DEVELOPING RICE STRAW FOR ANIMAL FEED

每年有数亿吨的稻草和谷壳在田里被烧掉，只是为了摆脱它们。这种燃烧通过释放黑碳颗粒、甲烷（和更大的挥发性化合物）、一氧化碳和臭氧的产生导致非常糟糕的空气质量。在它们之间，这些排放导致呼吸道疾病和暴露人群的过早死亡，由于臭氧的毒性作用和黑碳的遮蔽而导致作物产量的重大损失，以及加剧全球变暖，特别是由于甲烷和黑碳。如果能找到稻草的替代用途，所有这些负面影响都是可以避免的。由于稻草质量差，目前很少用作动物饲料。稻草由大约75%的多糖组成，这可以作为动物饲料提供相当大的价值，不幸的是，这种稻草目前很难消化，部分原因是其木质素含量，更重要的是因为稻草具有高含量的二氧化硅。二氧化硅可以占稻草干重的10%，这不仅使其难以消化，而且非常难吃。本项目的总体目标是寻找提高作为动物饲料的稻草质量的方法，使其从燃烧转变为生产肉类和乳制品的宝贵资源。我们一直在研究稻草作为通过发酵其成分多糖生产生物燃料的潜在原料。与稻草用于动物饲料一样，这一过程也受到稻草消化率的挑战，我们一直在使用全基因组关联研究（GWAS）来识别参与使稻草难以消化的基因和可用于育种研究以改善这一特性的分子标记。在这项工作中，我们为在越南收集和种植的170种不同的水稻品种制作了详细的遗传图谱。我们已经测量了来自这些品种的秸秆被商业消化酶（纤维素酶）消化的程度，并且还测量了它们的二氧化硅和木质素含量。这表明，一些品种比其他品种的可消化性高四倍以上，并且一些更易消化的品种中的二氧化硅含量低于1%。在这里提出的工作中，我们希望扩大这些研究，以研究水稻多样性小组的秸秆在动物饲料质量方面的特点。这将在英国的实验室中以高通量的方式完成，以便我们能够进行GWAS来识别标记，以帮助在商业品种中培育改良秸秆，并帮助我们识别影响这些特征的新基因。在科学层面上，我们将通过寻找影响二氧化硅含量的细胞壁相关基因，进一步了解二氧化硅对秸秆消化率的影响。从研究对秸秆利用产生真实的影响的角度出发，我们将与越南和菲律宾的科学家合作，展示秸秆改良的潜在价值。我们将通过识别具有对比动物饲料价值（高和低）的水稻品种子集并将其用于使用carabao的饲养试验来做到这一点。卡拉宝是东南亚传统上用作驮畜的水布法罗，目前正在热带国家开发用于肉类和乳制品生产。这些试验的结果将证明使用更高质量的秸秆作为动物饲料的好处，我们将利用这些信息教育农民种植粮食和动物饲料生产两用水稻品种的好处，以及提高商业品种秸秆价值的好处。从长远来看，我们的工作有可能改善稻米种植国的环境和人民的福祉，增加农民收入，并为当地消费提供高蛋白产品。

Hundreds of millions of tons of rice straw and husks are burned in the field every year simply to get rid of them. This combustion causes very bad air quality through the release of black carbon particles, methane (and larger volatile compounds), carbon monoxide and the generation of ozone. Between them, these emissions cause respiratory illness and premature death in exposed populations, significant losses in crop yield due to the toxic effects of ozone and shading by black carbon, and increased global warming, especially due to methane and black carbon. All of these negative impacts are avoidable if alternative uses for rice straw can be found. Rice straw currently finds little application as animal feed because of its poor quality. Rice straw is composed of roughly 75% polysaccharides and this can provide considerable value as animal feed, unfortunately, this straw is currently hard to digest, partly due to its content of lignin, and more importantly because rice straw has a high content of silica. Silica can make up to 10% of the dry weight of rice straw and this not only make it hard to digest but also highly unpalatable. Our overall aim for this project is to find ways to improve the quality of rice straw as animal feed in order to move it from being burned to becoming a valuable resource for the production of meat and dairy products.We have been studying rice straw as a potential feedstock for producing biofuels by fermentation of its component polysaccharides. As in uses of rice straw for animal feed, this process is also challenged by straw digestibility and we have been using genome-wide association studies (GWAS) to identify genes that are involved in making straw hard to digest and molecular markers that can be used in breeding studies to improve this characteristic. For this work we have made detailed genetic maps for a collection of 170 diverse rice accessions collected and grown in Vietnam. We have measured how well the straw from these varieties is digested by commercial digestive enzymes (cellulases) and also measured their content of silica and lignin. This revealed that some varieties are more than four times more digestible than others and that silica content in some more digestible varieties are lower than 1%. In the work proposed here, we wish to expand these studies to examine the characteristics of straw from the rice diversity panel in terms of animal feed quality. This will be done in a high-throughput manner in the laboratory in the UK in order to allow us to carry out GWAS to identify markers to help in breeding for improved straw in commercial varieties and to help us identify new genes that affect these characteristics. On a science level, we will focus on increasing our understanding of how silica affects straw digestibility, by looking for cell wall-related genes that affect silica content.From a point of view of seeing our studies have real impacts on straw use, we will work with scientists in Vietnam and the Philippines to demonstrate the potential value of straw improvement. We will do this by identifying a subset of rice varieties with contrasting animal feed value (high and low) and using these in feeding trials using carabao. Carabao are water buffalo traditionally used as draft animals in South East Asia that are being developed for meat and dairy production in tropical countries. The results of these trials will demonstrate the benefits of using higher quality straw for animal feed and we will use this information to educate farmers of the benefits of growing dual purpose rice varieties for grain and animal feed production, and rice breeders of the benefits of improving straw value in commercial varieties. In the long term our work has the potential to improve the environment and well-being of people in rice growing countries as well as increasing farmer income and the availability of high protein products for local consumption.