Most amino acid requirement trials appear for whole-body responses, but there is little information concerning amino acid incorporation in individual tissues, which may vary according to the age. L-[¹⁵N] threonine was used to evaluate its incorporation rate and distribution among broiler tissues in different ages. Seventy-two male broiler chickens were distributed into three different phases: starter (4 to 9 days old), grower (18 to 23 days old) and finisher phase (32 to 37 days old). L-[¹⁵N] threonine was added on balanced diets, and birds were fed for five days in each phase. Enriched samples of breast muscle, feathers, liver, jejunum and plasma were collected at 0, 6, 12, 24, 48, 72, 96 and 120 hr after fed birds with the tracer in each phase. In the tissues were analysed dry matter, nitrogen and stable nitrogen. The ¹⁵N isotope abundance according to the time was fitted into exponential or linear equations using a same intercept. The ratio of the steepness or slope coefficients was determined to compare the L-[¹⁵N] threonine incorporation according to the age. In addition, L-[¹⁵N] threonine mass balances were performed to assess the L-[¹⁵N] threonine distribution among the evaluated tissues. Except for feathers, the L-[¹⁵N] threonine incorporation rate decreased with ageing. Taking into account the L-[¹⁵N] threonine distribution in the tissues, only in the jejunum was not observed an increase as the broiler grew. The L-[¹⁵N] incorporation varied in each tissue and according to the age of the broiler chickens. These outcomes could be useful to comprehend changes in amino acid requirements tissue-specific according to age.

中文翻译：

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使用 L-[15N] 苏氨酸将苏氨酸掺入生长肉鸡的组织中

大多数氨基酸需求试验出现在全身反应中，但很少有关于氨基酸在个体组织中掺入的信息，这些信息可能因年龄而异。L-[ ¹⁵ N] 苏氨酸用于评估其在不同年龄肉鸡组织中的掺入率和分布。72 只雄性肉鸡被分配到三个不同的阶段：开始阶段（4 到 9 天大）、成长阶段（18 到 23 天大）和育肥阶段（32 到 37 天大）。L-[ ¹⁵N] 苏氨酸在均衡饮食中添加，每个阶段喂鸟五天。在每个阶段用示踪剂喂养鸟类后 0、6、12、24、48、72、96 和 120 小时，收集了丰富的胸肌、羽毛、肝脏、空肠和血浆样本。在组织中分析干物质、氮和稳定氮。使用相同截距将根据时间的¹⁵ N 同位素丰度拟合成指数或线性方程。确定陡度或斜率系数的比率以根据年龄比较L-[ ¹⁵ N] 苏氨酸掺入。此外，还进行了 L-[ ¹⁵ N] 苏氨酸质量平衡以评估 L-[ ¹⁵N] 苏氨酸在评估组织中的分布。除了羽毛，L-[ ¹⁵ N] 苏氨酸的掺入率随着年龄的增长而下降。考虑到 L-[ ¹⁵ N] 苏氨酸在组织中的分布，仅在空肠中未观察到随着肉鸡生长而增加。L-[ ¹⁵ N] 掺入在每个组织中不同，并且根据肉鸡的年龄而变化。这些结果可能有助于理解不同年龄组织特异性氨基酸需求的变化。