Science发表的一项新研究表明，给奶牛的饲料简单添加一点东西就可能大量减少甲烷的排放，而甲烷正是导致地球变暖的温室气体之一。全世界每年由反刍牲畜产生的甲烷对地球气候变暖所起的作用相当于21亿吨二氧化碳的效果，为与人类活动相关的温室气体排放量的4%还多一点。这让奶牛成为甲烷减排的诱人目标。在一项新研究中，研究人员将化学物3- nitrooxypropanol——也称为3NOP——添加到84只生产牛奶的荷斯坦牛的饲料中，它们的饲料是以玉米和苜蓿为基料的，并连续12周监测它们的甲烷产量——这是在泌乳牛身上所做的规模最大、耗时最长的此类试验，科学家们说。对于那些饲料里含有3NOP的奶牛来说，甲烷排放量平均下降了30%，研究人员昨天在《美国科学院学报》在线版报道了这项研究。排放量的下降在试验的头两周发生，并持续了整个测试阶段，研究人员说。该添加剂似乎并没有影响到奶牛的胃口，也没有影响到奶牛产奶或者是奶牛所产牛奶的构成。而由于3NOP加强了饲料中营养物质的消化率，接受添加物补给的奶牛实际比那些没有接受补给的奶牛更重了。研究人员承认，需要更大型的测试从而来检查在长期条件下是否会有不利影响的突然出现，但3NOP的确是一种很有前途的甲烷减排添加剂。在以往的短期测试中，这种化学物已经帮助减少了绵羊和肉牛、以及非泌乳牛的甲烷排放。

原文链接：

Antiburp compound could reduce methane emissions from cows

原文摘要：

A simple supplement to a cow’s feed could substantially decrease a major source of methane, a planet-warming greenhouse gas, a new study suggests. Each year worldwide, the methane produced by cud-chewing livestock warms Earth’s climate by the same amount as 2.1 billion tons of carbon dioxide, a little more than 4% of the greenhouse gas emissions related to human activity. That makes cows tempting targets for methane reduction efforts. In a new study, researchers added the chemical 3-nitrooxypropanol, also known as 3NOP, to the corn-and-alfalfa-based feed of 84 milk-producing Holsteins and monitored their methane production for 12 weeks—the largest and longest such trial of its type in lactating cows, the scientists say. For cows whose feed included 3NOP, methane emissions dropped, on average, by 30%, the researchers reported online yesterday in the Proceedings of the National Academy of Sciences. The decline in emissions occurred during the first 2 weeks of the trials and persisted throughout the test, the researchers say. The additive didn’t seem to affect the cows’ appetite, nor did it affect either the production or the composition of the cows’ milk. And because 3NOP boosted the digestibility of nutrients in the feed, the cows that received the supplement actually gained more weight than cows that received none. Larger tests will be needed to see if detrimental effects crop up over the long term, the researchers admit, but in the meantime 3NOP is a promising methane-cutting additive. In previous short-term tests, the chemical has trimmed methane emissions in sheep and beef cattle as well as in nonlactating dairy cows