Brains vs Grains

September 19, 2007 5:33 AM

What is the most energy efficient form of flesh to eat?

I've got a veggie friend who doesn't eat meat largely because it's a better use of natural resources to eat the vegetation yourself than to feed it to animals and then eat them.

Ignoring the validity (or not) of this statement, I was wondering how the different meats stack up and how efficient they are at providing fuel to humans.

I guess the question ultimately is "how much energy does it take to get a cow/pig/chicken/whatever to maturity and how much can be gained from eating the flesh."

For the sake of simplicity, I guess we have to assume the vegetation is all natural, the animals aren't in centrally heated houses and no energy is expended getting the recently dead flesh to the dinner table...

posted by twine42 to science & nature (38 comments total)

You'll find there's a reason why we raise the livestock we do. For instance, the question's premise is flawed because we don't eat the same diet as cows. The energy required to raise that meat may exceed the net gain from it, but it's a bonanza of a profit if you exclude all foods the cow eats that we can't process.
posted by cellphone at 5:51 AM on September 19, 2007

Mollusks
Insect/Crustacea
Fish
Foul/reptile/amphibian
Small mammal
Large Mammal
posted by Pollomacho at 5:53 AM on September 19, 2007

What pollomache said; invertebrates / cold-blooded things tend to comsume the least food themselves to grow, as they don't need to run our kind of hardcore metabolism to keep their internal temperatures up. Sessile things, as well.
posted by Jimbob at 5:56 AM on September 19, 2007

Wildlife in general, I would think. I mean, cut out out the middleman, go directly to the self raised meat machine. Cross bows, that sort of thing.
posted by IndigoJones at 6:07 AM on September 19, 2007 [1 favorite]

Pollomacho - would that need one to assume that all meat has the same energy returns?
posted by twine42 at 6:17 AM on September 19, 2007

Expanding on what cellphone said ... Practically everything we do is inefficient to some extent, thanks to the laws of thermodynamics. I mean, eating bread is less efficient than eating the grains directly, because energy is expended in the processing of bread. The catch is that even those who try to eat only that which we find 'naturally' often find it difficult to consume enough calories, since our digestive system is not, like the cow's, designed to eat grass. (We also generally do not spend a great deal of time grazing.) It is possible to view the cow as turning grass (ordinarily not a food we would get very much out of) into steaks. (Though that may seem a bit callous).
posted by Comrade_robot at 6:21 AM on September 19, 2007

Right. I tried vegetarianism for this same reason.

1) Venison (because there is no opportunity cost associated with using the land for a different purpose.)

2) Seconding fishies. Also, on the large animal list, you may want to separate herbivores from carnivores. Obviously, shark fin soup, bald eagle gumbo, and wolf sausage are not as efficient as herbivore meat.

3) Veal is an interesting question. Surely it's more efficient than other forms of beef.

And to cellphone, it's also the opportunity cost of using the land for somethiing else. If I could have planted soybeans instead of corn for cowfeed...
posted by Pants! at 6:29 AM on September 19, 2007

Here's part of the answer to your "ultimate" question: A UN report on raising livestock for food. Here's a summary from grist.org, which is a lot less than the full report's 300 pages.

The totally unattributed stats on the internet say that it takes about 2500 gallons of water to raise 1 lb of beef and about 25 gallons to raise 1 lb of wheat. Even though wheat is only 8-10% protein, that's still got to be a net loser.

The fossil fuel numbers are slightly better (not 2 orders of magnitude worse, only 1ish order of magnitude!): . Feedlot beef, the most inefficient meat, produces 1 calorie of food every 33 calories of fossil fuel consumed. That's compared to oats, which produce 2.5 calories for every 1 calorie of fossil fuels. Here's the totally unattributed source where I stole these NON-stats from. Thanks for citing your sources, crazy UPenn internet emag!

So that's a place to start. Raising meat is a huge loser for any of a number of inputs (food, fossil fuels, fertilizers, water), regardless of exactly how many calories come out of a pound of beef.

