托福阅读水平的提升是一个循序渐进的过程，除了在备考过程中把握好TPO真题资料做好各类题型针对性练习与文章精读，我们还需要尽可能多的进行拓展阅读，提升对英文材料的熟练度和敏感度。拓展阅读材料一般应当选择难度与托福接近的内容，题材最好也能与常考高频话题相关。生物学是托福阅读常考话题之一，下面的这篇介绍蛋白质的双语素材难度适中，大家可以拿来作为很好的托福阅读辅助练习材料。

Protein-rich diets

Feed as well as food

As demand for protein grows, what people eat matters. So does what gets fed to animals

富含蛋白质的食谱

饲料与食物

随着人们对蛋白质需求的增长，吃什么变得很重要。给动物喂什么也同样重要

BETWEEN now and 2050 the planet’s population is expected to rise by a third, from 7.6bn to 9.8bn. Those extra mouths will need feeding(句型), and not just with staples(词汇). As people grow richer, their demand for protein rises, particularly for meat and fish. Beef consumption in Asia, for example, is expected to jump by 44% over the next decade alone. 从现在到2050年，全球人口预计将增长三分之一，从76亿增至98亿。这些新增人口需要养活，且不能光靠主粮。随着人们越来越富裕，蛋白质尤其是肉类和鱼类的需求上升。例如，仅在未来十年，亚洲的牛肉消费量预计就将增长44%。

Raising animals to be eaten already has huge effects on the world’s environment. The number of farm animals soared during the 20th century. More than 20bn chickens, 1.5bn cattle and 1bn sheep are alive today. A quarter of the world’s land is used for grazing them. They consume 30% of the world’s crops. They guzzle(句型)water—you need about 15,000 litres of the stuff to produce a kilo of beef, compared with only 1,500 litres for a kilo of maizeor wheat. And their eructations(词汇)do nothing for the climate. Livestock are responsible for 14.5% of all anthropogenic(词汇)greenhouse gases, according to the UN Food and Agriculture Organisation (FAO).饲养肉用动物已对世界环境产生了巨大的影响。二十世纪，农场动物(家禽家畜)数量剧增。目前全球有超过200亿只鸡、15亿头牛和10亿只羊。饲养这些禽畜占用了世界上四分之一的土地，消耗了全世界30%的农作物。它们还大量消耗水资源——每生产一公斤牛肉大约需要1.5万升水，而生产一公斤玉米或小麦只需1500升。这些动物的嗳气也对气候毫无益处。联合国粮农组织称，牲畜造成了14.5%的人为温室气体。

How then may the planet be fed sustainably? One set of answers revolves around convincing people to put different things on their plates. Vegetarians have the simplest solution of all, but try telling people in sub-Saharan Africa that they should stick to(句型)cassava. Encouraging people to eat more fish rather than more meat is a better answer. Human consumption of fish has now overtaken that of beef, and aquaculture accounts for half of all the fish people eat. But almost 90% of wild stocks are fished either at or beyond their sustainable limits. And farmed fish, particularly salmon, are often fed on smaller fish that themselves are caught at sea. A fashionable idea is for Westerners to eat more insects, which contain up to three times as much protein as beef and already form an integral or supplementary part of up to 2bn people’s diets, according to the FAO. But for that to happen, many will have to get over the “yuck”(词汇) factor. 那么，怎样才能可持续地为人类提供食物?有一套应对方案围绕着说服人们吃不同的食物展开。素食者的解决办法最简单，不过试试告诉撒哈拉以南非洲的人们应该只吃木薯会怎样。更好的答案是鼓励人们多吃鱼而不是多吃肉。人类对鱼类的消费量现在已超过牛肉，而这些鱼有一半来自水产养殖。然而，近90%的野生鱼类的捕捞量已达到或超过了可持续的限度。养殖鱼类，特别是三文鱼，经常被喂食从海里捕获的小鱼。一个时兴的想法是让西方人多吃昆虫。昆虫的蛋白质含量是牛肉的三倍(句型)，而且根据粮农组织的数据，昆虫已经成为20亿人饮食中不可或缺的部分或他们的补充食物。但要实现这一点，许多人将必须克服“恶心”的感觉。

