The immune response varies between pigs, as not all pigs have the same response to a stressor. This variation may exist between individuals due to body weight (BW) or body composition, which may impact the capacity for coping with an immune challenge (IC). Tryptophan (Trp), threonine (Thr), and methionine (Met) requirements might also play a considerable part in supporting immune system activation while reducing variation between pigs; however, the latter has yet to be reported. This exploratory study investigated the effect of initial BW (light vs. heavy-weight) and supplementation of Trp, Thr, and Met above National Research Council (NRC) requirements on feeding behavior and the coping capacity of growing pigs under an IC. Eighty gilts were categorized into 2 groups according to BW: light-weight (LW, 22.5 kg) and heavy-weight pigs (HW, 28.5 kg). Both BW groups were group-housed for a 28-d trial in a good or poor sanitary condition (SC). Pigs within a poor SC were orally inoculated with 2 × 109 colony units of Salmonella Typhimurium, and fresh manure from a pig farm was spread on the floor. Pigs within good SC were not inoculated, nor was manure spread. Two diets were provided within each SC: control (CN) or supplemented (AA+) with Trp, Thr, and Met at 120% of NRC recommended levels. A principal component analysis was performed in R, and a feeding behavior index was calculated in SAS. Results showed that LW and HW pigs were clustered separately on day 0, where LW pigs had a positive correlation with body lipid percentage (r = 0.83), and HW pigs had a positive correlation with body protein percentage (r = 0.75). After the IC, the cluster configuration changed, with diets influencing LW more than HW pigs within poor SC. On day 14, LW fed AA + diet in poor SC was clustered separately from LW pigs fed CN diet, whereas LW fed AA + and CN diets in good SC were clustered together. For feeding behavior, in both analyzed periods (period 1: days 7 to 14; period 2: days 21 to 28), LW had lower total feed intake and shorter meals than HW pigs (P < 0.10), independent of the SC. Furthermore, LW pigs fed AA + diet had a more regular feed intake pattern than those fed CN diet, while a more irregular pattern was observed for HW pigs fed AA + diet than CN diet at period 2. These findings suggest that supplementing Trp, Thr, and Met above requirements may be a nutritional strategy for LW pigs under IC by improving feed intake regularity and reducing the probability of being susceptible to IC.

中文翻译：

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体型很重要：与体重较重的猪相比，低体重猪对免疫攻击和氨基酸补充的反应高于估计需求


免疫反应因猪而异，因为并非所有猪对应激源的反应都相同。由于体重 （BW） 或身体成分，个体之间可能存在这种差异，这可能会影响应对免疫挑战 （IC） 的能力。色氨酸 （Trp）、苏氨酸 （Thr） 和蛋氨酸 （Met） 需求也可能在支持免疫系统激活方面发挥重要作用，同时减少猪之间的差异;然而，后者尚未被报道。这项探索性研究调查了初始 BW （轻与重） 和补充 Trp 、 Thr 和 Met 高于国家研究委员会 （NRC） 要求对 IC 下生长猪的摄食行为和应对能力的影响。根据 BW 将 80 头后备母猪分为 2 组：轻量（LW，22.5 kg）和重体重猪（HW，28.5 kg）。两个 BW 组均在卫生条件良好或较差 （SC） 下进行 28 d 试验。在较差的 SC 中，用 2 × 109 个菌落单位的鼠伤寒沙门氏菌口服接种，并将来自养猪场的新鲜粪便撒在地板上。良好 SC 内的猪没有接种，粪便也没有撒播。每个 SC 提供两种饮食：对照 （CN） 或补充 （AA+） Trp、Thr 和 Met，含量为 NRC 推荐水平的 120%。在 R 中进行主成分分析，在 SAS 中计算摄食行为指数。结果显示，LW 和 HW 猪在 0 d 分别聚集，其中 LW 猪与体脂百分比呈正相关 （r = 0.83），HW 猪与体蛋白百分比呈正相关 （r = 0.75）。IC 后，集群配置发生了变化，在较差的 SC 中，日粮对 LW 的影响大于 HW 猪。 第 14 天，在较差的 SC 中饲喂 AA + 日粮的 LW 与饲喂 CN 日粮的 LW 猪分开聚集，而在良好 SC 中饲喂 AA + 的 LW 和 CN 日粮被聚集在一起。对于摄食行为，在两个分析期 （期 1： 第 7 至 14 天;期 2： 第 21 至 28 天） 中，LW 的总采食量低于 HW 猪，膳食时间短 （P < 0.10），与 SC 无关。此外，饲喂 AA + 日粮的 LW 猪比饲喂 CN 日粮的猪具有更规律的采食模式，而在第 2 期时，饲喂 AA + 日粮的 HW 猪比 CN 日粮的 HW 猪观察到更不规则的模式。这些发现表明，补充 Trp 、 Thr 和 Met 上述要求可能是 IC 下 LW 猪的一种营养策略，可以提高采食规律性并降低易感 IC 的可能性。