Sunday, June 13, 2010

How big is a chicken's footprint?

I've been thinking about chickens a lot recently.

I would dearly love to raise my own chickens for eggs and meat. But if I raise chickens, I want to do so not just humanely (which is relatively easy), but also as sustainably as possible (which is a much bigger challenge).

Total sustainability implies a closed, self-supporting system that can operate indefinitely without taking inputs from elsewhere. A closed system would, for example, provide all of the nutrients and dietary supplements (including grit) that a chicken needs in order to be healthy and productive. It would also provide all housing materials.

Modern domestic chickens are the descendents of Red and Grey Junglefowl, which evolved in the tropical forests of Asia. Generally speaking, the further removed a chicken is from its native tropical forest environment, the more dependent it will be on its human keeper for food, shelter, and protection.

The first major problem I have with creating a sustainable chicken-raising operation is that my "system" (my land) is only two acres in size. So, the first question I asked myself, before eagerly rushing out to buy some chooks, was: how much land does one productive chicken need?

I may as well have asked myself: how long is a piece of string? The answer to the chicken question depends on a large number of variables, including: what is the local climate like? (Is the land bountiful? Is it prone to drought? Is it under snow for several months of the year?). And what exactly is a "productive" chicken, anyway? (Is it one that produces an egg every day? Or is it one that simply performs some basic weed control?) The questions go on, but I'm sure you get my drift.

So, I started Googling, and (as my favourite blogger noted at the time) I found a figure that has surprised everyone I've mentioned it to: the general consensus seems to be that a 100% free range chicken requires roughly half an acre of land in order to meet all of its requirements. 

Most of the people I've mentioned this "Chicken Footprint" to have responded with incredulity; even (or perhaps especially) the people who actually raise chickens - although I'm yet to meet a chicken owner who maintains even one healthy chicken without buying supplementary feed or additives of some description.

(As an interesting side note, some local friends mentioned that the monetary value of the chicken feed they buy actually exceeds the monetary value of the eggs they get from the half-dozen aging hens in their backyard).

Lierre Keith, author of The Vegetarian Myth, touches very briefly on the chicken footprint concept in Chapter 1 of her book. She writes:
I’ve heard vegetarian activists claims that an acre of land can only support two chickens. Joel Salatin, one of the High Priests of sustainable farming and someone who actually raises chickens, puts that figure at 250 an acre. Who do you believe?
Keith heavily implies that her readers should unquestioningly believe that one acre of land can sustainably support 250 chickens. Unfortunately, she provides no data or reference to support her belief. However, if she had bothered to read Joel Salatin's own book on the subject of raising pastured poultry, she would realise that her belief is, quite simply, wrong.

As an aside, it's interesting that Lierre Keith refers repeatedly to Joel Salatin as a "high priest". Unfortunately, her belief in Salatin's ability to squeeze truly miraculous levels of productivity out of one acre of land seems faith-based rather than fact-based. Maybe Salatin should capitalize on the religious-style fervour he stirs in people, and start a new cult:

Joel Salatin, the Messiah of Meat Lovers

As it happens, I own a copy of Salatin's book, Pastured Poultry Profits. The book (which is widely regarded as the best source of information about raising chickens on pasture) was first published in 1996, and was most recently updated in 1999.

The crux of the matter is this: "chickens cannot be totally grass-fed, according to several experts. They also need grain." (Ref: Chicken Feed)

Why can chickens not be totally grass fed? Because chickens are omnivores; they are not grazing, grass-eating, specialist herbivores. By contrast, sheep, cattle, and geese are physically adapted to thrive on a diet of 100% grass.

It is no coincidence that it is primarily omnivorous farm animals - pigs and chickens - who have ended up suffering the intensive confinement of factory farming. Why? Because pigs and chickens "destructively" dig up pastures in search of highly nutritious sub-surface critters and other goodies, such as roots.    

