each and find a control diet or one of two test diets supplemented with 1% OTP with two different mean particle sizes categorised as coarse (357 ?m) and fine (16 ?m) until 42 days of age. Treatments did not affect growth performance of ducks. Abdominal fat yield, subcutaneous fat thickness,intramuscular fat width and serum triglyceride (TG) concentration were reduced (P < 0.05)by fine but not coarse OTP. Both forms of OTP decreased (P < 0.05) drip loss of pectoralis major muscle, but only fine OTP increased (P < 0.05) superoxide dismutase (SOD) activity and decreased (P < 0.05) malondialdehyde (MDA) content in serum. In conclusion, fine OTP would be more effective in decreasing fat deposition and improving meat quality andantioxidant activity in meat ducks.