Also ask your friend if anyone, anywhere, has ever died of protein deficiency? Yeah, sure, people are malnourished in the developing world, and their diets consist almost entirely of vegetables. But vegetables, even wheat, oats, etc., contain LOTS of protein. It's not the protein their missing from their diets. You'd live a fine life if you ate a balanced diet of broccoli (also 8% protein) and other plants, as long as you include enough rice to get the few amino acids your body can't make... but even that has never killed anyone.
posted by zpousman at 6:37 AM on September 19, 2007 [1 favorite]

I would think rats would be high on the list. Their ability to sustain their population based solely on existing resources (i.e., trash) means they have less of an eco-footprint. Now, whether or not you consider rats meat is another question...
posted by grateful at 6:40 AM on September 19, 2007

Even taking into account what cellphone says, which is basically that animals turn energy we can't use (energy stored in grass) into energy we can (the energy stored in tasty tasty beef), I think it's still a large net loss.

A cow has to eat a lot of grass. And these days that grass is not wild growing "free" grass. It's corn, hay, alfalfa, and soybeans and other crops that are planted so that we can feed them to beef.

Water-dwelling animals that we don't feed (except for all those days fishing) are less susceptible to this argument. But those farm-raised catfish, salmon, and these days those penned in ocean fish are. I conjecture that most people who eat any appreciable meat in their diets do so at a (huge) net loss in energy.

Not so related to the question: For me, meat is a side and a rare indulgence even then. I'm a 99% vegetarian and I'm pretty happy with my choice. I'm trying to balance doing the right thing for my body and the environment, while still taking a nice bite of steak from a friend's plate every once in a while. My friends call me a cheetatarian.
posted by zpousman at 6:45 AM on September 19, 2007 [1 favorite]

Rabbit is the most cost-effective animal to raise for meat.
posted by ewagoner at 6:48 AM on September 19, 2007

I am only partway through it, but for an interesting discussion on this topic I recommend The Omnivore's Dilemma by Michael Pollan. In it he mentions that for factory-raised meat animals, it takes 4 pounds of corn to get 1 pound of beef. For chicken, it takes 2 pounds of corn to get 1 pound of meat. Breaking the math down another way, he calculated that it takes about a barrel of oil to get a steer to slaughter weight.

It is possible to view the cow as turning grass (ordinarily not a food we would get very much out of) into steaks. (Though that may seem a bit callous).

Actually, Pollan does exactly that, except it's corn in the factory animal universe.
posted by cabingirl at 6:50 AM on September 19, 2007

I know that farm-raised, algae-eating Tilapia is very high on the list.
posted by sourwookie at 7:04 AM on September 19, 2007

to eat the vegetation yourself than to feed it to animals and then eat them

you can only wish that the meat you find at the supermarket/butcher comes from grass-fed animals. unless stated otherwise they eat anything but -- corn, animal protein feed (you don't want to know from what it is rendered), anything else.

oh, and pigs usually drink their own (lightly diluted) waste, so I guess that makes them efficient.
posted by matteo at 7:08 AM on September 19, 2007

Rabbit is the most cost-effective animal to raise for meat.

only if you pump them full of antibiotics, because otherwise they'll drop like flies, no matter how much and how fast they breed. try to get your antibiotics for cheap and hope no one who'll eat your rabbits is allergic to antibiotics
posted by matteo at 7:09 AM on September 19, 2007

Assuming the vegetation grows naturally ruins the comparison. Almost nothing we eat grows naturally, that is, without a whole lot of fertilizers and cultivation.

I'm sure it's been stated upthread, but animals are eaten precisely because they're efficient producers of protein, usually from things that humans can't eat.

In terms of large animals, I would guess it'd go: wild game, pigs, goats, cows from most efficient to least, since cows eat almost exclusively human edible food (corn), wild game eats nothing that people eat (aside from the odd crabapple or my tomato plants), pigs can eat just about anything, likewise goats.
posted by electroboy at 7:15 AM on September 19, 2007

I wonder if birds, with their extremely high metabolism are actually very efficient.
posted by electroboy at 7:17 AM on September 19, 2007

how much energy does it take to get a cow/pig/chicken/whatever to maturity and how much can be gained from eating the flesh.

Throwing yet another politically-laden tangent into the mix:
One thing that is generally agreed to be higher on the energy-cost list than eating meat is car ownership. Thus more energy can be gained from eating flesh than is spent in raising it IF (big if) you are in the habit of using the extra energy you get from the higher-density food to fuel a bicycle, rather than using oil to fuel a car.

