Skin colour changes in ornamental koi (Cyprinus carpio) fed different dietary carotenoid sources
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Date
2006
Authors
Tan, Phaik Shiang
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Abstract
Koi value increases with intensity of skin colour. Fish coloration and
pigmentation is due to absorption and deposition of carotenoids. Fishes are
unable to synthesize their own carotenoids and therefore these must be
included in their diet.
Three trials were undertaken to investigate skin colour changes in
ornamental koi (Kohaku) by feeding a dietary carotenoid supplement of algal
(Haematococcus pluvialis or Spirulina) or palm carotenoid (powder and oil
form). Diets containing synthethic carotenoids (Astaxanthin or Canthaxanthin)
and a control diet with no carotenoids added were used for comparison.
In the first experiment, koi (12.89 + 0.02g) were fed diets supplemented
with carotenoid sources at a level of 100ppm. The experiment was conducted
in a static water system for a period of 10 weeks. Koi fed with diets
supplemented with carotenoids exhibited better body coloration than those fed
the control diet without added carotenoids. Growth performance of koi were
affected by the dietary carotenoids source. Koi fed diets supplemented with
spirulina or Carosol respectively, showed higher growth than koi fed other diets.
There were differences (P< 0.05) in skin total carotenoid and individual
carotenoid types in the skin, muscle and liver of koi. The total carotenoids on
the skin of koi fed with Spirulina or Carophyll Pink supplemented diets showed
significantly higher value, 12.08mg kg-1 and 11.76mg kg-1, respectively. Visual
observations of the morphology of chromatophores on the scale of koi fed with
different diet were done under high power light microscope.
In the second experiment, koi (254.89 + 16.82g) were fed diets fortified
with carotenoids at a level of 250ppm or 500ppm, respectively. The experiment
was conducted in static water system for a period of 8 weeks. Growth
performances of koi were not affected by the addition of carotenoids to their
diet. Koi fed added dietary carotenoids exhibited better body coloration than koi
fed the control diet with no added carotenoids. Colour parameter such as L*, c*
and h* were measured using a Minolta Colour Reader (CR-100) at three
different colour regions (white, orange and red) on the koi body. Based on the
CIELCH colour scale (CIE, 1976), L* indicates Lightness, C* indicates chroma
and h* indicates the hue angle. Koi fed diets supplemented with 500ppm
Carophyll Pink or Spirulina increased their redness. Some of the head region of
koi fed carotenoids supplemented at 500ppm turned yellowish and this
indicated an overdose of dietary carotenoids. There were significant differences
(P< 0.05) in total carotenoid and individual carotenoid types deposited in koi
gonad and blood serum. The total carotenoids concentrations in blood serum
and gonad of the koi fed 250ppm Spirulina supplemented diet were the highest.
In the third experiment, koi (49.36 + 0.32g) were fed diets fortified with
carotenoid sources at a level of 250ppm in a water flow through system for a
period of 12 weeks. Growth performances of the koi were not affected by the
addition of carotenoids to their diet. There were no significant differences (P>
0.05) in total carotenoid on the skin of all the koi. However, there were
significant differences (P< 0.05) in individual carotenoid types of koi fed different
diets. The astaxanthin content of koi fed diets supplemented with 250ppm
Carophyll Pink was significantly higher than diet supplemented with 250ppm
Carophyll Red or Caromin throughout the feeding trial. Colour parameter (L*,
a*, b*, c* and h*) were measured at the left dorsal regions. L* indicated
Lightness, a* indicates red-green chromaticity and b* indicates yellow-blue
chromaticity (CIELAB, 1976). There were significant differences (P<0.05) for L*
and b* of koi skin. In conclusion, certain dietary carotenoids may affect or
increase the growth performances and colouration in koi. Koi pigmentation
depends on proper carotenoid source (synthetic or algal) with suitable
carotenoid levels (100-250ppm) and appropriate feeding period (8-12 weeks)
which are the crucial factors for better colouration and growth performances of
koi.
Description
Master
Keywords
Biological Science , Ornamental koi , Carotenoid