the protein cross-linked nor the heat coagulated diet may be
suitable for the delivery of water-soluble nutrients to marine fish larvae.
The protein in vitro digestibility of the protein cross-linked diet, heat coagulated diets and a
commercial larval diet (53 – 73 %) were lower than frozen live feed (84 – 87 %). The
digestibility of the soluble N fractions was similar for the marine meals and the live feed and
higher than the respective insoluble protein fractions. However, the live feed contained 54-67
% soluble N in comparison to the marine meals that only contained 11-17 % soluble N.
In the search for other possible diets to deliver soluble nutrients, lipid spray beads (LSB) were
investigated. LSB, as part of complex particles, has been an interesting candidate for
delivering soluble nutrients with a high retention efficiency, although the fatty acid profile of
the LSB have made them inappropriate when delivered in large quantities. LSB with an
improved fatty acid profile were developed by inclusion of high concentrations of
phospholipids. Due to the hydrophilic behavior of phospholipids, the LSB dispersed in water
and could therefore be used to deliver water soluble micronutrients to live feed. The riboflavin
content of Artemia was increased from 55 ± 0.6 mg kg-1 (dw) to 329 ± 62 mg kg-1 (dw) after 1
h enrichment. There is still a severe leaching rate of highly soluble nutrients and the LSB
might therefore not be able to deliver nutrients needed in large quantities such as FAA and
peptides. However, for nutrients needed in small quantities, the LSB seems to be a promising
tool. |
| URI: | http://hdl.handle.net/1956/2436 |
| ISBN: | 978-82-308-0400-1 (print version) |
| Appears in Collections: | The National Institute of Nutrition and Seafood Research (NIFES)
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