Effect of different forms of xanthophylls on body color of hybrid catfish (Silurus meridionalis Chen × Silurus asotus Linnaeus).

The objective of this study was to investigate the effect of four different forms of xanthophylls added in feeds on body color of hybrid catfish(Silurus meridionalis Chen×Silurus asotus Linnaeus).Five diets were prepared in the study,i.e.basal diet(control),basal diet supplemented with 200 mg/kg normal xanthophylls,200 mg/kg transformed xanthophylls,100 mg/kg coated-normal xanthophylls and 100 mg/kg coated-transformed xanthophylls,and fed to hybrid catfish for 20 days.The results indicated no significant differences in growth among treatments but the value of yellowness of the dorsal,ventral skin and xanthophylls content in skin,muscle of fish fed different xanthophylls were significantly higher than those of control(P0.05).The content of xanthophylls in dorsal and ventral skin of normal xanthophylls group were increased by 20.3 %,11.3 % compared with transformed xanthophylls group(P0.05).Pigmentation effect of 100 mg/kg coated-normal xanthophylls was similar to 200 mg/kg normal xanthophylls whereas 100 mg/kg coated-transformed xanthophylls was worse than 200 mg/kg transformed xanthophylls.We conclude that better pigmentation was obtained by adding normal xanthophylls than transformed xanthophylls and when the adding dose of coated-normal xanthophylls was half of normal xanthophylls,the pigmentation effect of former was same as the latter.