Abstract: 【Objective】 The objective of the experiment is to investigate the effects of different manganese (Mn) sources and levels on activities and mRNA levels of key enzymes in fat metabolism of broilers. 【Method】 An experiment was conducted using a completely randomized design involving a 2 × 2 plus 1 arrangement of treatments (two sources of Mn×two levels of added Mn plus a control with no added Mn). A total of 240 1-d-old Arbor Acres male broilers were randomly allotted by body weight into 5 treatments (8 replicate cages of 6 chicks per cage), and fed with a corn-soybean meal basal diet and a basal diet supplemented with 100 or 200 mg•kg-1 Mn as Mn sulfate (MnSO4•H2O) or Mn amino acid (Mn AA), respectively, for a duration of 42 days. 【Result】 Supplemental manganese did not affect (P＞0.10) the percentage of abdominal fat. However, the percentage of abdominal fat from broilers fed with diet with supplemental Mn tended to decrease (P=0.103). The activities of fatty acid synthase (FAS) and malate dehydrogenase (MDH) in liver and hormone-sensitive lipase（HSL）in abdominal fat were not affected (P＞0.10) by supplemental manganese source or the interaction between Mn source and level, but were influenced (P＜0.10) by supplemental Mn level. Chicks fed diets supplemented with 100 mg•kg-1 Mn from MnSO4•H2O or Mn AA had lower (P＜0.10) FAS activities in liver than those fed with control diet. Chicks fed diets supplemented with 100 or 200 mg•kg-1 Mn had lower (P＜0.01) MDH activities in liver than those fed with control diet, and there were no differences between the two Mn level treatments. Chicks fed diets supplemented with 200 mg•kg-1 Mn had higher HSL activities in abdominal fat than those fed with the control (P＜0.05) or 100 mg•kg-1Mn diet (P＜0.10), and there were no differences between the control and 100 mg•kg-1 Mn treatments. Supplemental Mn source or the interaction between Mn source and level did not influence (P＞0.10) mRNA levels of FAS and MDH in liver or FAS and LPL in abdominal fat, but supplemental Mn level affected (P＜0.01) MDH mRNA level in liver and did not influence (P＞0.10) other enzyme mRNA levels in liver and abdominal fat. As compared with the control, supplemental 100 or 200 mg•kg-1 Mn decreased (P＜0.01) MDH mRNA level in liver, and no differences were detected between the two Mn level treatments.【Conclusion】 Supplemental Mn could reduce abdominal fat accumulation by decreasing FAS and MDH activities in liver and increasing HSL activities in abdominal fat, and Mn might decrease MDH activity in liver by decreasing MDH mRNA level in it. There were no differences in the above effect between organic Mn and inorganic Mn.

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