Another set of answers involves using technology to create artificial protein. Investors such as Bill Gates and Richard Branson have backed artificial-meat startups that grow beef and poultry from animal cells. Tyson Foods, a meat processor, is an unlikely fan of plant-based proteins. Scientists are also looking at genetic modificationsto animals—to increase the muscle of cattle or to reduce infections among farmed fish. 另一系列答案涉及到运用技术来创造出人工蛋白质。比尔·盖茨和理查德·布兰森等投资者都资助了人造肉方面的创业公司，这些公司通过动物细胞培育牛肉和禽肉。出乎意料的(句型)是，肉类加工企业泰森食品公司也是植物性蛋白质的支持者。科学家们也在研究针对动物的基因改造技术，以提高牛的肌肉量或减少养殖鱼类的感染。

Innovations such as these have enormous potential, if they can be industrialised and win over wary consumers. But changing what humans eat is not the only route to feeding a growing population more sustainably. Another, less obvious, approach is to alter what animals themselves eat. It is here that technology may have the biggest impact soonest. 如果这样的创新能够工业化并赢得谨慎的消费者的支持(句型)，它们就有巨大的潜力。但是，要以更可持续的方式养活日益增长的人口，改变人类的饮食并非唯一途径。另一个不那么显而易见的方法是改变动物的饲料。正是在这方面，技术可能会以最快的速度产生最大的影响。

One source of improvement lies in the more efficient use of crops to feed animals. The proliferation of mills that process grain into feed is helping in places such as sub-Saharan Africa, for example. Data-intensive farming is helping improve agricultural yields of feed crops like soyabeans by carefully monitoring the use of water and fertiliser. 一个改进的途径是更高效地利用农作物来饲养动物。例如，在撒哈拉以南非洲等地，把谷物加工成饲料的工厂数量激增，对这些地区很有助益。通过仔细监测水和化肥的使用，数据密集型农业(词汇)能帮助提高大豆等饲料作物的产量。

Eat shit and diet

A more radical approach is to change animals’ diets. Efforts to reduce the amount of fish meal used in aquaculture have already paid dividends(句型). In 1990 90% of salmon feed used in Norway was fish meal, but by 2013 greater use of plant matter had reduced that figure to 30%. More can be done. At most 20% of protein in grains fed to animals is converted to edible protein; the rest is turned into waste products. Cargill, an agricultural giant, broke ground this year on the world’s largest gas-fermentation facility, in partnership with Calysta, a Californian firm that makes feed out of natural gas. After feeding bacteria called methanotrophs with methane, they can be turned into protein pellets(词汇)for fish and livestock. Insects are also an option. Flies and maggots can be raised on manure and organic waste, instead of grains, and then fed to cattle, chicken and fish.

奇特饲料

更激进的方法是改变动物的饲料。减少水产养殖中对鱼粉的用量已经产生回报。1990年，挪威90%的三文鱼饲料是鱼粉，但到2013年，植物性饲料用量的提高使这一数字降至30%。还有更多办法。在用来饲养动物的谷物中，最多只有20%的蛋白质转化为可食用蛋白质，剩下的则变成废物。农产品巨头嘉吉今年破土开建世界最大的天然气发酵工厂，合作伙伴是用天然气生产饲料的加州企业Calysta。用甲烷喂养被称为甲烷氧化菌(词汇)的细菌，可将它们转化为喂养鱼和家畜的蛋白颗粒。昆虫也是一个选择。苍蝇和蛆可以用粪便和有机废物饲养而无需谷物，然后再把它们喂给牛、鸡和鱼。

The FAO has warned that by 2050 the planet will need to produce 70% more food than it did in 2009. The idea of chomping on more bugs and eating lab-grown meat may capture the imagination. But the path to food sustainability also runs through animals’ stomachs.粮农组织警告说，到2050年，地球将需要生产出比2009年多70%的食物。大口嚼虫子和啃人造肉的想法可能会让人浮想联翩，但食物可持续性还需要靠(句型)改造动物的胃来实现。