Of course, eating no meat and trying to cycle-commute would be more efficient still, but where I live, there are enough steep hills that cycling on an ideology-based diet isn't a trivial matter :-)
posted by -harlequin- at 7:29 AM on September 19, 2007

matteo: "[rabbits are efficient] only if you pump them full of antibiotics, because otherwise they'll drop like flies, no matter how much and how fast they breed. try to get your antibiotics for cheap and hope no one who'll eat your rabbits is allergic to antibiotics"

I've never known this to be the case, either with my own rabbits nor anyone I've known that has raised them for meat. Maybe because we go out of our way not to raise them in bacteria-laden living quarters, which is something most industrial meat producers can't claim.
posted by ewagoner at 7:38 AM on September 19, 2007

matteo writes "only if you pump them full of antibiotics, because otherwise they'll drop like flies, no matter how much and how fast they breed. try to get your antibiotics for cheap and hope no one who'll eat your rabbits is allergic to antibiotics"

This is just not true, at least on a small scale. My family has raised hundreds of rabbits for food (1-2 dozen at a time) and I don't think we've ever bought antibiotics.
posted by Mitheral at 7:51 AM on September 19, 2007

As mentioned by cabingirl above, of the farmraised critters, chickens are most efficient in turning feed into meat. You can pretty much equate energy with feed. According to this interview: 2.6 pounds of feed yields a pound of eggs, 4.8 pounds of corn feed yields a pound of cattle, 7-8 pounds yields a pound of pig (but I'm finding other sources that say 2.8-3.5 pounds of feed for pigs).

Wild critters like ocean-derived animals, venison, etc. are not necessarily more efficient than the chicken, but since no fuels are expended in feeding them, you could argue that eating them has less energy impact; but on the other hand overfishing is a serious environmental issue.

Also, I'm hearing about vegetarians who have decided grass-fed beef is OK, since people couldn't eat the grass, anyway.
posted by beagle at 8:14 AM on September 19, 2007

Seconding cellphone and cabingirl, but i'd say that the source of the energy used to raise the animal for slaughter has got to be as important to your friend's concerns as the efficiency of the conversion to food energy for human use.

Compare industrial beef production, which uses fossil fuel to produce fertilizer to grow corn to feed cows in a feedlot, with pasture-raised beef, where cows are fed on grasses grown using only free solar energy.
posted by Hlewagast at 8:21 AM on September 19, 2007

It seems like it would be most fuel-efficient for the diehard carnivorous humans to eat the vegetarian ones.
posted by misha at 8:28 AM on September 19, 2007 [1 favorite]

Like Michael Pollan says in The Omnivore's Dilemma, it would be so much more efficient if we could just drink the oil ourselves that powers the industrial food supply.
posted by Hlewagast at 8:46 AM on September 19, 2007

No data, but dormice (with honey! they were called gliris) were on the menu in ancient Rome. I imagine they were pretty efficient.

I wish an economist would publish a big huge paper on this subject...it's interesting! Right now there is literature, but no one paper that has the aggregation of the studies done.

Rabbits

If you have access to academic journals:
Beef Production Options and Requirements for Fossil Fuel
G. M. Ward; P. L. Knox; B. W. Hobson
Science, New Series, Vol. 198, No. 4314. (Oct. 21, 1977), pp. 265-271.

Energy supply patterns for finishing steers: feed conversion efficiency, components of bodyweight gain and meat quality
Meat Science, In Press, Accepted Manuscript, Available online 28 August 2007,
A.P. Moloney, M.G. Keane, M.T. Mooney, K. Rezek, F.J.M. Smulders and D.J. Troy

Growth, yield of carcass and biochemical composition of meat and fat in nutria (Myocastor coypus) reared in an intensive production system
Meat Science, Volume 76, Issue 2, June 2007, Pages 366-376
M.C. Cabrera, M. del Puerto, R. Olivero, E. Otero and A. Saadoun
posted by melissam at 9:02 AM on September 19, 2007

1-2 dozen at a time)

sounds like a goldmine.
posted by matteo at 9:10 AM on September 19, 2007

Better than gold as you can eat rabbits.
posted by Mitheral at 9:33 AM on September 19, 2007

There are two separate things being discussed here: raising animals industrially, and raising them on an old-style small farm. Isn't it Pollan who makes the argument that on a "traditional" farm (he uses the hippy farm in the southeast as an example, I think, with the mobile chicken coop and the pigs) the animals are extremely efficient, because they eat waste products from human-food crops, and some of their own waste products as well? And at the same time, their waste products provide the fertilizer that makes the crops we eat grow.