As it happens, even Joel Salatin's "pastured" chickens are mostly grain fed. According to Salatin, "the prepared ration represents 80 percent of the [pastured] bird's diet". He goes on to explain that 92% of the prepared ration he feeds his chickens is made up of annual grains, specifically:

Corn - 52%
Soy  - 29%
Oats - 11%

"So what?", you might ask.

The point is that, based on average US yields of corn, soy, and oats, you can't actually grow enough grain on one acre to feed 250 chickens (even assuming the chickens are getting 20% of their feed from pasture). And even if you could grow enough grain on one acre, where would those 250 chickens be living while you grow the grains to feed them (keeping in mind that corn, soy, and chickens all share the same spring and summer growing period)?

Following are the assumptions I used to calculate roughly how much grain it would take to feed Salatin's 250 Cornish Cross chickens for 6 months (which is how long Salatin raises broilers for each year).

The Cornish Cross is a large, fast-growing meat breed of chicken, which, in addition to fresh pasture, eats about 150g of feed per day (reference: Washington State University). Multiplied by 250 birds, that's 37.5kg of grain per day. Multiplied by 182 days (i.e. 6 months), that comes to a total of 6.8 tonnes of grain per year.

Broken down by grain (according to Salatin's feed mix), and using average US yield data, that's:

3.5 tonnes corn @ 4130kg/acre = 0.85 acre
2.0 tonnes soy @ 1188kg/acre = 1.68 acres
0.7 tonnes oats @ 1900kg/acre = 0.37 acres

TOTAL = 2.9 acres - just to grow the necessary grain to feed 250 birds for six months.

Then there's the acre of pasture that these chickens need to actually live on, bringing us up to 3.9 acres thus far, which equates to a substantially reduced figure of 64 birds per acre. If you subtract Salatin's average broiler mortality rate of 7.5%, you're down to 59 birds (Cornish Cross chickens are susceptible to having heart attacks late in the season, so you can't realistically expect to make a proportional saving in feed).

But that's not the end of the story by a long shot.

Salatin's super-productive system relies on the highly-controlled confinement and movement of (to use Salatin's words) "race car chickens". The Cornish Cross is a hybrid chicken which is "constantly being genetically upgraded by the commercial industry to perform at a totally unnatural gain rate" (also Salatin's words, ref: p.32). 

Salatin places his broilers in moveable pens which provide a space, on average, of less than two square feet per chicken. In this respect, it's worth noting that Salatin's broiler operation meets one of just two criteria which define a CAFO (a.k.a Concentrated Animal Feeding Operation, a.k.a a factory farm). Specifically: the animals are confined for at least 45 days in a 12-month period. 

Now consider some of the inputs, other than grain, that Salatin draws on to raise his pastured poultry (the following are all specifically mentioned in Salatin's book):

* live chicks from a commercial hatchery
* wood shavings for chick bedding (Salatin's chicks live on a floor of wood shavings for 12 to 28 days of their 56-day lifespan. Salatin raises multiple batches of chickens each season).
* artificial heat source to keep chicks warm
* drinking water
* feed and water containers
* hay chaff
* moveable pens (made from treated softwood, aluminum sheeting, chicken wire, screws, etc)
* plastic buckets (as Salatin says: "the world revolves around 5 gallon buckets")
* grit (creek sand and aggregate)
* feed grade limestone
* mineral supplements
* fish meal
* kelp meal (from Iceland)
* commercial probiotic
* cattle for keeping the pasture short before and after the chickens pass through
* tractor and fuel for transporting feed, water, and chickens.

Could anyone (besides Lierre Keith) seriously claim that all of these materials can be sourced sustainably from one acre of land? With room to spare for the actual pasture-fed chickens?

Furthermore, key factors that Joel Salatin's broiler system doesn't concern itself with at all are:

* Breeding: Salatin buys his chicks from a commercial hatchery. The poultry hatchery industry is a form of factory farming whose collective harm goes way beyond the scope of this blog post.

* Incubation: Salatin's system is based on artificial incubation, and the controlled confinement of all broilers, at all times.

