Department of Animal and Poultry Science, University of Guelph, Guelph, ON N1G 2W1, Canada.
J Anim Sci. 2012 Oct;90(10):3485-91. doi: 10.2527/jas.2011-4830. Epub 2012 Jul 31.
The effect of immune system stimulation (ISS) on N retention and Trp utilization in pigs fed Trp-limiting diets was evaluated using 36 growing pigs (20.0 ± 1.1 kg BW; 3 blocks of 12 barrows). Pigs were randomly assigned to 1 of 5 diets (Diet 1, 2, 4, and 5, n = 7; Diet 3, n = 8) and fed restrictively at 800 g/d. Diets 1 to 4 were generated by blending Diet 1 with a protein-free supplement and were calculated to contain varying amounts of standardized ileal digestible (SID) Trp (1.31, 1.05, 0.80, and 0.55 g/kg). To confirm that Trp was the first-limiting AA in Diets 1 to 4, an additional diet was used (Diet 5), which was equivalent to Diet 4 and contained 0.34 g/kg of added Trp. After a 5-d adaptation period, pigs were injected every 2 d with increasing amounts of E. coli lipopolysaccharide to induce ISS (initial dose 20 μg/kg BW, increasing 15% each subsequent injection). Whole body N balance was measured in 3 periods: before immune stimulation (pre-ISS) and during ISS in 2 subsequent periods (ISS-1, 3 d; ISS-2, 4 d). Regression analysis was used to estimate the marginal efficiency of Trp utilization for whole body protein deposition (PD; N retention × 6.25). Plasma concentrations of acute-phase proteins and white blood cell counts increased (P < 0.001) and plasma albumin decreased (P < 0.001) during ISS. Nitrogen retention increased (P < 0.001) as Trp intake increased. Nitrogen retention was numerically greater but not statistically different between Diet 5 (added Trp diet) and Diet 4. Whole body N retention was less (P < 0.05) during ISS due primarily to an increase (P < 0.05) in urinary N excretion. There was a linear response (P < 0.05) in N retention, urinary N, and total excreted N to increasing Trp intake. Protein deposition increased by 88.2 ± 5.2, 82.5 ± 5.1, and 92.5 ± 3.4 g/d for each additional g/d of SID Trp intake during pre-ISS, ISS-1, and ISS-2, respectively, but the intercept was not different (-32.3 g/d). The slope of the response of PD to increasing Trp intake (based on the common intercept) was less during ISS-1 compared with pre-ISS (P = 0.01) or ISS-2 (P = 0.002) but not different between pre-ISS and ISS-2. Immune system stimulation reduced N retention in pigs fed limiting dietary Trp. The efficiency of Trp utilization for protein deposition was also reduced during ISS, indicating that the Trp requirement for PD is increased ∼7% during an inflammatory state.
免疫系统刺激（ISS）对限制色氨酸（Trp）摄入的猪的氮（N）保留和色氨酸利用的影响，通过 36 头生长猪（20.0±1.1kg 体重；3 个栏，每个栏 12 头阉公猪）进行评估。猪随机分配到 5 种日粮中的 1 种（日粮 1、2、4 和 5，n=7；日粮 3，n=8），并以 800g/d 的量进行限制饲养。日粮 1 至 4 通过与无蛋白补充料混合生成，并计算出含有不同量的标准化回肠可消化（SID）色氨酸（1.31、1.05、0.80 和 0.55g/kg）。为了确认 Trp 是日粮 1 至 4 中的第一限制氨基酸，还使用了另外一种日粮（日粮 5），该日粮与日粮 4 相同，但含有 0.34g/kg 的添加 Trp。适应期 5d 后，每隔 2d 给猪注射递增剂量的大肠杆菌脂多糖以诱导 ISS（初始剂量为 20μg/kgBW，随后每次注射增加 15%）。在 3 个时期测量全身 N 平衡：免疫刺激前（pre-ISS）和 ISS 后的 2 个时期（ISS-1，3d；ISS-2，4d）。使用回归分析估计色氨酸利用的边际效率用于全身蛋白质沉积（N 保留×6.25）。在 ISS 期间，急性相蛋白的血浆浓度和白细胞计数增加（P＜0.001），白蛋白浓度降低（P＜0.001）。随着 Trp 摄入量的增加，N 保留量增加（P＜0.001）。日粮 5（添加 Trp 日粮）和日粮 4 之间的 N 保留量没有统计学差异，但数值上更高。由于尿氮排泄增加（P＜0.05），ISS 期间全身 N 保留量减少。N 保留量、尿氮和总排泄氮对 Trp 摄入量的增加呈线性反应（P＜0.05）。在 pre-ISS、ISS-1 和 ISS-2 期间，每增加 1g/d 的 SID 色氨酸摄入，蛋白质沉积分别增加 88.2±5.2、82.5±5.1 和 92.5±3.4g/d，但截距没有差异（-32.3g/d）。在 ISS-1 时，PD 对 Trp 摄入量增加的反应斜率与 pre-ISS（P=0.01）或 ISS-2（P=0.002）相比降低，但 pre-ISS 和 ISS-2 之间没有差异。ISS 降低了限制 Trp 摄入的猪的 N 保留量。PD 中色氨酸利用的效率也在 ISS 期间降低，表明在炎症状态下，PD 的 Trp 需求增加了约 7%。
