The effect of dietary pigments on the coloration of Japanese ornamental carp (koi, Cyprinus carpio L.)

Abstract

This study evaluated the effects of dietary supplementation with four pigment sources on the coloration of Japanese ornamental carp (Showa koi) (Cyprinus carpio L.). Showa koi (which are colored black with scattered red patches and white spots) initially weighing 18.04±0.92g were fed five dietary treatments in triplicate: a control diet with no added pigments, a diet with 1.5gkg⁻¹ Carophyll® red (synthetic, CR diet), a diet with 200gkg⁻¹ wet weight of a photosynthetic bacterium (Rhodopseudanonas palustris, PB diet), a diet with 200gkg⁻¹ wet weight of effective microorganisms (EM diet) and a diet with 75gkg⁻¹ dry weight feed-grade Spirulina platensis (SP diet). After a 99day feeding trial, the fish's color was evaluated with a colorimeter to measure the chroma, lightness, redness and yellowness of different color zones. The carotenoid and xanthophyll concentration in the skin and the scales of the fish's red, black and white zones were tested. S. platensis significantly increased the growth and feeding efficiency of koi (P<0.05). S. platensis and Carophyll® red significantly improved the chroma of the black zone, the redness and the chroma of the red zone, and the lightness of the white zone (P<0.05). S. platensis and Carophyll® red increased the carotenoid content of the black and red scales and the xanthophyll content of the black and red skin and scales (P<0.05). The results indicate that Showa koi pigmentation can be modified by supplementing the diet with 1.5gkg⁻¹ Carophyll® red or 75.0gkg⁻¹S. platensis. Dietary R. palustris, at levels up to 1.0gdrymatterkg⁻¹ of diet, does not appear to affect the coloration of Showa koi. Furthermore, body coloration was generally correlated with the dose of dietary carotenoids and xanthophylls, and carotenoids had a deeper and greater influence than xanthophylls.