Department of Animal Sciences and Industry, Kansas State University, Manhattan, KS 66506-0201, USA.
J Anim Sci Biotechnol. 2014 Feb 18;5(1):12. doi: 10.1186/2049-1891-5-12.
Immune system activation begins a host of physiological responses. Infectious agents are recognized by monocytes and macrophages which in turn stimulate cytokine production. It is the hormone-like factors called cytokines that orchestrate the immune response. The classic responses observed with immune system activation and cytokine production include: anorexia, fever, lethargy, recruitment of other immune cells, and phagocytosis. While production of immune system components is known to require some amino acids, increases in amino acid requirements are more than offset by the associated decrease in protein accretion and increased muscle protein degradation that also accompanies immune system activation. However, the biggest impact of cytokine production is a decrease in feed intake. Therefore, as feed intake decreases, the energy needed to drive protein synthesis is also decreased. This suggests that diets should still be formulated on a similar calorie:lysine ratio as those formulated for non-immune challenged pigs. The evidence is sparse or equivocal for increasing nutrient requirements during an immune challenge. Nutritionists and swine producers should resist the pressure to alter the diet, limit feed, or add expensive feed additives during an immune challenge. While immune stimulation does not necessitate changes in diet formulation, when pigs are challenged with non-pathogenic diarrhea there are potential advantages on gut health with the increased use of crystalline amino acids rather than intact protein sources (i.e., soybean meal). This is because reducing crude protein decreases the quantity of fermentable protein entering the large intestine, which lowers post weaning diarrhea. It also lowers the requirement for expensive specialty protein sources or other protein sources such as soybean meal that present immunological challenges to the gut. The objective of this review is two-fold. The first is to discuss immunity by nutrition interactions, or lack thereof, and secondly, to review amino acid requirement estimates for nursery pigs.
免疫系统激活会引发一系列生理反应。单核细胞和巨噬细胞识别病原体，然后刺激细胞因子的产生。正是这些被称为细胞因子的激素样因子协调了免疫反应。经典的免疫反应和细胞因子的产生包括：厌食、发热、嗜睡、其他免疫细胞的募集和吞噬作用。虽然免疫系统成分的产生需要一些氨基酸，但氨基酸需求的增加远远超过了蛋白质积累减少和随之而来的肌肉蛋白质降解的增加，这些变化也伴随着免疫系统的激活。然而，细胞因子产生的最大影响是饲料摄入量的减少。因此，随着采食量的减少，驱动蛋白质合成所需的能量也会减少。这表明，在制定用于非免疫挑战猪的日粮时，仍应按照相似的卡路里：赖氨酸比例来制定日粮。在免疫挑战期间，增加营养需求的证据很少或不确定。营养师和养猪生产者应抵制在免疫挑战期间改变日粮、限制饲料或添加昂贵的饲料添加剂的压力。虽然免疫刺激不一定需要改变日粮配方，但当猪受到非致病性腹泻的挑战时，与使用完整蛋白质来源（如豆粕）相比，增加使用结晶氨基酸可能对肠道健康有潜在优势。这是因为降低粗蛋白减少了进入大肠的可发酵蛋白的数量，从而降低了断奶后腹泻的发生率。它还降低了对昂贵的特种蛋白质来源或其他蛋白质来源（如豆粕）的需求，因为这些蛋白质来源对肠道具有免疫挑战。本综述的目的有两个。首先是讨论营养与免疫的相互作用，或者缺乏这种相互作用，其次是回顾仔猪氨基酸需求估计值。