On the farm he describes, the cows eat grass, the chickens eat the bugs and worms from the cow poop, and the pigs do something, too -- maybe rooting up the soil to mix everything together? (I don't think he really gets into this, but I've seen both pigs and chickens eat lots of the "leftovers" from butchering, so there is additional efficiency that way, too.) So the answer to the question, on a small self-contained farm, is contained in the ratios of cows : chickens : pigs : acres of human crops. (Basically, lots of chickens, some pigs, a few cows.)

But the industrial process that produces the vast majority of the food we all eat, animal and vegetable, is totally different, with each piece separated from the others. The cows eat corn and live in big buildings and their poop goes into lagoons, for example, instead of pooping in the fields so that the chickens can eat the bugs in the poop and the poop can go into the ground. And since this is all driven by fossil fuels (for transport, heating, and fertilizing), the question posed about efficiency really matters, because finding a more efficient source of meat means less fossil fuels consumed. (Cue soundtrack to Soylent Green....)
posted by Forktine at 9:47 AM on September 19, 2007

Definitely farm-raised mussels. They don't require any food be given to them (they eat plankton) and they actually leave the water cleaner than when they started.
posted by TungstenChef at 10:50 AM on September 19, 2007

Pigs will happily eat most foodwaste, so lots of families kept a pig as an efficient garbage disposal that creates bacon. I've encountered a recycling system that collects food for pigs, so some people still do this. If you keep chickens and give them a yard to graze for bugs and stuff, they're pretty efficient. Meat from a retired egg-layer might be counted differently, and makes incredibly flavorful chicken soup.
posted by theora55 at 11:11 AM on September 19, 2007

I know that farm-raised, algae-eating Tilapia is very high on the list.

Make sure you know where your farm-raised tilapia come from. Fish imported from overseas are definitely not "using less resources". Unregulated (and very often regulated) fish farms cause pollution, and require fish to be fed a lot of antibiotics. It's worth investigating the source.
posted by oneirodynia at 11:11 AM on September 19, 2007

Lots of fishes turn more than 85% of the food they eat into raw body mass, which is kinda hot.

The trick with rabbits, and squirrels, and other extremely lean forms of meat is that it's actually possible to starve to death eating as much of them as you want, it's got a catchy name, but I think it's something like "rabbit starvation" or...something.
posted by TomMelee at 11:56 AM on September 19, 2007

A good rule of thumb is that 10% of the energy from one level of the food chain ends up in the next level.

So eating a herbivore will give you roughly 10% of the energy that you would get from eating all those veggies instead. Eating a Carnivore who eats that herbivore would give you only 1% of the energy that was in the veggies.

Again, this is a rough estimate, but it gives you a good idea of how much more efficient vegetarianism is. (and this is coming from a meat-loving omnivore)
posted by chrisamiller at 12:36 PM on September 19, 2007

So eating a herbivore will give you roughly 10% of the energy that you would get from eating all those veggies instead. Eating a Carnivore who eats that herbivore would give you only 1% of the energy that was in the veggies.

Just to note: this works if you are talking about modern industrial farming, where cows eat corn that could instead be made into corn syrup for big gulps or ground up into maseca for corn tortillas -- where the cow and you are competing for that corn, basically.

But if the cow eats something that you don't -- grass, say -- and if in the process of doing so it produces stuff (poop!) that makes the corn you eat grow better, then the situation is different.

In the real world, not many of us buy meat that comes from animals who come from that kind of farm. But if we did, the energy economics of meat eating would be a lot more in favor of being an omnivore.
posted by Forktine at 1:19 PM on September 19, 2007

In the real world, not many of us buy meat that comes from animals who come from that kind of farm.