* Winter care for birds: Salatin only keeps broilers for six months of each year, which is convenient for him, because Polyface Farm gets deep snow over winter. Chickens evolved in tropical jungle, so they don't cope well with snow. They certainly can't be expected to utilize fresh pasture for food during snowy winters. Hence, you would have to double the amount of land, or halve the number of chickens, in order to produce enough feed to keep the birds alive for an entire year. This brings us down to fewer than 30 birds per acre, or less than 12% of the stocking rate suggested by Lierre Keith - and that's still completely ignoring all of the inputs in the list above.

Having thought long and hard about this issue, I suspect that a chicken probably needs more than half an acre, assuming that your environmental accounting is unflinchingly honest (by which I mean that all inputs, including timber, fossil fuels, metal and plastic, as well as feed supplements such as fish meal, grit, and Icelandic kelp etc, are recorded in the ledger).

So. I think I can justify keeping a few chickens, even though creating a closed chicken-raising system on my two acres remains a pastoral fantasy. But, at the very least, I'm quite convinced that a pastured chook would have a happier life than a factory chook; and happiness counts, in my ledger.


  1. This accounting of a chicken's needs goes some way to exposing the real cost of the food that we eat.

    It is really, really hard to get an accurate picture of this cost because of the specialisation of industry. No commercial egg of chicken producer grows chickens without external inputs. Chicken farms are just one step in the chicken manufacturing chain (as you point out above) that spans continents and oceans: corn and soy from broad acre farmers, rock from quarries, fish meal from the oceans.

    When you set about trying to tally all of this up people want to exclude the costs of production of many of the inputs arguing that they serve multiple purposes. All that serves to do is to downplay just how interdependent the industries that provide our most basic needs (food, water, and shelter) are.

    We need to understand the _real_ cost and requirements of producing our food.

    Thanks for an informative post.

  2. Hi Sam,
    Have you thought about geese as the poultry of choice. They may be a better bang for your buck for your situation.
    And a couple of ideas on providing extra protein for your chickens. One reasonably reliable the other maybe not so, but with a swish net and a freezer it could be a goer from time to time.
    Bio-Composting with Black Soldier Fly larvae

  3. Hi jonesy,

    I've been meaning to say thanks for that pumpkin bread recipe. I'll be sure to try it next time I crack a pumpkin open!

    Thanks also for the suggestions. I have indeed thought about geese, and the idea appeals to me - although I've read that dressing a goose is not a job for the faint hearted!

    As for black soldier fly larvae - yum yum! The idea of composting with them is new to me, and very interesting. Thanks for the links.

    Something we do have here in abundance is slaters (aka woodlice), which chickens apparently love. The only "problem" is that the slaters congregate and breed in non-pasture environments, e.g. under logs and rocks. But with a little bit of design and lateral thinking, I'm sure we could easily build some nice slater habitat into a pasture rotation system.

  4. "I've read that dressing a goose is not a job for the faint hearted!"

    To easy, get Lang to do it. :-)

  5. Wonderful! I'm so happy I found your blog (via your comment on Doomstead Diary). This discussion - as well as the more recent post on soil (I've yet to read "down" in your blog) - is what I am looking for: in-depth, critical, thoughtful and, especially, *mindful*. Consider me a devoted reader!

  6. Thanks very much for your feedback, Katrien. Much appreciated.

  7. Hi Samantha - Really interesting post, and I wanted to comment on a few issues.

    I keep 14 chickens and a rooster, plus 4 sheep, plus ourselves on an organic farm in Wingatui (just outside Dunedin), New Zealand.

    We're nowhere near max productivity yet, but are working towards completely sustaining ourselves and our stock. We're also vegetarian, eating very little dairy.

    What I already notice is the difference seasonally on how much food we import for our chooks. In summer, very little - the free range bugs, plus fallen fruit etc probably covers 80% of their diet on our property (yes, really).

