Low crude protein (CP) formulations with supplemental amino acids (AA) are used to enhance intestinal health, reduce costs, minimize environmental impact, and maintain growth performance of pigs. However, extensive reduction of dietary CP can compromise growth performance due to limited synthesis of non-essential AA and limited availability of bioactive compounds from protein supplements even when AA requirements are met. Moreover, implementing a low CP formulation can increase the net energy (NE) content in feeds causing excessive fat deposition. Additional supplementation of functional AA, coupled with low CP formulation could further enhance intestinal health and glucose metabolism, improving nitrogen utilization, and growth performance. Three experiments were conducted to evaluate the effects of low CP formulations with supplemental AA on the intestinal health and growth performance of growing-finishing pigs. In Exp. 1, 90 pigs (19.7 ± 1.1 kg, 45 barrows and 45 gilts) were assigned to 3 treatments: CON (18.0% CP, supplementing Lys, Met, and Thr), LCP (16.0% CP, supplementing Lys, Met, Thr, Trp, and Val), and LCPT (16.1% CP, LCP + 0.05% SID Trp). In Exp. 2, 72 pigs (34.2 ± 4.2 kg BW) were assigned to 3 treatments: CON (17.7% CP, meeting the requirements of Lys, Met, Thr, and Trp); LCP (15.0% CP, meeting Lys, Thr, Trp, Met, Val, Ile, and Phe); and VLCP (12.8% CP, meeting Lys, Thr, Trp, Met, Val, Ile, Phe, His, and Leu). In Exp. 3, 72 pigs (54.1 ± 5.9 kg BW) were assigned to 3 treatments and fed experimental diets for 3 phases (grower 2, finishing 1, and finishing 2). Treatments were CON (18.0%, 13.8%, 12.7% CP for 3 phases; meeting Lys, Met, Thr, and Trp); LCP (13.5%, 11.4%, 10.4% CP for 3 phases; meeting Lys, Thr, Trp, Met, Val, Ile, and Phe); and LCPG (14.1%, 12.8%, 11.1% CP for 3 phases; LCP + Glu to match SID Glu with CON). All diets had 2.6 Mcal/kg NE. In Exp. 1, overall, the growth performance did not differ among treatments. The LCPT increased (P < 0.05) Claudin-1 expression in the duodenum and jejunum. The LCP and LCPT increased (P < 0.05) CAT-1, 4F2hc, and B0AT expressions in the jejunum. In Exp. 2, overall, the VLCP reduced (P < 0.05) G:F and BUN. The LCP and VLCP increased (P < 0.05) the backfat thickness (BFT). In Exp. 3, overall, growth performance and BFT did not differ among treatments. The LCPG reduced (P < 0.05) BUN, whereas increased the insulin in plasma. The LCP and LCPG reduced (P < 0.05) the abundance of Streptococcaceae, whereas the LCP reduced (P < 0.05) Erysipelotrichaceae, and the alpha diversity. When implementing low CP formulation, CP can be reduced by supplementation of Lys, Thr, Met, Trp, Val, and Ile without affecting the growth performance of growing-finishing pigs when NE is adjusted to avoid increased fat deposition. Supplementation of Trp above the requirement or supplementation of Glu in low CP formulation seems to benefit intestinal health as well as improved nitrogen utilization and glucose metabolism.

中文翻译：

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含有补充氨基酸的低粗蛋白配方，对生长肥育猪的肠道健康和生长性能有影响

含有补充氨基酸 (AA) 的低粗蛋白 (CP) 配方用于增强肠道健康、降低成本、最大限度地减少环境影响并保持猪的生长性能。然而，由于非必需 AA 的合成有限，并且即使满足 AA 需求，蛋白质补充剂中生物活性化合物的可用性也有限，大幅减少日粮 CP 可能会损害生长性能。此外，采用低CP配方会增加饲料中的净能（NE）含量，导致过多的脂肪沉积。额外补充功能性 AA，再加上低 CP 配方，可以进一步增强肠道健康和葡萄糖代谢，提高氮利用率和生长性能。进行了三项实验来评估添加 AA 的低 CP 配方对生长肥育猪肠道健康和生长性能的影响。在Exp。如图 1 所示，90 头猪（19.7 ± 1.1 kg，45 头公猪和 45 头后备母猪）被分配到 3 个处理组：CON（18.0% CP，补充 Lys、Met 和 Thr）、LCP（16.0% CP，补充 Lys、Met、Thr） Trp 和 Val）和 LCPT（16.1% CP、LCP + 0.05% SID Trp）。在Exp。 2、72头猪（34.2±4.2kg体重）被分配到3个处理：CON（17.7％CP，满足Lys、Met、Thr和Trp的要求）； LCP（15.0% CP，满足 Lys、Thr、Trp、Met、Val、Ile 和 Phe）；和 VLCP（12.8% CP，满足 Lys、Thr、Trp、Met、Val、Ile、Phe、His 和 Leu）。在Exp。如图 3 所示，72 头猪（54.1 ± 5.9 kg 体重）被分配到 3 个处理组，并饲喂 3 个阶段的实验日粮（生长期 2、育肥期 1 和育肥期 2）。治疗为 CON（3 个阶段分别为 18.0%、13.8%、12.7% CP；满足 Lys、Met、Thr 和 Trp）； LCP（3 个阶段 13.5%、11.4%、10.4% CP；满足 Lys、Thr、Trp、Met、Val、Ile 和 Phe）；和 LCPG（3 相 14.1%、12.8%、11.1% CP；LCP + Glu，以将 SID Glu 与 CON 匹配）。所有饮食均含有 2.6 麦卡/千克 NE。在Exp。 1、总体而言，各处理间的生长表现没有差异。 LCPT 增加 (P < 0.05) 十二指肠和空肠中 Claudin-1 的表达。 LCP 和 LCPT 增加 (P < 0.05) 空肠中 CAT-1、4F2hc 和 B0AT 的表达。在Exp。如图 2 所示，总体而言，VLCP 降低了 (P < 0.05) G:F 和 BUN。 LCP 和 VLCP 增加了（P < 0.05）背膘厚度（BFT）。在Exp。如图3所示，总体而言，处理之间的生长性能和BFT没有差异。 LCPG 降低了 (P < 0.05) BUN，而增加了血浆中的胰岛素。 LCP和LCPG降低了链球菌科的丰度（P < 0.05），而LCP降低了丹毒菌科的丰度（P < 0.05）和α多样性。实施低CP配方时，通过补充Lys、Thr、Met、Trp、Val和Ile来降低CP，同时调整NE以避免脂肪沉积增加，而不影响生长肥育猪的生长性能。在低 CP 配方中补充超过需要量的色氨酸或补充谷氨酸似乎有利于肠道健康以及改善氮利用率和葡萄糖代谢。