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Sheep farming
綿羊養殖
Turning the worms
改變蠕蟲
Gut bacteria may help fight nematode infestations in sheep
腸道細菌可以幫助綿羊抵御線蟲的侵襲
Sheep farmers in Australia and New Zealand have a problem.
澳大利亞和新西蘭的牧羊人有一個問題。
Their charges are susceptible to intestinal nematode worms which cause them to waste away and can, in severe cases, kill them.
他們的羊群容易受到腸道線蟲的影響，這些蠕蟲會使它們日漸消瘦，在嚴重的情況下，會令它們死亡。
Over the years, the worms have evolved resistance to drugs once used to attack them.
多年來，這些蠕蟲已經對曾經攻擊它們的藥物產生了抗藥性。
But a second approach is to breed countermeasures into the sheep themselves.
但第二種方法是在綿羊體內培育對策。
This can be done by counting the number of worm eggs in animals’ droppings and selecting as sires and dams those that have the fewest, on the assumption that these are the sheep with the least worm-friendly guts, and that this property will show up in their offspring as well.
這可以通過計算動物糞便中的蟲卵數量，并選擇那些蟲卵最少的作為公羊和母羊培育后代，假設這些羊的腸道對蟲子最不友好，這種特性也會在它們的后代中表現出來。
That works.
這很管用。
But how, has been obscure.
但如何做到這一點還是個未知數。
A study just published in Animal Microbiome, by Erwin Paz of the University of Western Australia and his colleagues, throws light on the matter.
西澳大利亞大學的Erwin Paz和他的同事剛剛在《動物微生物組》上發表的一項研究揭示了這一問題。
It suggests that what is being bred for is a propensity to develop a worm-hostile gut microbiome.
這表明，繁殖的目的是為了培養一種對蠕蟲不利的腸道微生物群。
Gut microbial health, once a fringe medical interest, is now mainstream for human beings, as bugs in the alimentary canal are linked with conditions ranging from obesity to arthritis.
腸道微生物健康曾經是醫學界中的冷門領域，但如今已成為人類醫學研究的主流方向，因為消化道中的細菌與肥胖、關節炎等一系列疾病有關。
But what is true of people is true of other animals, too.
對人類來說是這樣的，對其他動物也是這樣。
And, in the case of sheep, Dr Paz and his collaborators seem to have hit the jackpot.
在綿羊的例子中，Paz博士和他的合作者似乎大獲成功。
Dr Paz knew from past work that sheep with severe worm infestations tend to have abnormal bacterial populations in their faeces.
Paz博士從過去的工作中了解到，患有嚴重蠕蟲感染的綿羊的糞便中往往細菌種群不正常。
This led him to wonder whether the bugs in the guts of resistant sheep were somehow hampering the worms’ activities.
這讓他很好奇，抗蠕蟲綿羊腸道中的細菌是否以某種方式阻礙了蠕蟲的活動。
He and his team therefore looked at a flock of 200 sheep at a farm in Western Australia and selected ten that had particularly high loads of worm eggs in their faeces (1,940 per gram, on average) and ten that had low loads (410 per gram).
因此，他和他的團隊研究了西澳大利亞一個農場的200只綿羊，選擇了10只糞便中蟲卵含量特別高的羊(平均每克含1940只蠕蟲)和10只蟲卵含量低的(每克含410只蠕蟲)。
These unfortunate sacrificial beasts were then slaughtered and their entrails examine -- not for auguries of the future but for their microbial populations.
這些不幸的綿羊隨后被屠宰，并檢查了它們的內臟——不是為了預示未來，而是為了檢查它們體內的微生物種群。
As they had hoped to, the researchers did indeed find systematic differences between the microbiomes of the two groups.
正如他們所希望的那樣，研究人員確實發現了兩組微生物群之間的系統性差異。
These differences were particularly notable in the small intestine, where the worms live, with resistant sheep having richer and more diverse bacterial populations in this part of the gut than vulnerable animals did.
這些差異在蠕蟲生活的小腸中尤為明顯，與易受感染的動物相比，抗蠕蟲綿羊在腸道的這一部分擁有更豐富和更多樣化的細菌種群。
In particular, the team noticed that populations of bacteria which ferment carbohydrates such as cellulose and turn them into short-chain fatty acids were especially abundant in the resistant animals.
特別是，研究小組注意到，在抗蠕蟲綿羊體內，可將其轉化為短鏈脂肪酸的發酵纖維素等碳水化合物細菌種群尤其豐富。
It is, of course, possible, that the worms are affecting the sheep’s microbiomes, rather than the other way around.
當然，有可能是蠕蟲影響了綿羊體內的生物群，而不是體內生物群影響了蠕蟲。
But Dr Paz thinks this is unlikely, because all of the sheep looked at had at least some worms.
但Paz博士認為這不太可能，因為所有被觀察的綿羊都或多或少有一些蠕蟲。
Rather, he suspects, genetically resistant sheep are providing an intestinal environment conducive to bacteria which either produce compounds that repel the worms or consume resources which the worms depend upon.
相反，他懷疑，具有基因抗性的綿羊正在提供一個有利于細菌的腸道環境，這些細菌要么產生驅除蠕蟲的化合物，要么消耗蠕蟲所依賴的資源。
If that is correct, it opens up a third approach to worm control, which is to employ probiotics to shape the gut microbiomes of flocks directly, rather than relying on selective breeding to do it at one remove.
如果這個猜想正確的，它開辟了第三種控制蠕蟲的方法，即使用益生菌直接塑造羊群的腸道微生物群，而不是依賴于選擇性繁殖一次完成。