    In winter, another story. We buy wheat in 40 kg bags, and go through about 1 bag every 2 months, plus a bag of layer pellets every few weeks, plus grit from outside, plus hay from outside as well (for nesting).

    We supplement the grit with crushed eggshells recycled, and we supplement the chook food and free ranging with kitchen scraps.

    I outline costs and benefits of backyard chooks in detail here Are backyard chickens profitable? A cost per egg comparison

    All up, I think we could probably sustain our chooks on our land - if we had to - for their food. But we'd still need to import grit.

    My guesstimations are that a chook clawprint is much lower than half an acre per chook, but much higher than most people would expect. Also that free ranging really lowers the clawprint, as opposed to batteries or barn chooks.

    As we move more towards sustainability (we've only been moved in 4 months!) I'll be interested to see the figures worked out more.

    Thanks for suggesting this issue be looked at more in depth. I will do so, and post my findings!

  8. Hi Daharja,

    Thanks very much for your thoughtful and interesting comment.

    I certainly accept that your chicken footprint in NZ is *much* smaller than it is here in dry old Oz. (After all, wheat yields per acre in NZ are *four times* what they are here in Australia - 3.2 tonnes per acre vs. 0.8 tonnes per acre).


    But I keep wondering why I can't find *anybody* who *actually* supports a self-replacing flock of chickens 100% on their own land?

    If it's as easy as people keep telling me it is, why does *nobody* actually do it? Why do people keep forking out hard-earned cash for feed and supplements if they don't have to? The obvious conclusion is that keeping chickens healthy and productive is actually much harder than most people are prepared to acknowledge.

    By contrast, I know a number of people who have sustainable, closed-system sheep flocks (but, as I keep repeating like a broken record: sheep are ruminant herbivores, so they thrive on healthy pasture).

    As JMG reminded his readers in the latest Archdruid Report: "talk is cheap".

    So, Daharja, if you ever actually manage to reduce your purchased chicken feed and supplements to zero, please let me know, because you'd be the first person I've ever known to achieve that!

  9. I raise four hens and one Rooster on half an acre. I only have to buy food over the winter. I get all the eggs I could want and give a bunch away. I don't try to get eggs over winter so I don't have to feed as much. My yard is full of white clover (ladino clover) and I move their 35 square foot(7x5 and 3.5 high) pen every day. The pen is mostly open, but protected roost. Also I over winter them in the fence in garden and let them spend all winter and spring scratching through the leaves I've rake up and put in the garden. So they spend all winter and early spring turning and fertilizing my garden. So I kind of think the winter feeding is doing double duty keeping the birds alive and fertilizing my garden. chicken poop and yard waste have kept my garden very productive. I do give them a little bit of oyster shell in the spring, but once they start eating insects, they don't have soft eggshell problems. I keep everything very clean and I've had very few health problems.

    If I didn't have a winter season I would be pretty darn close to completely sustainable with my five chickens.

    I don't believe it would be anywhere possible to raise 125 chickens on half an acre. Not sustainably at least.

    Good read thanks.


  10. You can get slaters etc for your chickens by leaving timber boards lying on the ground. Call the chickens over and turn over a board, and they'll go nuts for everything underneath!

    Leave each board down for a few days or a week before turning - but with lots of boards, you should be able to turn a few each day.

    It's not going to be a major food source, but it will be a nice protein treat!

  11. Sorry, I've been thinking about this some more over the weekend. Once I get a thought in my head, it stays there until I can think it through!

    According to John Jeavons and the practitioners of biointensive gardening, you can grow enough food for one person sustainably on 4000 ft2 of actual garden beds. That's about 400 m2 (roughly).

    Now, assuming a chicken eats much less than a person, and we can eat pretty much the same foods, then it would seem that an acre (4000 m2) should be able to support 10 chickens easily, probably several times that number.

    Presumably, if you were growing specifically for chickens you could grow stuff like mangelwurzels and comfrey that give a higher yield, rather than sticking just to food people enjoy eating.

