The use of legumes under innovative grazing methods and strategic nutrients supplementation for cattle in tropical grazing systems

在创新放牧方法下使用豆类植物和为热带放牧系统中的牛提供战略性营养补充

• 批准号: 424144661
• 负责人: Dr.-Ing. Joaquin Castro
• 金额: --
• 依托单位: Fachgebiet Tierernährung und Weidewirtschaft in den Tropen und Subtropen (490i)
• 依托单位国家: 德国
• 项目类别: Research Fellowships
• 财政年份: 2019
• 资助国家: 德国
• 起止时间: 2018-12-31 至 无数据
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/424144661?language=en
• 关键词: use; legumes; under; innovative; grazing

Grasses are a main feed source for ruminants across the world. However, the productivity of grazing animals is commonly limited by a low supply of nitrogen (N), which hinders microbial protein synthesis in the rumen. The N supply under grazing systems can either be increased by incorporating legume species into the sward, by supplementing animals with concentrated N sources, or by a combination of both strategies. Legumes have been successfully incorporated into temperate grazing systems, but their incorporation into tropical systems has been less successful. This is related to the legumes’ susceptibility to trampling as well as to the preferential grazing of livestock for these species, which adds pressure to legumes. Additionally, pasture management strategies, which are adopted from exclusive grass swards based on the vertical defoliation of plants, can cause extreme defoliation of legumes, further limiting the incorporation of legumes into tropical grazing systems. In cases when legumes have been incorporated into the grazing system, an improvement in the nutritional status of animals has become clear, but, because of the preferential grazing by animals evidence of N wastage has been observed, a development opposite to the aim of efficiently using natural resources.Therefore, the aims of this research are i) to evaluate an innovative rotational grazing management based on the horizontal utilization of pastures in mixed legume-grass swards, and ii) to the study the interactions between N supplementation and the forages available in the pasture on the digesta kinetics of grazing cattle.For this, in a first study Zebu bulls will graze on experimental plots of only grasses or mixed legume-grass swards. A rotational scheme based on the horizontal proportion of un-grazed pasture will be compared with a control rotation scheme based on pasture height. The n-alkanes marker method will be used to estimate total intake and the proportion of each species consumed. A second trial with Zebu bulls grazing in sole grass or grass- legume tree pastures and supplemented with organic or inorganic sources of N will evaluate the fractional outflow rate of solid and liquid rumen digesta. This will be done by fitting the bulls with a peristaltic pump to constantly infuse Chromium and Ytterbium –markers for the passage rate - during grazing. Microbial protein synthesis and diet selection will be estimated from the purine derivatives excretion, and the n-alkanes methodology, respectively. The research will produce a better understanding of the plant × animal interactions during grazing of mixed legume-grass swards; it will also provide an improved pasture management strategy for a successful incorporation of legumes into tropical grazing systems. Moreover, important understanding will be generated on the physiological responses of the rumen dynamics of cattle, when grazing on mixed legume-grass swards, as affected by the characteristics of the supplemental N.

草是世界各地反刍动物的主要饲料来源。然而，放牧动物的生产力通常受到氮 (N) 供应量低的限制，这阻碍了瘤胃中微生物蛋白质的合成。放牧系统下的氮供应可以通过将豆科植物纳​​入草地、为动物补充浓缩氮源或两种策略的结合来增加。豆科植物已成功地纳入温带放牧系统，但纳入热带系统却不太成功。这与豆科植物对践踏的敏感性以及这些物种的牲畜优先放牧有关，这增加了豆科植物的压力。此外，基于植物垂直落叶的专有草场采用的牧场管理策略可能会导致豆科植物极度落叶，进一步限制豆科植物纳​​入热带放牧系统。当豆科植物被纳入放牧系统时，动物的营养状况得到明显改善，但是，由于动物优先放牧，观察到了氮浪费的证据，这种发展与有效利用自然资源的目标背道而驰。因此，本研究的目的是i）评估基于豆科牧草混合草地牧场水平利用的创新轮牧管理，和 ii) 研究氮素补充和牧场中可用饲料之间的相互作用对放牧牛食糜动力学的影响。为此，在第一项研究中，瘤牛将在纯草或混合豆科草丛的实验田上放牧。将基于未放牧草场水平比例的轮作方案与基于草场高度的控制轮作方案进行比较。正烷烃标记法将用于估计总摄入量和每个物种消耗的比例。对在单一草或草豆科树牧场放牧并补充有机或无机氮源的瘤牛进行的第二次试验将评估固体和液体瘤胃消化物的部分流出率。这是通过给公牛安装蠕动泵来在放牧期间不断注入铬和镱（通过率的标记）来完成的。微生物蛋白质合成和饮食选择将分别根据嘌呤衍生物排泄和正烷烃方法来估计。该研究将更好地了解豆科牧草混合草场放牧期间植物与动物的相互作用；它还将提供改进的牧场管理战略，以便将豆科植物成功纳入热带放牧系统。此外，当牛在豆科牧草混合草丛上放牧时，受补充氮特性的影响，对牛瘤胃动态的生理反应也将产生重要的了解。