Thyroid hormones are powerful regulators of growth, development and basal metabolic rate and can be dysregulated under conditions of severe stress or illness. To understand the role of these hormones in porcine disease response, serum samples were obtained from 3 batches of nursery-aged pigs (n=208) exposed to a natural polymicrobial disease challenge with an array of bacterial and viral pathogens. Levels of total thyroxin (T4) and triiodothyronine (T3) assessed in sera by radioimmunoassay (RIA), decreased significantly by 14 days post exposure (DPE). Levels of T3 partially rebounded by 48 DPE, while T4 levels remain depressed. Post-exposure T3 and T4 levels were positively correlated with acute and long-term average daily gain. Cross-sectional sampling of animals maintained at the high health source farms, showed no equivalent change in either hormone when managed under standard industry conditions. To further elucidate the effect of PRRSV-infection on thyroid hormone levels, archived sera over 42 days post inoculation (DPI) from nursery pigs (N=190) challenged with one of two PRRSV2 strains by the PRRS Host Genetics Consortium (PHGC) were similarly assessed, with animals selected in a two-by-two design, to investigate biological extremes in average daily gain (ADG) and viral load. All animals showed a similar decrease in both thyroid hormones reaching a minimum at 7 DPI and returning to near pre challenge levels by 42 DPI. Post challenge T3 and T4 levels were significantly greater in high ADG groups, with no significant association with viral load or strain. The results of this study demonstrate porcine susceptibility to thyroid disruption in response to disease challenge and demonstrate a relationship between this response and growth performance.

中文翻译：

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多微生物或猪繁殖与呼吸综合征病毒 2 攻击后饲养猪的甲状腺激素抑制

甲状腺激素是生长、发育和基础代谢率的强大调节剂，在严重压力或疾病的情况下可能会失调。为了了解这些激素在猪疾病反应中的作用，从 3 批暴露于具有一系列细菌和病毒病原体的天然多微生物疾病挑战的保育龄猪 (n = 208) 中获取血清样本。通过放射免疫测定法 (RIA) 在血清中评估的总甲状腺素 (T4) 和三碘甲状腺原氨酸 (T3) 水平在暴露后 14 天 (DPE) 显着下降。T3 水平部分反弹 48 DPE，而 T4 水平仍然低迷。暴露后 T3 和 T4 水平与急性和长期平均日增重呈正相关。在高健康源农场饲养的动物的横断面抽样，在标准工业条件下进行管理时，两种激素均未显示出等效变化。为了进一步阐明 PRRSV 感染对甲状腺激素水平的影响，接种后 42 天 (DPI) 的保育猪 (N=190) 用 PRRS 宿主遗传学联盟 (PHGC) 的两种 PRRSV2 毒株中的一种进行攻击的存档血清相似。评估，以二乘二的设计选择动物，以研究平均日增重 (ADG) 和病毒载量的生物学极端情况。所有动物都表现出相似的甲状腺激素降低，在 7 DPI 时达到最小值，并在 42 DPI 时恢复到接近攻击前的水平。攻击后 T3 和 T4 水平在高 ADG 组中显着更高，与病毒载量或病毒株没有显着关联。