Is stopping E. coli O157 contamination as easy as changing cattle diet?

That's certainly the claim in a new New York Times editorial (via The Frontal Cortex). The author, Nina Planck (author of Real Foods: What to Eat and Why), claims that it's as easy as just feeding cattle grass, and poof!--E. coli O157 will vanish.

More on this and why organic farming won't necessarily stop such outbreaks after the jump.

Planck writes:

Where does this particularly virulent strain come from? It's not found in the intestinal tracts of cattle raised on their natural diet of grass, hay and other fibrous forage. No, O157 thrives in a new -- that is, recent in the history of animal diets -- biological niche: the unnaturally acidic stomachs of beef and dairy cattle fed on grain, the typical ration on most industrial farms. It's the infected manure from these grain-fed cattle that contaminates the groundwater and spreads the bacteria to produce, like spinach, growing on neighboring farms.

In 2003, The Journal of Dairy Science noted that up to 80 percent of dairy cattle carry O157. (Fortunately, food safety measures prevent contaminated fecal matter from getting into most of our food most of the time.) Happily, the journal also provided a remedy based on a simple experiment. When cows were switched from a grain diet to hay for only five days, O157 declined 1,000-fold.

This is good news. In a week, we could choke O157 from its favorite home -- even if beef cattle were switched to a forage diet just seven days before slaughter, it would greatly reduce cross-contamination by manure of, say, hamburger in meat-packing plants. Such a measure might have prevented the E. coli outbreak that plagued the Jack in the Box fast food chain in 1993.

The problem is, however, that other researchers tried to reproduce the results from that 2003 study, and got mixed results. I and others did touch on this previousy here, and I'll also quote what I wrote over at The Frontal Cortex:

Not that simple. That's one study-others have found that feeding a corn diet actually decreased O157 survival compared to barley (J Food Prot. 2000 63:1467-74), or that when a long-term diet of hay was fed (greater than a month), the cattle still shed O157 (Appl Environ Microbiol. 2005 71:7974-9.) Another one found diet had no effect on O157 (J Anim Sci. 2006 84:2523-32). If anything's clear, it's that the link between diet and shedding of O157 *isn't* clear, despite what Plank claims.

I have a bit of first-hand knowledge of this, as one of my studies involves taking samples from cattle and growing E. coli out of it. In the place pictured, their cattle almost exclusively graze, supplemented with hay and a bit of corn. (Actually, now that I think about it, I'm not even 100% sure that they give *any* corn...) Anyhoo, we've isolated O157 from some of these grass-fed cows. So certainly, diet isn't a cure-all, and it's not necessarily even beneficial as far as carriage of O157 goes, despite the one paper Planck cites.

I've admittedly not read her book, but the summary of it makes me cringe a bit as a public health professional. Essentially, it seems to be a throwback to the good ol' days of eatin': pour on some more butter and bacon, don't pasteurize your milk (ugh), get your animals good and dirty. And indeed, a lot of posts I've read about this outbreak take a tone similar to hers: factory farming = necessarily bad and a hazard to health. Organic = necessarily good. This was a recent "As a Scienceblogger" question here that I didn't answer, simply because I don't have much of an opinion one way or the other on organic food; I don't necessarily think it's good or bad. I think there are a lot of reasons why it can be good (Janet mentions many of them here), but there are also a lot of reasons why I think it's over-sold and can even be worse for you than "regular" foods (such as some Sandra mentions here). Was this outbreak the result of careless "factory farming"? Was it the result of careless organic farming? (The company it's been traced to, Natural Selection Foods, is an organic farm). The answers are still rolling in, but I think it's a mistake to necessarily deride one form of agriculture or the other as universally being better, when there are positives and negatives about both.

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that is, recent in the history of animal diets -- biological niche: the unnaturally acidic stomachs of beef and dairy cattle fed on grain

Since you're cross-posting, I will too. The solution is obvious:
Rolaids for cattle.

(Yes, I am joking. Why do you ask?)

By somnilista, FCD (not verified) on 21 Sep 2006 #permalink

The currently suspected link (you may have already seen this) is the groundwater in the Salinas Valley, which as very high fecal coliform counts (as reported in the LA Times today. O157:H7 was positively id'd from a bag of spinach in the home of a sick person, providing the solid linkage.

