氧化亚氮（N2O）是高强度温室气体及破坏地球大气臭氧层的关键成分。肉牛粪尿在贮放或作为肥料施用过程中产生大量N2O。减少肉牛N2O排放对保护地球环境意义重大。硫代葡萄糖苷(glucosinolates, GLs)是十字花科植物(Brassica spp.)的特有成分。该成分在硫代葡萄糖苷水解酶(myrosinase)作用下可水解成异硫氰酸酯 (isothiocyanates, ITCs)等成分。现有结果表明，ITCs能够显著抑制N2O生成的关键步骤，而采食十字花科牧草的肉牛粪尿的N2O产量显著低于其他牧草。因此推测，采食十字花科牧草的肉牛可能从尿中排泄ITCs等代谢产物，抑制了N2O生成。而ITCs能否通过肉牛尿液排泄，尚不清楚。本项目拟研究肉牛对菜籽饼GLs的代谢规律，阐明肉牛对菜籽饼GLs代谢产物ITCs的排泄规律及抑制N2O生成的效果，为通过饲喂肉牛菜籽饼抑制N2O生成奠定理论基础。

Nitrous oxide (N2O) is a potent greenhouse gas as well as the key component depleting the ozonesphere of the earth. The excreta of beef cattle produces a large amount of N2O during storage or when used as fertilizer. It is of great importance to mitigate N2O emission from excreta of beef cattle. Glucosinolates (GLs) are specific components of Brassica plants. GLs can be hydrolyzed to isothiocyanates (ITCs) and other products by myrosinase. Present results show that ITCs significantly inhibit a key process of nitrification for N2O formation, and the N2O emission from the excreta of beef cattle fed with brassica grass is significantly lower than other grass. It is speculated that ITCs are excreted from the urine of cattle and consequently inhibit the N2O formation. However, it is unclear if ITCs are actually excreted in the urine of beef cattle. The objetcives of the project are to study the metabolism of rapeseed meal GLs by beef cattle, to clarify the excretion pattern of GLs metabolites from beef cattle and the inhibition effect on N2O from excreta, and estabolish the theretical basis of inhibiting N2O formation through feeding rapeseed meal to beef cattle.