The current study was conducted to optimize parameters of the 15 N-leucine single-administration method for measuring endogenous amino acid losses in chicken. Experiment 1 was designed to provide suitable parameters of gas chromatography-mass spectrometry ( GC-MS ) for determing 15 N-enrichment of leucine (APEL) and ascertain an appropriate scope of APEL in samples. Experiment 2 was carried out to optimize ad-ministration parameters of 15 N-leucine, using 48 Avian roosters to study the effects of administration methods (intramuscular injection and intravenous injection) and doses (10, 20 and 30 mg/kg BW) of 15N-leucine on 15 N-enrichment in main secretory sources of endogenous amino acids. The results showed as follows: 1 ) the biggest characteristic fragment ion peaks of MTBSTFA derivatives of leucine in GC-MS is m/z=200. Precision and accuracy of measurement were poor when APEL<0.1% in samples; measurement precision and accuracy respectively ranged from 4.3% to 9.7% and -5.9% to 4.1% when APEL ranged from 0.1% to 3.2%, and the standard curve of mixtures of natural and 15N-leucine showed a good linear relationship (R2=0.989). 2) The values of APEL in main secretory sources of endogenous amino acids were greater than 0.1% for 15N-leucine administration doses of 20 and 30 mg/kg BW. The experimental birds administrated 15N-leucine through intra-venous injection showed harmful stress including congestion and extravasation at the injection sites. 3 ) There were not administration methods and doses interaction effects ( P>0.05) of APEL in main secretory sources of endogenous amino acids. The values of APEL in main secretory sources of endogenous amino acids were in-creased significantly (P<0.05) with an increase of administration dose. The values of APEL among different secretory sources had no significant difference (P>0.05) at 15N-leucine administration doses of 20 mg/kg BW. However, the values of APEL in pancreas and intestinal mucosa were influenced significantly (P<0.05) by 15 N-leucine administration method. In conclusion, the 15 N-leucine administration doses of 20 mg/kg BW is se-lected to meet the requirements of GC-MS analysis, and intramuscular injection of 15 N-leucine is applied to re-duce harmful stress, simplify the operating procedure and reduce the cost.%本研究旨在优化一次注射15 N-亮氨酸(15 N-Leu)示踪法检测鸡内源氨基酸( AA)损失量的适宜参数。试验一,研究气相色谱-质谱联用仪(GC-MS)测定Leu的15N丰度(APEL)的适宜参数,确定适宜的丰度测定范围；试验二,以48只艾维茵公鸡为对象,研究15 N-Leu的引入方式(肌肉注射和静脉注射)和剂量(10、20和30 mg/kg BW)对内源AA主要分泌源中APEL 的影响,旨在优化15 N-Leu的引入参数。结果显示：1) Leu的MTBSTFA衍生物在GC-MS上的最大特征碎片离子峰为质荷比(m/z)=200；当样品APEL<0.1%时,测定精准度(13.1%)和准确度(13.8%)较差；当样品 APEL 为0.1%~3.2%时,测定精准度和准确度分别为4.3%~9.7%和-5.9%~4.1%,所得到的同位素稀释曲线良好, R2为0.989；2)当15 N-Leu 引入剂量为20和30 mg/kg BW时,内源AA主要分泌源中APEL>0.1%；静脉注射的试鸡在注射部位出现淤血、外渗现象；3)15N-Leu 引入方式和剂量对内源 AA 主要分泌源的 APEL 不存在交互作用(P>0.05)；各分泌源的APEL 均随引入剂量的增大而显著增加(P<0.05),当引入剂量为20 mg/kg BW时,各分泌源间的APEL 无显著差异( P>0.05)；引入方式显著影响胰腺和肠黏膜的 APEL (P<0.05)。以上结果表明,15N-Leu引入剂量为20 mg/kg BW可满足GC-MS分析要求,同时选取肌肉注射可减少动物应激、简化操作程序,并降低成本。
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