Carew L B, Alster F A, Foss D C, Scanes C G
J Nutr. 1983 Sep;113(9):1756-65. doi: 10.1093/jn/113.9.1756.
Broiler chicks from 2 to 4 weeks of age were fed control (0.23%) and deficient (0.115, 0.058%) levels of L-tryptophan. Separate groups of control chicks were pair-fed daily with the deficient chicks. Deficient chicks grew less efficiently than did pair-fed controls. Plasma triiodothyronine (T3) was elevated in deficient chicks, especially compared to pair-fed controls, and this was accompanied by lower reverse T3. Plasma thyroxine (T4) was also reduced with 0.059% tryptophan. However, thyroid weights and follicle diameters were unchanged. Reductions in weight gain and bone growth, increases in pituitary and pineal weights, and elevations in plasma GH occurred in the tryptophan-deficient chicks apart from any effect due to reductions in feed intake. Comb and testis size, and plasma testosterone were little affected by the deficiency. Based on changes in plasma T3 levels and feed conversion efficiencies, we conclude that tryptophan-deficient chicks show signs of relative hyperthyroidism and energy wastage compared to pair-fed controls. The elevations in plasma growth hormone and T3 support the concept that serotonin is a negative modulator of the synthesis or release of these hormones in chickens.
对2至4周龄的肉鸡雏鸡饲喂对照水平（0.23%）和缺乏水平（0.115%、0.058%）的L-色氨酸。将单独的对照雏鸡组每天与缺乏组雏鸡进行配对饲喂。与配对饲喂的对照雏鸡相比，缺乏组雏鸡的生长效率较低。缺乏组雏鸡的血浆三碘甲状腺原氨酸（T3）升高，尤其是与配对饲喂的对照雏鸡相比，同时反式T3降低。血浆甲状腺素（T4）在色氨酸含量为0.059%时也降低。然而，甲状腺重量和卵泡直径没有变化。除了采食量减少的影响外，色氨酸缺乏的雏鸡体重增加和骨骼生长减少，垂体和松果体重量增加，血浆生长激素升高。鸡冠和睾丸大小以及血浆睾酮受缺乏的影响较小。基于血浆T3水平和饲料转化效率的变化，我们得出结论，与配对饲喂的对照雏鸡相比，色氨酸缺乏的雏鸡表现出相对甲状腺功能亢进和能量浪费的迹象。血浆生长激素和T3的升高支持了血清素是鸡体内这些激素合成或释放的负调节剂这一概念。
