肉牛血浆和尿液中莱克多巴胺残留消除规律分析

【目的】研究莱克多巴胺在肉牛血浆和尿液中的残留消除规律.【方法】选取3头中国‘西门塔尔’杂交肉牛,连续饲喂莱克多巴胺28d,给药剂量2.01mg/(kg·d),采集给药第1、7、14、21、28d和停药第3、7、14、28d血浆和尿液样品,采用高效液相色谱串联质谱法(HPLC-MS-MS)检测血浆和尿液中莱克多巴胺含量.【结果】血浆与尿液中莱克多巴胺含量均在给药7d达到峰值,血浆中残留量为(6.55±1.93)ng/mL,未酶解尿液中残留量为(8 402.03±1 307.09)ng/mL.峰值之后莱克多巴胺含量开始下降,停药后下降迅速,停药3d时血浆中残留量为(0.60±0.01)ng/mL,未酶解尿液中残留量为(1 334.93±25.74)ng/mL,停药28d时血浆中未检测到莱克多巴胺,而未酶解尿液仍可检测到(5.77±0.10)ng/mL;酶解后尿液中莱克多巴胺含量显著高于酶解前(P0.05).【结论】与血浆相比,肉牛尿液更适合作为莱克多巴胺的监管靶标.

Elimination of ractopamine residues in beef cattle plasma and urine

Obj ective]Eliminating rule of ractopamine residue in plasma and urine of beef cattle was in-vestigated.Method]Three Chinese Simmental cross beef cattle were continuously fed ractopamine in a dose of 2.01 mg/(kg·d)weight/day for 28 days.Plasma and urine samples were collected on treated days of 1,7,14,21,28 and withdrawal days of 3,7,14,28 d,The ractopamine concentrations were determined by high performance liquid chromatography tandem mass spectrometry (HPLC-MS-MS)method.Result]The ractopamine concentrations in plasma and urine peaked on the 7 th treated day,and the residue in plas-ma and urine was (6.55±1.93)and (8 402.03±1 307.09)ng/mL,respectively.Ractopamine residues gradually decreased after the peak value and dropped rapidly after stopping treatment.After drug with-drawal for 3 days,the concentrations of parent ractopamine in plasma and urine were (0.60±0.01)and (1 334.93±25.74)ng/mL,respectively.Parent ractopamine residues was (5.77±0.10)ng/mL in urine and not detected in plasma after withdrawal for 28 days.After the hydrolysis of conjugates,ractopamine content in urine was significantly higher than that before hydrolysis (P<0.05).Conclusion]Urine is a more favorable target for supervision before slaughter compared to plasma.