第177期：免疫系统激活提高生长猪蛋白质沉积对苏氨酸的需要量

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2019. J. Anim. Sci. 97(2):735-744

https://doi.org/10.1093/jas/sky468.

免疫系统激活提高生长猪蛋白质沉积对苏氨酸的需要量

Whitney D McGilvray, Hailey Wooten, Amanda R Rakhshandeh, Amy Petry, Anoosh Rakhshandeh

      前人的研究发现免疫系统激活会提高苏氨酸的利用率。但是，由于内源氨基酸可能会弥补日粮氨基酸的不足，所以苏氨酸利用率的提高并不意味着对日粮需要量的提高。本试验评估了免疫系统激活对苏氨酸不同需要量（如维持需要、苏氨酸沉积率）的影响。

      试验选用39头商品小母猪（初始重32±2.1kg），分别为单个代谢笼饲养，随机分为六个处理组。6个日粮中苏氨酸为第一限制性氨基酸。根据免疫应激组猪蛋白质沉积速度估算其氨基酸需要量，日粮苏氨酸含量分别为70%、90%、110%苏氨酸需要量。随着试验日粮适应期结束后，随机注射生理盐水或大肠杆菌脂多糖（25和35ug/kg体重），48小时后再注射一次。检测注射后72小时内机体氮平衡情况。监控猪机体温度变化情况，注射24小时后收集血液样品，检测血液化学指标。

    血液化学指标和体温结果表明猪只处于免疫应激状况（P＜0.03）。所有免疫应激组苏氨酸线性提高了蛋白沉积（P＜0.01）。从线性方程的斜率可以看出，蛋白沉积利用的标准可消化苏氨酸的边际利用效率不受免疫应激状态的影响。但是，从线性方程的截距来看，免疫应激大幅度的提高了SID苏氨酸的维持需要量（对照组VS应激组，-11.2 VS -56.3， SE13.2； P＜0.05）。

      总之，本试验结果说明免疫应激下生理状态的变化提高了苏氨酸的维持需要，进而导致对日粮苏氨酸需要要的提高。

Immune system stimulation increases dietary threonine requirements for protein deposition in growing pigs

Whitney D McGilvray, Hailey Wooten, Amanda R Rakhshandeh, Amy Petry, Anoosh Rakhshandeh

Previous studies have reported an increase in the utilization of threonine (Thr) during immune system stimulation(ISS). However, increased utilization of an AA during ISS may not reflect an increased dietary requirement, as endogenous sources may supply AA to meet the need for enhanced utilization. The current study evaluated the impact of ISS on components of dietary Thr requirements, i.e., maintenance requirement and the efficiency of Thr utilization. Thirty-nine gilts (initial BW 32 ± 2.1 kg) of commercially relevant genetics were individually housed in metabolism crates and fed one of six experimental diets in which Thr was the first limiting among other AA. Three levels of dietary Thr were tested within each ISS group: 70%, 90%, and 110% of daily Thr requirements, which were estimated based on the potential of each ISS group for protein deposition (PD). Following adaptation to the experimental diets, pigs from each dietary treatment group were injected with either increasing amounts of Escherichia coli lipopolysaccharide (ISS+; 25and 35 μg/kg BW) or saline (ISS&#8722;). Injections were given 48-h apart and whole-body nitrogen balance was measured for 72-h following the first injection. Body temperature (BT) was monitored and blood samples were collected 24 h after initiation of ISS and evaluated for measures of blood chemistry. Blood chemistry and BT results indicated an effective ISS in pigs (P < 0.03). Threonine intake increased PD in a linear fashion in both ISS groups (P < 0.01). The marginal efficiency of standardized ileal digestible (SID) Thr utilization for PD, represented by the slope, was not affected by ISS. However, ISS substantially increased the extrapolated maintenance SID Thr requirements, represented by the intercept at zero PD (ISS&#8722;vs. ISS+, &#8722;11.2vs. &#8722;56.3SE 13.2; P < 0.05). Collectively, our results indicated that the physiological changes associated with ISS increased the dietary SID Thr requirements for PD due to an increase in maintenance requirements.

原创： 上海亘泰