The idea of altered diet for cattle is interesting. I'm completely unsurprised by the conflicting data (I'm sure you are too). Presumably, because O157:H7 is more acid-tolerant, it can pass through the more acidic stomach better, and therefore colonizes the intestinal lumen when non-pathogenic E. coli fail to make it through the stomach (or come through in lower numbers). So a better question might be if you started with a population of uncolonized cattle, varied the diets as described, do you get more or less accumulation of O157 in the gut than in a grain fed control. I haven't read any of the papers above, so I'd be curious if anyone had an expt. protocol like that. If they did, that's the study I would weight most heavily.

By Paul Orwin (not verified) on 21 Sep 2006 #permalink

The E. coli outbreak in Walkerton, ON back in 2000 (~2000 ill, 7 dead) was caused by grass-fed cattle. Sorry, Ms. Planck, it's not so simple.

I would't be too hasty to blame groundwater. Generally groundwater is protected by the subsurface conditions. That's not to say individual wells couldn't be and haven't been infected. However, that is usually an effect of surface conditions at the well site.

Well, whatever the investigation turns up it should be interesting.

By commissarjs (not verified) on 21 Sep 2006 #permalink

Certainly agree that it isn't as simple as switching to organic, but do question whether this has got anything to do with organic at all.

Earthbound may be organic, but it industrial organic, as far as I know, mostly feedlot corn fed. And I understood that the corn fed bit was largely the cause of increasing 0157 populations in the rumen, not the non-organic.

In fact I thought it was likely that organic feedlot is probably the worst for this sort of thing, as they can't dose the cows with preventative medicines and so on. And Plank, in the piece you quote above, does not refer to non-organic as being dodgy, but to industrial grain fed cattle - which can be organic or non-organic, at least in the States - being dodgy.

I mean, it says that Natural Selection says that its organic products have been cleared.

Big detail Ms. Plank missed. Spinach is not beef. If the spinach growers used manure from a feedlot operation as fertilizer, switching to grass 7 days before slaughter wouldn't have changed a thing.

just responding to the Rolaids quip, many dairy cattle rations contain sodium bicarbonate to buffer rumen pH, especially those with high levels of grain

By matt reising (not verified) on 23 Sep 2006 #permalink

Are there similar studies that show no link between corn-feeding and other diseases, or is it just O157?

The theory goes like this:

The cattles rumen is something like pH 7-8ish [or something, can't recall now it's been a while]. Feeding cattle hay or corn in their feed for rapidly buffing up their weight affects the rumen pH. The reason for this is bacteria in the rumen go crazy on the large amounts of starch in the feed and produce a large amount of acid as a byproduct. The acid lowers the pH of the rumen and kills off other bacteria that aren't acid tolerant. This killing off of the other bacteria provides less competition for the more acid tolerant O157:H7 E. coli, which then replicate to much higher numbers.

This leads to a greater contamination of farm stock by the organism, a higher overall bacterial load that gets into meat and such during slaughter and such forth.

I'm not sure if this is fully correct or not, but I believe it's a reasonable summary of the basic idea of what is going on. I personally would rather see a quantitative study being done rather than a diagnostic study. Finding a pathogen is one thing, but asking the question "How much of the pathogen is there" is what I'm interested in. Yes, you can find O157:H7 E. coli in cattle fed on grass as well, but how much of that organism can you find in said cattle vs. cattle that have been fed on a high starch/carbohydrate diet of hay and corn? That comparison is slightly more meaningful, because higher initial pathogen numbers make for a much easier time of infecting someone.

One of the things that is neglected in all of the discussion is the survival of O157:H7 outside of cattle (i.e., in secondary habitats such as water, soil, and predatory microorganisms). O157 seems to survive much better in these habitats in comparison to other E. coli. The idea that we're going to eliminate O157 is silly.

As far as I can tell, O157 appears to have a guerilla life history strategy sensu Harper. It reaches high densities in cattle, and never exists in a high percentage of cattle in a herd. Since it exists 'on the margins' to begin with, I wonder if trying to reduce its abundance and distribution further is a bit Sisyphean.

The only way I would think you could eliminate O157 is to lower herd sizes (and herd densitites) to the point of economic inviability for both organic and conventional farming; also, improving the 'hygiene' of the cattle would help, but this, too, is not feasible. This would lower transmission rates to a level at which O157 would be unable to sustain itself.

What a useful discussion!

