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首页> 外文会议>International Symposium on the Nutrition of Herbivores(ISNH-7); 20070917-22; Beijing(CN) >Nutritional control to reduce environmental impacts of intensive dairy cattle systems
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Nutritional control to reduce environmental impacts of intensive dairy cattle systems

机译：营养控制以减少集约化奶牛系统对环境的影响

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摘要

Demand for milk and meat is expected to increase rapidly. In the absence of major corrective measures, the environmental impact of cattle production will worsen. In this review, dairy cattle nutrient flows and nutrient accumulation are described by looking at nitrogen (N), phosphorus (P) and methane (CH4) emissions and mitigation options to limit or minimize nutrient loading in the environment. The efficiency of conversion of feed N into milk N is highly variable. Almost all the avoidable N losses is excreted in urine, which is of particular concern with respect to environmental impact. A rational reduction in N intake per cow, with minimal negative effects on lactating performance, will decrease urinary N excretion. This requires a proper balance between energy and N sources at rumen and post-rumen level. At the rumen level, reducing the N to energy ratio or reducing protein degradation rate are promising options. Splanchnic tissues have a high metabolic activity and remove a variable part of the amino acids available for absorption. However, quantitative knowledge on post-rumen N metabolism is limiting, and current protein evaluation systems appear unable to support decision making with a view to reduce N losses. Surplus P is largely excreted in faeces. The variation in efficiency of conversion of feed P into milk P is considerable. Current recommended dietary P concentrations have a large safety margin and reductions in P intake are possible without detrimental effects on animal production and health. Similar to N efficiency, P efficiency of the cow improves when more energy dense diets are fed. Several nutritional strategies have been proposed to reduce CH4 emissions. Among these, shifting from sugars towards starch in the diet, shifting from cell wall material towards starch, or feeding starch sources more resistant to rumen degradation all lead to substantial reductions in CH4 production per unit of rumen digested substrate. Although a number of feed additives have been shown to decrease CH4 production in vitro effectively, data on long-term in vivo effects are scarce. Variation at animal level in losses of N, P and CH4 is considerable. Proper integration of the various subsystems (soil, plant, animal) into a whole farm model requires appreciation of animal variation. Results from current farm system evaluations appear unsatisfactory in this respect. Finally, much more consideration of the interactions between losses of N, P and CH4 is required. In particular, nutritional management to reduce N losses has variable effects on methane emissions of dairy cattle.
机译：预计牛奶和肉类的需求将迅速增长。如果没有重大的纠正措施，牛的生产对环境的影响将会恶化。在这篇综述中，通过查看氮（N），磷（P）和甲烷（CH4）的排放以及缓解方案以限制或最小化环境中的养分含量来描述奶牛的养分流量和养分积累。饲料N转化为牛奶N的效率变化很大。几乎所有可避免的N损失都通过尿液排出，这对环境影响尤为重要。合理减少每头牛的氮摄入量，对泌乳性能的负面影响最小，将减少尿中氮的排泄。这要求瘤胃和瘤胃后水平在能量和氮源之间保持适当的平衡。在瘤胃水平，降低氮与能量之比或降低蛋白质降解率是有前途的选择。内脏组织具有高代谢活性，并去除了可吸收的氨基酸的可变部分。但是，关于瘤胃后氮代谢的定量知识是有限的，当前的蛋白质评估系统似乎无法支持决策以减少氮的损失。多余的P在粪便中大量排出。饲料P向牛奶P的转化效率变化很大。当前推荐的膳食中P的浓度具有很大的安全余量，并且可以减少P的摄入量而不会对动物的生产和健康造成不利影响。与氮效率相似，当饲喂更多能量密集型日粮时，母牛的磷效率会提高。已经提出了几种减少CH4排放的营养策略。其中，从饮食中的糖类向淀粉类转变，从细胞壁材料向淀粉类转变，或饲喂对瘤胃降解更耐受的淀粉源，均会导致每单位瘤胃消化底物的CH4产量大幅下降。尽管已显示许多饲料添加剂可有效地降低体外CH4的产生，但缺乏有关长期体内作用的数据。 N，P和CH4损失的动物水平差异很大。将各个子系统（土壤，植物，动物）正确集成到整个农场模型中，需要了解动物的变异性。在这方面，当前农场系统评估的结果似乎并不令人满意。最后，需要更多地考虑N，P和CH4损失之间的相互作用。特别是减少氮损失的营养管理对奶牛的甲烷排放有不同的影响。

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