| Summary: | 碩士 === 國立屏東科技大學 === 水產養殖系所 === 104 === The study was aimed to investigate the effects of dietary phytic acid on organic and inorganic copper (Cu) utilization by juvenile hybrid tilapia (Oreochromis niloticus × O. aureus). In Experiment 1, the optimum dietary Cu levels were quantified for the species previously with organic (Cu amino acid complex) and inorganic Cu (CuSO4) as 10 mg Cu/kg and 4 mg Cu/kg, respectively. Casein-basal diet with 15 g/kg phytic acid was supplemented with optimum, 5×optimum and 10×optimum of organic Cu or inorganic Cu. Basal diet without phytic acid but supplemented with optimum levels of organic or inorganic Cu were also included for comparison. Total of eight experimental diets were each fed to triplicate groups of juvenile tilapia (mean initial body weight 0.99±0.01 g) for 8 weeks. Growth performance, whole body composition, immune responses, plasma ceruloplasmin activity and muscle and vertebral mineral concentrations were not affected (P>0.05) by dietary phytic acid supplementation, Cu sources or levels. In the organic Cu supplemented groups, fish fed the diet with 10×optimum Cu showed lower survival, hepatosomatic index (HSI) and hematocrit (Hct) than other dietary treatments. Whole body and hepatic Cu concentrations increased with the increment of dietary Cu levels regardless of Cu sources. Result indicated that dietary phytic acid (15 g/kg) did not affect growth performance, physiological responses and tissue mineral concentrations of tilapia. In Experiment 2, soybean meal-basal diet (containing 6.9 mg Cu/kg and 15.8 g/kg of phytic acid) were supplemented with 4, 8 and 12 mg Cu/kg of organic or inorganic Cu. Basal diet without Cu supplementation was used as control. Total of seven experiment diets were each fed to triplicate groups of juvenile tilapia (mean initial body weight 0.73±0.01 g) for 8 weeks. There were no significant difference in growth performance, hematological indices, immune responses, plasma ceruloplasmin activity, whole body composition and hepatic Cu concentration of tilapia regardless of Cu sources or levels. Whole body Cu concentration was not affected by dietary Cu sources, but increased with increasing dietary Cu levels. Results indicated that the phytic acid derived from soybean meal did not influence the utilization of organic and inorganic Cu by tilapia. The Cu concentration in soybean meal-basal diet (6.9 mg Cu/kg) can meet the Cu requirement for tilapia. Overall of the two experiments, dietary phytic acid does not affect the utilization of organic and inorganic Cu by tilapia.
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