It's true that grass-fed cattle can carry (and shed) O157. It's also true that it's markedly more prevalent in the acidic hind gut of grain-fed than grass (and other forage) fed cattle. It's also true that studies (including one by USDA, according to Jo Robinson of you're more likely to get sick from eating grain-fed than grass-fed meat.

Re the logical 'spinach does not equal beef' comment: The reason stopping grain in the last week of life would prevent illness is that reducing O157 before cattle are slaughtered would reduce cross-contamination of fecal matter and, say, burgers in meat packing plants. That would have an immediate (and positive) effect.

Of course cleaning up groundwater (as my NYT piece acknowledges) is a much longer and more expensive process. And there are yet other vectors of O157, such as house flies who carry it from cattle barns to human food; and human hands.

The study cited on The Frontal Cortex comparing corn and barley feeding and O157 prevalence is of course irrelevant b/c both are grains. The key factor is roughage - as found in grass and hay - and a low-acid hind-gut environment.

On 21 Sep, the LAT noted contamination of water in the Salinas Valley near 'grazing areas.' All cattle graze some in early life but industrial cattle are weaned sooner and fed grain sooner or more, than grass-fed cattle. Proper rotational grazing distributes manure properly and is unlikely to contaminate groundwater. Unregulated manure lagoons (despite relentless apologists for intensive farming methods) are vastly more likely to harbor and leach O157. Here in upstate NY, for ex, you don't even need a permit to dig a 1200 foot long shallow pit for liquid manure - even if it hits bedrock and ground water starts shooting up from the water table.

The Rolaids joke is relevant. Feeding bicarbonate of soda is, in fact, a remedy for chronic acidosis, the eventually fatal condition caused by grain-feeding. How much simpler to feed cattle as they were meant to eat in the first place!

The suggestion that feeding grass is not financially viable is belied by a number of facts: one,that the cost of inputs on grain farms is all but eliminated on grass farms. They include feed, fertilizer, antibiotics, steroids, and certain vet bills. Another is that the actual cost of these inputs - particularly oil to grow,fertilize, and ship grain - is considerably higher than farmers pay. I recommend anything by Richard Manning on this important eco-economic topic.

Beef and dairy are small-margin businesses, and many cattle farmers are just one higher-input-price increment away from unprofitability. Without subsidies most are not profitable at all.

Yet another cost is the 'externality' of paying to clean up ground water. (I've seen some intriguing possibilities for ecological cleaning methods, such as using UV-treated O2.)

Who pays for all this, from oil to corn to dirty water? The American taxpayer.

A number of farmers have shown that grass-farming is profitable. Dairy farmers in particuular benefit from replacing grain inputs with grass (which grows free, thanks to the sun). Don't forget that factory dairy cattle are also implicated in O157.

An argument about the safety of raw milk summarized by 'ugh' is, alas, unscientific. Dairy is a complex food - and an important one to understand properly, so I gave it a lot of space in the book. If you'd like to know more about milk but don't care to borrow REAL FOOD from the libary or buy it, you can read the dairy chapters on my site for free @

(I also recommend the links to experts who study these things and reading the books - especially on dairy - in my bibliography. If you doubt butter is good for you, for example, start to research dietary and blood cholesterol at I was astonished.)

Clean raw milk from healthy cows is quite safe. Pasteurization (though it was useful in the early 20th c, when urban dairies were unhygenic and cows were diseased) does not guarantee food safety. Listeria survives gentle pasteurization, and most dairy-related food poisoning cases occur in pasteurized products. Yes, Virginia, contamination can occur before or after pasteurizaton.

Cow health and safe handling practices are the most important factor in the safety of milk, not heat treatment.

I'm 8 months pregnant, by the way, and still eat raw milk cheese and drink raw milk. Why?

Because the sum of my research on traditional and industrial food production methods led me to this conclusion: I trust the traditional food chain more than the industrial food chain. Being a skeptical sort, in every case I look for objective evidence to back up my choices - and my advice.

Thus I am confident that reducing grain-feeding would reduce O157. I'm further confident that reducing grain-feeding would have other salutary effects: on cattle health, profitabilty of US agriculture, human health, and ecology.

Naturally, in a food web as complex as ours (as any food chain is) no single action will solve a problem like E coli. But what steps we can take, we should.

Thanks for the fine discussion!

Nina Planck