I assume most of the people answering the questions here are Americans; I had no idea American agriculture had really gone so far down that path. Here in Australia, chickens and pigs tend to be raised on an industrial scale, but cows and sheep are still wandering the countryside eating the grass - sometimes improved pasture, in other parts of the country they're grazed in native bush (particularly in the cattle industry).

"Corn-fed beef" is considered a speciality item - everyday, normal beef is, by my understanding, still generally eating grass.

The end result of this seems to be that eating meat in Australia is more efficient and less environmentally destructive than eating meat in, say, the UK or America... which I find highly surprising given the nasty climate and nutrient-poor soils Australia has. Maybe it's just a matter of population density - if we had as many humans as America, we wouldn't have any space left to graze the wide open spaces anymore?
posted by Jimbob at 4:09 PM on September 19, 2007

Actually Jimbob, most beef in Australia these days is now feedlotted. There has been a massive change in the industry in less than a decade. Still for shorter periods than the US, and less intensively, but it's no longer totally correct to say that Aussie beef is distinctly different in that respect. It's much much easier to get superior grass-fed beef, but your typical Coles or Safeway foam pack will have spent some time finishing off in a feedlot. We don't do hormones though.

Lamb is still overwhelmingly grassfed, and nearly all from unirrigated pastures. Of course that sort of prime lamb country could be used for cereal cropping so I guess still doesn't meet efficiency criteria.

Kangaroo is wild grown and shot - that would have to be supremely efficient meat form many perspectives. High protein and the inputs are close to zero/negligible. I guess it would be sea or air freighted to North America however.

The original question is kinda odd - most environmentalists don't consider physical efficiency to be more than a part of the equation. The total impact could include GHG emissions (bad for methane emitting ruminants), soil compaction and loss, effluent (pigshit), biodiversity impacts (eg land clearing in South America), etc. Efficiency seems like a very narrow scope.
posted by wilful at 9:52 PM on September 19, 2007

I think the simple answer to this question is the domesticated animals we eat most, pork, chicken, and beef, are the most efficient to raise. There is a reason that these animals make up a majority of our diets. If there were more efficient animals out there we would be eating those every day instead.
posted by outsider at 12:47 AM on September 20, 2007 [1 favorite]

The question is ambiguous. When you say "how much energy does it take...", do you mean fossil energy? Solar energy? Units of human work? Something else?

Pasture-raised beef, lamb, or chevon (goat) would have to be the most efficient in terms of fossil energy, as there need be no input of grain (which generally takes a fair amount of fossil energy to raise and harvest, even when organic). The animal feeds itself on food that grows by itself.

Wildlife would also fit this profile, though from what I've seen of hunting, it usually involves a lot of transportation. The hunter seldom lives near the the fish or game, and so there's the expenditure of getting to the meat (you said to exclude the cost of bringing it home).

While it's true that you can grow more vegetable protein per acre on prime farmland, there are several considerations that your friend's argument overlooks. First, there is a lot of pastureland/rangeland that is totally unsuitable for raising row crops. In fact, there is far more of that kind of land than of arable land. And that land, with very little energy outlay, can be producing meat.

Second, vegetable protein is incomplete. That is, you can't simply compare total vegetable protein with total meat protein. You have to allow for the fact that one kind of vegetable protein must be supplemented with another, so it may be that it takes two units of vegetable protein to equal one of meat (just pulling those numbers out of my hat, but it illustrates the idea).

Third, there is more to nutrition than protein. Meat contains nutrients beyond those contained in the vegetative matter used to produce it, a few of which cannot be found in any vegetable source.

Fourth, where are you getting the fertility for your arable land? Yes, you can spread compost made from the harvest leavings. But you are subtracting the most nutrient-dense part of the biomass from the compost-makings every year (in the form of the corn, beans, or whatever that is sent to market). Your field will soon become barren. You can apply chemical fertilizers, which are themselves made from petroleum. Or you can let your cows into the barn at night, where they deposit some very rich fertilizer that they (not you and your tractor) have carried in from your non-tillable pastureland. There is still a net loss if you are exporting, but this is more sustainable. Add some pasture rotation into the routine and it's very sustainable.

If you really can't get sustainably raised meat in your area, then arguably you should abstain from eating meat. But humanely, sustainably raised meat is becoming more and more available.
posted by bricoleur at 5:36 AM on September 20, 2007