    The biointensive approach does aim for proper sustainability - the growing area they quote includes the space required to grow enough "waste" biomass to feed your compost heaps to supply enough fertility to the garden beds to continue growing indefinitely.

    I don't think it's that simple, obviously. Growing food this way would be very labour-intensive. Plus you'd need to carve out some space for paths, compost bays, chook pens, etc.

    But I think it shows that if you depart from the traditional approach (feeding chickens on corn/soy/oats), you should be able to sustain many more chickens per acre.

    It's just a thought experiment, but it's got me thinking more about what I can grow to supplement my flock's diet and reduce the feed bill!

  12. Hi Darren. Thanks for your comments. I'm really pleased that you found this post thought provoking. I've certainly found your comments thought-provoking.

    I'm an admirer of John Jeavons, so I'm inclined to accept the numbers you provide above for food and soil replenishment.

    But, I still doubt that it's possible to provide the total nutrient, shelter, water, and breeding requirements for 10+ chickens from one acre of land - it's certainly difficult enough that nobody I know, or know of, comes within cooee of actually achieving that.

    One important issue: I barely touched on the subject of replacement chickens in my post, but it's a crucial factor that no one I know of concerns themselves with in a truly serious and sustainable way. I have had a number of neighbours who intended to be self-sufficient chicken breeders, but *something* inevitably seems to go catastrophically wrong - for example, inbreeding depression can become problematic after a few generations if you're not importing fresh genetic stock - this typically results in birds with low vigour that tend to be unproductive. Then there's the harm wrought by foxes, dogs, birds of prey, etc. Most people shrug off these losses ... which is easy to do when you can just drive somewhere and buy replacements.

    Most of the backyard chicken enthusiasts I know simply purchase a handful of young isa browns or australorps when their existing chooks become uneconomical to maintain. Commercial egg and broiler producers certainly don't produce their own chicks on site. I had actually meant to write a separate post about the hatchery industry, which is absolutely soulless - I reckon that the proprietary breeding process for isa browns would turn a lot of greenies off that breed. But that's a big issue for another time!

    Anyway, I'm *very* interested in your thoughts and experiments with chicken feed, and I'm looking forward to following your future progress on your blog.

  13. Very interesting post. Gave me plenty to think about. However, I just wanted to point out that your calculations are a bit off.

    When you estimated the amount of grain required to feed 250 chickens, you calculated based on feeding each chicken for six months. If you read Salatin's book more closely, you will find that, while he raises meat birds for six months of the year because that is all the climate in Virginia allows, each meat bird is slaughtered at around two months. That would change your math significantly.

    I agree that some of the inputs for these birds (kelp? limestone? etc) raise some questions, others are dealt with quite simply. For instance, Salatin doesn't build new pens for each group of chickens. Each chicken tractor he builds is used for years and probably houses over a thousand birds. The tractors themselves can be built from scrap materials. Five gallon buckets can be found lying around for the taking by any thrifty individual. Adding these materials into your calculations seriously misrepresents the reality of raising chickens.

  14. Hi Ravi, and thanks for your comments, although it seems that you didn't read my post very carefully. For instance, I specifically mention the fact that Salatin's broilers only have a "56-day lifespan" - but that's irrelevant to the question I was addressing, which is: how many chickens can live *truly sustainably* on a given area of land at any one time.

    Furthermore, your assertion that "buckets can be found lying around for the taking by any thrifty individual" is based on some big assumptions. Buckets eventually break, and the petrochemical and plastics industries run on a strictly finite resource, namely oil. Therefore, a farm that is dependent on plastics, synthetic fertilisers, and any number of other petroleum-based resources is not sustainable in the long term. I'm thinking about the *future*, not just about what's available this week, or even perhaps this lifetime.

  15. Samantha,
    I saw that you did acknowledge the 56 day lifespan in your list of inputs, but what I am referring to is the math you used to arrive at your figure of 6.8 tonnes of grain to raise 250 meat birds.

