Rare earth elements have been widely used in agriculture in China, European and American. Besides the application of rare earths in farming, rare earths are also used in livestock to: increase productivity, reduce food costs, reduce disease and mortality, and increase food quality. According to the previous reports, the effective of using organic rare earth compounds were better than inorganic compounds. Its has been evaluated by field tests. The parameters of citrate complexes synthesis are as follows: 4M citric acid, reaction pH is 3, reaction temperature is 80oC, reaction time is 5h, molar ratio citric acid/RE3+(M/M) is 1.25. The parameters of ascobate complexes synthesis are as follows: 2M ascorbic acid, reaction pH is 3.5, reaction temperature is 80oC, reaction time is 6h, molar ratio ascobic acid/RE3+(M/M) is 3.25, the synthesis efficiency is nearly 95%.This report also presents the results of trials evaluating the effectiveness of ascorbate complexes added to catfish feed and rare earth citrate added to chicken feed: The results show that rare earth citrate is added at a low level, 200 mg/kg feed reduced diarrhea rate by 33.58%, reduced respiratory disease rate by 26.73%, increased weight gain rate by 5.51%, daily weight gain by 5.64% and decreased feed conversion ratio by 5.7%. Similar to the results of catfish, additions with rare earth ascorbate complex at 200 mg/kg feed helped improve weight gain by nearly 12% compared to the control (p<
0.05) after 56 days
Reduced FCR by nearly 7% compared to the control after 84 days
increased survival rate by about 7% compared to control. Rare earth residues in food are not much different from the control.