畜禽饲料源微量元素营养代谢和排放规律研究进展

Advances in nutrient metabolism and emission of livestock and poultry dietary trace elements

微量元素是动物必需的营养素,也是植物-动物-土壤循环中的关键因子.畜禽饲料微量元素营养与动物生长发育、健康状况和繁殖性能密切相关.由于饲料源微量元素的利用率较低,为提高畜禽养殖的生产效率和畜禽产品营养价值,饲料源微量元素可能存在过量添加.一方面,畜禽产品的营养价值随微量元素沉积增加而大幅度提升;另一方面,未被动物利用的微量元素随粪便排出,对养殖场周边的土壤、水源等造成巨大污染.我国是畜禽养殖大国,也是畜禽产品的消费大国,厘清饲料源微量元素的营养代谢和排放规律,并提出相应的解决方案,对提升养殖业经济效益、保护养殖生态环境、促进养殖业健康可持续发展具有重大意义.因此,本文综述了微量元素在体内的营养作用和吸收代谢机制、畜禽产品中富集特征和粪便排放规律,探讨了适当降低日粮中微量元素添加水平、改善添加剂型和种养结合模式可能是畜禽养殖微量元素污染问题的良好解决方案.

Trace elements,including iron,copper,manganese,zinc,selenium,and iodine,comprise less than 0.01%of animals,yet are essential nutrients and key factors in the plant-animal-soil cycle.Trace elements have important physiological functions and are often required for enzymatic reactions,energy metabolism,and synthesis of materials,immune defense,and other activities necessary for life.Micronutrient deficiency causes developmental disorders and decreased immunity in young animals,and even leads to nutritional metabolic diseases and death.Supplementation of the diet of livestock and poultry with trace elements is closely related to growth and reproductive performance.Many studies have demonstrated that dietary supplementation with trace elements improves production performance and the content of these elements in livestock and poultry products.Due to the low bioavailability of dietary trace elements,excess trace elements may be added to livestock and poultry diets.However,animals generally have self-regulatory mechanisms of absorption and metabolism to maintain the homeostasis of trace elements.Excess dietary trace elements that are not absorbed are discharged in the excrement and pollute farm soil and water sources.In particular,heavy metals,such as copper,zinc,manganese,chromium,and cadmium,detrimentally affect the growth of crops and change the composition and structure of soil microorganism.Human health can also be affected when heavy metals bioaccumulate through the food chain.Breeding and consumption of livestock and poultry occur on a large scale in China,the excrement from livestock and poultry is an important source of heavy metals in the environment.Soil,water,and crops in most areas of China are seriously affected by heavy metal pollution.Clarifying the nutrient metabolism and emission of dietary trace elements to reduce environmental contamination is crucial to improve the economic benefits of breeding,protect the ecological environment of breeding areas,and promote the healthy and sustainable development of the breeding industry.In recent years,increasing attention has focused on reducing environmental pollution caused by heavy metals from livestock and poultry,while maintaining the efficiency of breeding production.Appropriate reductions of trace elements in livestock and poultry diets do not impact growth performance and reduce the content of trace elements in excreta.In addition,organic trace element additives demonstrate higher bioavailability with less emission.This article summarizes the nutritional function,absorption and metabolism mechanism,enrichment characteristics of livestock and poultry products,and fecal excretion patterns of trace elements.The appropriate lower levels,improved dosage form of supplemented dietary trace elements,and a model of combined planting and breeding may alleviate trace element pollution in livestock and poultry breeding.