Mézes M, Surai P, Sályi G, Speake B K, Gaál T, Maldjian A
Department of Nutrition, Gödöllö University of Agricultural Sciences, Hungary.
Acta Vet Hung. 1997;45(3):349-60.
Deficiencies or disturbances of nutrition cause a variety of diseases and can arise in different ways. The amount of a particular nutrient in the diet may be insufficient to meet the requirements, the diet may contain substances that inactivate the nutrient or inhibit its absorption/utilisation, or metabolism may be upset by the interaction of dietary and environmental factors. Peroxidation of lipids or oxygen free radical generation in general is a physiological process important for cell metabolism, division and differentiation and also for the biosynthesis of hormones and prostaglandins. Free radicals generated through these processes are effectively scavenged by the antioxidant defence system. Uncontrolled lipid oxidation caused by disturbances of that system may play a crucial role in some important poultry diseases and toxicoses. The first route of lipid peroxide loading of the organism is via the feed, such as through oxidised lipids. Oxidised fatty acids are absorbed from the intestine mainly in the form of unsaturated keto compounds and initiate lipid peroxidation in the tissues. The second problem is the insufficient amount of antioxidants in the feed, e.g. vitamin E deficiency. Nutritional encephalomalacia is a problem in poultry production which depends both on the actual vitamin E supply and the dietary amount of polyunsaturated fatty acids. In young birds the primary target of vitamin E deficiency is the brain because it contains low amounts of vitamin E, and the vitamin E content of the liver acting as store decreases rapidly during the first week of life. Besides vitamin E, other components of the antioxidant system, e.g. the antioxidant enzymes (catalase and glutathione peroxidase) also have low activity in the brain as compared to other major tissues. The brain is highly susceptible to oxidative stress because of the accumulation of polyunsaturated fatty acids. The third source of free radical generation is the toxic level of different feed ingredients, e.g. toxicoses caused by vitamin A, selenium, and ionophore antibiotics. Other important aspects of antioxidants (e.g. vitamin E and selenium) in poultry are stimulation of the immune response (e.g. in the case of vaccination) and reduction of the risks of free radical formation as a result of macrophage function.
营养缺乏或营养紊乱会引发多种疾病，且其产生方式多种多样。饮食中特定营养素的含量可能不足以满足需求，饮食中可能含有使营养素失活或抑制其吸收/利用的物质，或者饮食与环境因素的相互作用可能扰乱新陈代谢。一般来说，脂质过氧化或氧自由基的产生是细胞代谢、分裂和分化以及激素和前列腺素生物合成的重要生理过程。通过这些过程产生的自由基会被抗氧化防御系统有效清除。该系统紊乱导致的脂质氧化失控可能在一些重要的家禽疾病和中毒中起关键作用。机体脂质过氧化物负荷的第一条途径是通过饲料，比如通过氧化脂质。氧化脂肪酸主要以不饱和酮化合物的形式从肠道吸收，并在组织中引发脂质过氧化。第二个问题是饲料中抗氧化剂含量不足，例如维生素E缺乏。营养性脑软化是家禽生产中的一个问题，它既取决于实际的维生素E供应，也取决于饮食中多不饱和脂肪酸的含量。在幼禽中，维生素E缺乏的主要靶器官是大脑，因为大脑中维生素E含量低，且作为储存器官的肝脏中的维生素E含量在幼禽出生后的第一周会迅速下降。除了维生素E，抗氧化系统的其他成分，比如抗氧化酶（过氧化氢酶和谷胱甘肽过氧化物酶），与其他主要组织相比，在大脑中的活性也较低。由于多不饱和脂肪酸的积累，大脑对氧化应激高度敏感。自由基产生的第三个来源是不同饲料成分的毒性水平，例如维生素A、硒和离子载体抗生素引起的中毒。家禽体内抗氧化剂（如维生素E和硒）的其他重要作用包括刺激免疫反应（如在疫苗接种的情况下）以及降低巨噬细胞功能导致的自由基形成风险。
