Effects of dietary phytic acid on organic and inorganic zinc utilization in juvenile hybrid tilapia (Oreochromis niloticus × O. aureus)

• Main Authors: Hsi-Yuan Chen, 陳熙元
• Other Authors: Shi-Yen Shiau
• Format: Others
• Language: zh-TW
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/87240712384539283767

碩士 === 國立臺灣海洋大學 === 食品科學系 === 100 === The purpose of this study was to elucidate the effects of dietary phytic acid on zinc (Zn) utilization in juvenile hybrid tilapia (Oreochromis niloticus × O. aureus). The optimum dietary Zn requirements (NZn) was quantified for the species previously with organic Zn (Zn amino acid complex, Zn-AA) and inorganic Zn (ZnSO4) as 10 mg Zn/kg and 30 mg Zn/kg, respectively. In this study, basal diet with 1.5% phytic acid was supplemented with optimum, 5X optimum and 10X optimum level of Zn-AA or ZnSO4; basal diet without phytic acid but supplemented with either optimum Zn-AA or optimum ZnSO4 were included as comparison. There were total eight experimental groups, each was fed to triplicate groups of tilapia (mean initial body weight 1.43±0.02 g) for eight weeks. In the inorganic Zn supplementation groups, fish fed the diet without phytic acid supplemented with optimum Zn had significantly (P<0.05) higher weight gain and hepatic Zn concentration than fish fed diet with phytic acid; fish fed diet with phytic acid supplemented with 10X-NZn had higher plasma lysozyme activity and red blood cell (RBC) count than the other dietary treatments; fish fed diet without phytic acid supplemented with NZn and diet with phytic acid supplemented with 10X-NZn had higher superoxide anion production ratio, plasma zinc concentration and white blood cell (WBC) than fish fed diet with phytic acid supplemented with NZn; Copper-zinc superoxide diemutase (CuZn-SOD) activity were similar in all dietary groups. In the organic Zn supplementation groups, weight gain, WBC, RBC, plasma and whole body Zn concentration, superoxide anion production ratio and plasma lysozyme activity were similar in all dietary groups; fish fed diet with or without phytic acid supplemented with NZn had lower hepatic Zn concentration than the other dietary groups; fish fed diet without phytic acid supplemented with NZn had higher copper-zinc superoxide diemutase (CuZn-SOD) activity than fish fed diet with phytic acid supplemented with NZn. Feed efficiency, protein efficiency ratio and hepatosomatic index of the fish were not different regardless of Zn source or supplementation level. Diet containing phytic acid at NZn supplementation level, fish fed diet with Zn-AA had higher WBC, RBC, Hct and Hb concentration, whole body Zn, magnesium and iron concentrations, superoxide anion production ratio and plasma lysozyme activity than fish fed diet with ZnSO4. This study demonstrates that tilapia fed diet with 1.5% phytic acid decrease inorganic zinc (ZnSO4) utilization, increasing Zn supplementation level (10X ZnSO4) may offset the phytic acid lowering Zn utilization effect; at optimum Zn supplememtation level, organic Zn is better utilized than inorganic Zn.