Scheele C W, Decuypere E, Vereijken P F, Schreurs F J
Spelderholt Centre for Poultry Research and Information Services, Beekbergen, The Netherlands.
Poult Sci. 1992 Dec;71(12):1971-84. doi: 10.3382/ps.0711971.
Effects of different broiler stocks, ambient temperatures (Ta), dietary energy content (AME), and dietary levels of unsaturated fat on plasma thyroid and growth hormone concentrations and energy metabolism were studied. An experiment with a 2 x 2 x 2 x 2 factorial split-plot arrangement of treatments with 96 groups of 12 male broilers each was performed. Blood samples were taken at 3, 4, and 5 wk of age. Energy metabolism parameters were determined over an entire period from 1 to 5 wk of age. Chickens from a line selected for fast growth rate and low feed conversion ratio but also more sensitive to heart failure syndrome (HFS) and ascites (Line SS) than commercial birds (Line BC) exhibited the greatest responses to experimental factors. Differences in levels of plasma thyroxine (T4), triiodothyronine (T3), reverse triiodothyronine (rT3), and growth hormone (GH) between stocks at different ages were highly dependent on Ta and dietary fat content. Differences in heat production per metabolic weight, percentage of retained fat energy in retained energy, and efficiency of AME intake for retained energy between stocks corresponded to differences in hormone levels. High-fat diets (polyunsaturated fatty acids) inhibited the extra thyroidal conversion of T4 to T3 in both stocks. Differences between stocks in T3 and rT3 levels in plasma indicated that BC birds (in contrast to SS birds) were better able to compensate for an inhibited T4 conversion to T3 by producing more T4. Overall results suggest that the occurrence of HFS and ascites in SS birds could be initiated independently by different factors. These factors might be a limited thyroid hormone production and a lower capacity for oxygen consumption. An inverse relationship between T3 and GH levels found in particular combinations of experimental factors, together with changes in fat deposition, support published concepts about the positive effects of T3 on lipogenesis and GH on lipolysis.
研究了不同肉鸡品种、环境温度（Ta）、日粮能量含量（AME）和日粮不饱和脂肪水平对血浆甲状腺激素和生长激素浓度以及能量代谢的影响。采用2×2×2×2析因裂区试验设计，共96组，每组12只雄性肉鸡。在3、4和5周龄时采集血样。在1至5周龄的整个期间测定能量代谢参数。与商品鸡（BC系）相比，一个为快速生长率和低饲料转化率而选育，但对心力衰竭综合征（HFS）和腹水更敏感的品系（SS系）的鸡对实验因素表现出最大反应。不同年龄品系间血浆甲状腺素（T4）、三碘甲状腺原氨酸（T3）、反三碘甲状腺原氨酸（rT3）和生长激素（GH）水平的差异高度依赖于Ta和日粮脂肪含量。不同品系间每代谢体重产热、保留能量中保留脂肪能量的百分比以及AME摄入量用于保留能量的效率差异与激素水平差异相对应。高脂日粮（多不饱和脂肪酸）在两个品系中均抑制了T4向T3的外周转化。品系间血浆T3和rT3水平的差异表明，BC系鸡（与SS系鸡不同）能够通过产生更多T4更好地补偿T4向T3转化的抑制。总体结果表明，SS系鸡中HFS和腹水的发生可能由不同因素独立引发。这些因素可能是甲状腺激素分泌受限和耗氧能力较低。在特定实验因素组合中发现的T3和GH水平之间的负相关关系，以及脂肪沉积的变化，支持了已发表的关于T3对脂肪生成和GH对脂肪分解的积极作用的概念。
