Commercial diets are frequently formulated to meet or exceed nutrient levels including those of limiting essential amino acids (AA) covering potential individual variations within the herd. However, the provision of dietary excess of AA, such as Lys, may lead to reduced appetite and growth in pigs. The mechanisms modulating these responses have not been extensively investigated. This study evaluated the effect of Lys dietary excesses on performance and satiety biomarkers in post weaning pigs. Twenty-four pigs aged 21 d and weighing 6.81 ± 0.12 kg (mean ± SEM) were individually housed and offered 1 of 4 dietary treatments for 3 weeks: a diet containing a standardized ileal digestible Lys reaching 100% (T0), 120% (T1), 150% (T2) or 200% (T3) of the NRC (2012) requirements. At the end of the experiment, blood samples from the cephalic vein of the T0 and T3 groups were obtained for AA analysis. In addition, primary intestinal cultures from T0 pigs were used, following their humane killing, to evaluate the effect of Lys on gut hormone secretion and AA sensors gene expression under ex vivo conditions. Feed intake was linearly reduced (P < 0.001) and the weight gain to feed ratio reduced (P < 0.10) with increased dietary levels of Lys during the third- and first-week post weaning, respectively. Cholecystokinin concentration (P < 0.05) and the metabotropic glutamate receptor 1 and the solute carrier family 7 member 2 (P < 0.10) gene expression was enhanced in proximal jejunum tissues incubated with Lys at 20 mmol/L when compared to the control (Lys 0 mmol/L). Plasma Lys and Glu (P < 0.05) concentration increased in the T3 compared to T0 pigs. In contrast, plasma levels of His, Val, Thr, Leu (P < 0.05) and Gln (P < 0.10) were lower in T3 than T0 pigs. The present results confirm that excess dietary Lys inhibits hunger in pigs. Moreover, the results provide evidence of pre- and post-absorptive mechanisms modulating these responses. Lys dietary excesses should be narrowed, when possible, to avoid negative effects of the AA on appetite in pigs.

中文翻译：

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日粮中过量赖氨酸会降低猪的采食量、刺激空肠 CCK 分泌并改变必需和非必需血液 AA 谱

商业日粮的配制经常是为了达到或超过营养水平，包括限制必需氨基酸（AA）的营养水平，从而覆盖牛群内潜在的个体差异。然而，日粮中提供过量的氨基酸（例如赖氨酸）可能会导致猪的食欲和生长降低。调节这些反应的机制尚未得到广泛研究。本研究评估了赖氨酸饮食过量对断奶后仔猪生产性能和饱腹感生物标志物的影响。将 24 头 21 日龄、体重 6.81 ± 0.12 kg（平均值 ± SEM）的猪单独圈养，并提供 4 种日粮治疗中的一种，持续 3 周：含有标准化回肠可消化赖氨酸达到 100%（T0）、120%（T0）的日粮。 NRC (2012) 要求的 T1)、150% (T2) 或 200% (T3)。实验结束时，从T0组和T3组的头静脉采集血样进行AA分析。此外，在人道宰杀后，使用 T0 猪的原代肠道培养物来评估离体条件下赖氨酸对肠道激素分泌和 AA 传感器基因表达的影响。在断奶后第三周和第一周，随着赖氨酸日粮水平的增加，采食量线性减少（P < 0.001），增重与饲料的比率降低（P < 0.10）。与对照（Lys 0毫摩尔/升）。与 T0 猪相比，T3 猪的血浆 Lys 和 Glu 浓度增加（P < 0.05）。相反，T3猪的血浆His、Val、Thr、Leu（P < 0.05）和Gln（P < 0.10）水平低于T0猪。目前的结果证实，日粮中过量的赖氨酸会抑制猪的饥饿感。此外，结果提供了调节这些反应的吸收前和吸收后机制的证据。如果可能的话，应减少赖氨酸饮食过量，以避免 AA 对猪食欲的负面影响。