Effects of Hibiscus rosasiensis as a natural carotenoid on growth performance, body composition, pigmentation and carotenoid in blood plasma of blue gourami, Trichogaster trichopterus at different stocking densities

This study examined the effects of China rose powder (Hibiscus rosasiensis) supplementation (1.5%) on the growth performance, body composition, and pigmentation of blue gourami at different stocking densities (0.6 and 0.9 fish L-1). Four treatments were assigned in this study: China rose diet+0.6 fish L-1 (CG0.6), China rose diet+0.9 fish L-1 (CG0.9), control diet+0.6 fish L-1 (C0.6) and control diet+0.9 fish L-1 (C0.9). The results showed that after 70 days, there were no significant differences in growth and body composition between China rose treated groups and their corresponding control groups. Color parameters (L*Lightness, a*redness, b*yellowness) behind the operculum were measured on a weekly basis. Results indicated that in the most of weeks, there were no significant differences for (L*, a*, b*). However in the China rose treatments, the fish were brighter in the first weeks but turned darker in the last weeks. The fish in the China rose treatments had higher greenness and yellowness values at the end of the experiment. The amounts of skin total carotenoids, canthaxanthin and β-carotene in the China rose groups were significantly different compared with the corresponding control groups. Similar patterns were observed in muscle and caudal fin canthaxanthin and β-carotene contents. Significant differences were observed in the content of blood plasma canthaxanthin and β-carotene between C0.6 and CG0.6; whereas such differences were observed in astaxanthin, canthaxanthin and β-carotene between C0.9 and CG0.9 groups. The study shows that the China rose powder is a potent natural carotenoid source for blue gourami to enrich its color in low density.