Carew L B, Evarts K G, Alster F A
Department of Animal and Food Sciences, University of Vermont, Burlington 05405, USA.
Poult Sci. 1998 Feb;77(2):295-8. doi: 10.1093/ps/77.2.295.
The consequences of dietary excesses of 10 essential amino acids, His, Ile, Phe, Trp, Val, Arg, Leu, Lys, Met, Thr, on growth, feed intake and plasma levels of triiodothyronine (T3) and thyroxine (T4) in growing chicks were investigated. Each amino acid was added to a starter ration to bring it to a level 2.84x above the National Research Council (1984) requirement. Excesses of all amino acids except His and Leu caused significant reductions in weight gain. Of the amino acid excesses that reduced growth, only Trp and Val did not also reduce feed intake. Gain:feed decreased significantly only in chicks consuming excess Arg, Lys, Phe, and Trp. Chicks fed excesses of Ile and Val had plasma T3 levels that were statistically higher than control levels; none of the other amino acid excesses significantly altered blood concentrations of this hormone. Compared to the control, plasma T4 levels were not significantly altered by the amino acid excesses, but there was a significant difference between Trp and Val, the latter being lower. This study shows that high dietary levels of essential amino acids cause depressions in weight gain and feed intake, and, with Ile and Val, these depressions are accompanied by elevations in plasma T3 levels. Otherwise, the amino acid excesses had little effect on plasma levels of thyroid hormones.
研究了日粮中10种必需氨基酸（组氨酸、异亮氨酸、苯丙氨酸、色氨酸、缬氨酸、精氨酸、亮氨酸、赖氨酸、蛋氨酸、苏氨酸）过量对生长雏鸡生长、采食量以及血浆三碘甲状腺原氨酸（T3）和甲状腺素（T4）水平的影响。将每种氨基酸添加到雏鸡开食日粮中，使其达到高于美国国家研究委员会（1984年）需求量2.84倍的水平。除组氨酸和亮氨酸外，所有氨基酸过量均导致体重增加显著降低。在导致生长降低的氨基酸过量中，只有色氨酸和缬氨酸没有使采食量降低。仅在摄入过量精氨酸、赖氨酸、苯丙氨酸和色氨酸的雏鸡中，料重比显著降低。饲喂过量异亮氨酸和缬氨酸的雏鸡血浆T3水平在统计学上高于对照水平；其他氨基酸过量均未显著改变该激素的血液浓度。与对照相比，氨基酸过量并未显著改变血浆T4水平，但色氨酸和缬氨酸之间存在显著差异，缬氨酸水平较低。本研究表明，日粮中高水平的必需氨基酸会导致体重增加和采食量下降，而异亮氨酸和缬氨酸过量时，这些下降伴随着血浆T3水平升高。否则，氨基酸过量对甲状腺激素的血浆水平影响很小。