    Correct me if I am wrong, but you arrived at that figure by using the following math:

    250 chickens x 150 g of grain/day = 37.5 kg of grain/day
    37.5 kg x 182 days = 6.8 tonnes

    If you were raising 250 Cornish Cross chickens, they might eat 37.5 kg of grain/day, but you wouldn’t be feeding them all for 182 days because they are only raise for 56 days.

    If that is true, I believe the numbers should look something like this:

    250 chickens x 150g of feed/day = 37.5 kg of feed/day
    37.5 kg x 56 days = 2.1 tonnes

    Please let me know if I am missing something here.

    Also, I agree that a sustainable farm should not be reliant on plastics, etc. I would argue that Salatin’s model is not dependent on these materials. He uses plastic buckets because we live in a society that uses these materials and throws them away, so they are there for the taking. If we didn’t live in a society that used plastic buckets and then left them by the dumpster, his model would not fall apart, he would simply come up with something different to use as his chicken waterers.

    Of course it would be better for everyone if there were not an abundance of 5 gallon plastic buckets being produced and then thrown away. Salatin’s model does not create the demand for those buckets; rather, it salvages waste products from other unsustainable industries and finds ways to make them useful until they are so brittle they can no longer be used as waterers. At that point in time, innovative farmers could find another use for the plastic. At worst, even if the plastic ends up in a landfill at that point, it is with the knowledge that that is where they were headed before they were rescued to be used for a decade as chicken waterers.

    When the world stops producing plastic/petrochemical waste products and there are no more five gallon buckets filling up dumpsters, then it makes sense to figure out how to construct a waterer out of natural materials that is built sustainably. Until that point in time, however, dedicating natural resources to build livestock waterers seems like a wasteful philosophical exercise when one could simply take a trip to the dump and find plenty of items that could be used as waterers, etc. on the farm.

  16. Hi Ravi. The point you're missing is that *my* model for *my* land is not about churning out dead chickens every 8 weeks! As I said in my 1st paragraph, I want to raise chickens for eggs and meat - but if I kill all of my birds 8 weeks after purchasing them, I'd obviously end up with none.

    I used Salatin's "pastured poultry" model for 2 reasons: 1) because I happened to have his book on my shelf, and 2) because people like Lierre Keith have flippantly used Salatin's model to "prove" that an acre of land can sustainably support 250 chickens. Not "meat chickens" just "chickens".

    And now we arrive at the second broad point in my post that you seem determined to ignore, which is that new chickens have to come from somewhere, and Salatin gets his from a commercial hatchery. If you think the modern commercial hatchery industry is sustainable in the long term, then I suspect you have no idea how it operates. And if you think that all modern hatcheries could simply be replaced with sustainable versions when we run out of cheap oil, then you don't understand the fundamentals of our growth-based, oil-dependent economy.

  17. We're in complete agreement about commercial hatcheries. There's nothing sustainable at all about them. And without commercial hatcheries, the Cornish Cross would no longer exist, considering they cannot even breed on their own.

    Thanks for your replies. I just discovered your blog a few days ago, and I'm enjoying it quite a bit!

  18. Hi Sam, I just found your blog. Thanks for calculations!

    Just wanted to mention something, since you asked about people who hatch their own chicks. My brother in law has a small "farm" on about six acres, in Virginia, a little west of Polyface Farms. (Maybe 100 miles? I am not quite sure where they are, exactly.)

    He breeds and raises his own chickens, mostly for eggs. I think he does something like 2-4 hatchings per year. He has something on the order of 50 chicken, limited by tiem to deal with them rather than amound of land. He uses movable chicken coops similar but smaller than Salatin's, but he does feed them with commercial (organic) chicken feed. I would venture to guess that the reason most people do, is because it is easier to specialize in either chickens OR grain. (also, I know there are additives like calcium, no idea where to get that)

    If you are interested in some more data on what he does, I could find out, but I bet that there are people in your area that do similar things.

    Thanks for putting so much thought into this!