An optimum level of vitamin
A supplements for Atlantic halibut (Hippoglossus hippoglossus L.)
juveniles
M.
Moren, I. Opstad, M.H.G. Berntssen, J.-L. Zambonino Infante, K. Hamre-2004
Aquaculture, 235(1-4): 587-599
Abstract:
Six diets with different levels of retinyl acetate
were fed in triplicate to Atlantic halibut larvae for 13 weeks. The dietary
levels used were 0, 0.25, 0.75 (National Research Council (NRC)
recommendation), 2.5, 25 and 250 mg retinol equivalents (RE) kg−1
diet (in dry weight). Any sign of deficiency or toxicity was recorded and
analysed. No differences in mortality or weight gain were observed among the
groups, although the groups fed 0 or 0.25 mg RE kg−1 diet
had external haemorrhages and a reduced growth in length. Levels of retinol
(ROH), didehydro retinol (dd-ROH), retinyl esters (ROHes) and didehydro
retinyl esters (dd-ROHes) were analysed using HPLC equipped with a diode
array detector. Between the groups fed 0–0.75 and 2.5–250 mg RE kg−1
diet, there was an overall change in retinoid levels from being indifferent
to increasing exponentially. Groups fed 2.5 mg RE kg−1 diet
had the highest specific activity in two brush border membrane (BBM)
enzymes, indicating that the fish fed this diet had a highly developed or
differentiated intestinal mucosa. Furthermore, DNA levels were lower in the
groups fed 0.75–25 mg RE kg−1 diet (dry weight), while
the other groups of fish showed higher proliferation of cells. This
proliferation was confirmed by immunohistochemistry using proliferating cell
nuclear antigen (PCNA). The results indicated that the optimum level of
retinoids in the diets for Atlantic halibut juveniles was closer to 2.5 mg
than the recommended 0.75 mg RE kg−1 diet. Our
recommendation is to use 2.5 mg RE kg−1 diet but not more
because retinoids are shown to be toxic in excess.