Assimilation of dietary free
amino acids, peptides and protein in post-larval Atlantic halibut (Hippoglossus
hippoglossus)
C. R. Rojas-García, I. Rřnnestad-2003
Marine Biology, 142: 801-808
Abstract.
With the aim of improving the formulation of diets
for early stages of marine fish, post-larval Hippoglossus hippoglossus
(56 days after first feeding; 23 mg dry weight) were tube-fed
liquid diets of radiolabelled L-(14C) free amino acids (FAA
diet), peptides (PEPT diet) and protein (PROT diet), in order to compare the
kinetics of transfer from gut into the liver and carcass. The test diets
were prepared using equal concentrations of amino acids (AA) and fed as a
single pulse (0.3 µl, 2.2 µg AA). The PROT diet consisted of
methylated-14C-labelled (mainly lysine) bovine serum albumin
(BSA), the PEPT diet was the PROT diet digested with trypsin and the FAA
diet consisted of an amino acid mixture based on BSA composition with added 14C-lysine.
The common labelling with 14C-lysine permitted a comparison of
the three diets. Based on dissection and distribution of the tracer in each
compartment, the FAA diet was almost completely absorbed 1 h after the
tube-feeding; PEPT and PROT diets required more time before they were
processed by the digestive tract. The FAA diet was absorbed about eight
times as fast as protein and about six times as fast as peptides from the
gut. A low retention of label in the liver for all diets at all sampling
times suggests that the liver does not store the AA at these absorption
rates. The FAA diet had a higher assimilation efficiency (about 90%) than
the PEPT diet (about 12%) and PROT diet (about 32%). FAAs, thus, appear to
be superior to protein and peptides as a dietary source of amino acids in
post-larval Atlantic halibut.
(Department
of Zoology, University of Bergen, Allégt 41, 5007 Bergen, Norway, Tel:
+47-55583589, Fax: +47-55589673, E-mail: carlos.rojas@zoo.uib.no)