| The present study selected xanthophylls from marigold(Tagetes erecta) as test comound, yellowcatfish (Pelteobagrus fulvidraco) as target animal to research the efficacy and safety of xanthophyllsapplied in aquatic feed as a feed additive by three experiments.1)To obtain loss of natural xanthophyllsafter extrusion process and water stability;2)To study the impacts of natural xanthophylls from marigoldon growth performance, skin coloration, hematological parameters and serum antioxidant profiles andhistological structure of liver;3)To study the bioaccumulative and metabolic regulation in tissue ofyellow catfish. The results were respectively as follows:1. Xanthophylls from marigold with total xanthophylls content as4.64%, including about4.00%luteinand0.19%zeaxanthin were tested in the studies. Five experimental diets were formulated with0%,0.15%,0.3%,0.6%,8%xanthophylls were mixed uniformly and made into2mm extruded pellets.The process condition were feeding section:90℃5s, conpression section:130℃3s and meltingsection:60℃4s. The additive theoretical value of natural xanhophylls from marigold was0,69.6,139.2,278.4,3700mg/kg and the determined value of the five diets were0,24.2,54.2,118and1700mg/kg andwere named as C, L24.2, L54.2, L118, L1700, respectively. The loss rate of xanthophylls was43.40%.The diets of C, L24.2, L1700with5reduplicates were used to determine the water stability ofxanthophylls at30min,1h,2h,24h, respectively. The results showed that99%of xanthophylls were lostin solution into30min.We suggest that xanthophylls from marigold was only suitbable to the fastfeeding fish.2. A90-day was conducted to evaluate the efficacy of xanthophylls from marigold on yellow catfish(Initial body weight:21.00±0.01g). The results showed that no significant differences were found onSR among groups. SGR and feed efficiency of L24.2, L54.2, L118, L1700, PPV of L24.2, EPV of L54.2,L118, L1700were significantly higher than those of C group (p<0.05). Yellowness (b~*) and saturation(C~*) of lateral and ventral skin obviously increased with higher xanthophylls inclusion level andreached saturation value in L118, which showed no difference with L1700group (p>0.05).Pigmentation in skin deposited excessively and transferred into muscle. Bioaccumulation factor showeda parabolic relationship with the dietary xanthophylls levels, and highest BCF was observed with76.25mg/kg of xanthophylls in diet. Serum CHO was linary increased with the dietary xanthophylls levels(P<0.05), and HDL-C of L1700was significantly higher than that of C group. Histological of liver inL24.2, L54.2, L118, L1700were not found any structure abnormal. According to the Regulation of ECNo1831/2003and70/524/EEC and the efficacy of xanthophylls as above, we suggest that therecommented highest level for xanthophylls from marigold in fish diets should be no more than100mg/kg, as safety factor of17-fold.3. A depositon and withdrawal experiments on xanthophylls in yellow catfish(21.00±0.01g) wasconducted. The skin and muscle samples were taken at the7th,14th,21th,28th,42th and56th day fordeposition and the9th day for withdrwal. Xanthophylls were not stablely deposted in fish skin fed with dietary xanthophylls level at24.2mg/kg. But the deposition of xanthophylls in skin fed diets L54.2,L118, L1700were constantly increased during56days’ feeding period and did not decreasesignificantly after9d elimination. The peak value was found in fish muscle for groups of L24.2, L54.2and L118at35d while that of L1700was at42d. Skin was the main organ used to deposit xanthophyllsin yellow catfish and could deposite continuously xanthophylls from marigold what yellow catfishcould digested, muscle was the organ for temporary storage. |
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