Effect of nettle (Urtica spp.), marigold (Tagetes erecta), alfalfa (Medicago sativa) extracts and synthetic xanthophyll (zeaxanthin) carotenoid supplementations into diets on skin pigmentation and growth parameters of electric yellow cichlid (Labidochromis caeruleus)

Abstract

This study was conducted to investigate the effects nettle (Urtica spp.), marigold (Tagetes erecta), alfalfa (Medicago sativa) plant extracts and synthetic carotenoid supplementations into diets (150 mg kg−1) on growth parameters and skin coloration of electric yellow cichlids. Five experimental groups included control, nettle, marigold, alfalfa and synthetic xanthophylls (Zeaxanthin; Zeax) treatments in 3 replications in 15 aquariums. Fifteen fish in each aquarium were fed ad-libitum (a total of 225 fish) twice a day for 3 months. Initial weight of the fish was 0.560 g. The weights were monthly measured and fish weights exceeded 2 g at the end of 3rd month (P > .05). The differences in weight gain, specific growth rate, feed consumption, total weight gain, feed conversion ratio and survival rate of the experimental groups were not found to be significant. The color parameters of L *, a *, b*, Hue and Chroma were calculated for all plant extracts. The greatest brightness (L*) value was obtained from the nettle extracts (61.850) and such a value was significantly different from the L* values of the control, zeax and marigold groups (P < .05). Hue (Hab°) angle at the end of the experiments was within yellow color in all groups. Hab° angle was calculated as 99.391° for alfalfa, 98.993° for marigold and 98.800° for nettle groups and they were greater than Zeax (94.881°) and Control (91.090°) groups (P < .05). The greatest chroma (Ch) was obtained from alfalfa extract (27.407) and differences in Ch values of the control and supplementation groups were found to be significant (P < .05). Obtained findings revealed that zeaxanthin supplementation as synthetic xanthophyll source and plant extract supplementations as natural carotenoid source yielded sufficient pigmentation on skin of electric yellow cichlids. Skin color of carotenoid-supplemented groups was brighter and purer as compared to the control group.