Cow Versus Chicken: The True Carbon ‘Hoofprint’ of Livestock

We know that raising farm animals as part of the food production system contributes markedly to green house gas emissions, also known as a ‘carbon hoofprint.’ But is there a difference between the impact on climate between different countries? Which animals are leaving the greatest mark on our environment and climate?

The newest paper to be published in the Proceedings of the National Academy of Sciences (PNAS) investigates the answers, providing a comprehensive assessment of what cows, sheep, pigs, poultry and other farm animals are eating in different parts of the world. The study also analysed how efficiently they convert that feed into milk, eggs and meat, and the amount of greenhouse gases they produce.
Scientists say the new data fill a critical gap in research on the interactions between livestock and natural resources region by region.

“This very important research should provide a new foundation for addressing the sustainable development of livestock in a very resource-challenged and hungry world, where, in many areas, livestock can be crucial to food security,” said Harvard University’s William C. Clark, editorial board member of the Sustainability Science section at PNAS.

Poor Versus Wealthy

The study found a significant increase in the amount of food needed to produce one kilogram of protein for animals in the developing world as opposed to animals in wealthy countries.

To do so, the researchers broke down livestock production into nine global regions—the more developed regions of Europe and Russia, North America and Oceania, along with the developing regions of Southeast Asia, Eastern Asia (including China), South Asia, Latin America and the Caribbean, sub-Saharan Africa, and the Middle East and North Africa.

It was found that in arid regions of sub-Saharan Africa, for example, the food available to grazing animals contained far fewer nutrients than that in other regions. Therefore, cows were consuming up to ten times more feed—mainly in the form of rangeland grasses—to produce one kilogram of protein than a cow kept in more favorable conditions.

Subsequently, the developing world were found to account for the most emissions from livestock, including 75 percent of emissions from cattle and other ruminants and 56 percent from poultry and pigs. However, we have to interpret these findings with caution as the numbers do not include emissions from the food production system as a whole, but rather just the animal.

“While our measurements may make a certain type of livestock production appear inefficient, that production system may be the most environmentally sustainable, as well as the most equitable way of using that particular land,” said Philip Thornton, co-author of the study.

Emission Intensity

The amount of greenhouse gases released for every kilogram of protein produced is known as “emission intensity.” In this study, scientists modelled only the emissions linked directly to animals—the gases released through their digestion and manure production. Naturally, gas emissions vary widely depending on the animal involved and the quality of its diet.

Cattle (for beef or dairy) are the largest contributors of greenhouse emissions from livestock worldwide, accounting for a whopping 77 percent of the total. Pork and poultry (monogastrics) account for just 10 percent of emissions.

The authors speculate that the driver behind the low emissions of the monogastrics industries are the large industrial systems in place. These systems have additional carbon costs not factored into the numbers above — notably greenhouse gases produced by the energy and transport services, as well as the felling of forests to grow crops for animal feed. The industrial system used by the cattle industry seems to be overlooked.

Feed Efficiency

For scientists, the most important insights emerging from the new data relate to the amount of feed livestock eat to produce per one kilogram of protein, known as “feed efficiency.”

The study shows that ruminant animals (cows, sheep and goats) require up to five times more feed to produce one kilogram of protein in the form of meat than one kilogram of protein in the form of milk.

“The large differences in efficiencies in the production of different livestock foods warrant considerable attention,” the authors note. “Knowing these differences can help us define sustainable and culturally appropriate levels of consumption of milk, meat and eggs.”

Cow Versus Chicken

Comparing carbon costs of livestock globally, poultry produced 3.7 kilograms of carbon per kilogram of protein, and pork produced 24 kilograms of carbon per kilogram of protein. Now compare this to ruminants, which produced anywhere from 58 to 1,000 kilograms of carbon per kilogram of protein.

The study confirmed that pigs and poultry are far more efficient at converting feed into protein than are cattle, sheep and goats, and this is the case regardless of which country the animals are raised.

Considering the carbon hoofprint of different animals, as well as the amount of land and resources required to produce an animal’s feed, it’s become very clear which livestock are favourable in terms of sustainability.

Photo credit: Thinkstock


Jim Ven
Jim V11 months ago

thanks for the article.

Carrie-Anne Brown

thanks for sharing :)

Panchali Yapa
Panchali Yapa3 years ago

Thank you

Gerald L.
Gerald L3 years ago

Turkey Thoughts; for those with acreage who want to raise birds with negligible feed inputs, turkey chicks are #1 with my experience they did not even finish their bag of starter feed. They were free range, foraging for bugs, grubs and grasses. They had no use for their house, sleeping high up in hardwood trees. And quite sociable, not nasty like geese. Missed a picture once of the 12 of them sitting on the seats and seat backs of a double glider swing. Would still be collecting royalties of that missed picture for Farm Store calendars.

Had them weigh out as high as 27 lbs. in one season. Never lost any to predators, caution do not use sawdust for bedding when chicks, they did not differentiate from food. For smaller households birds this size could be portioned out and frozen, one or 2 birds would be more than enough for a years supply of meals and soup stock.

Melania Padilla
Melania Padilla3 years ago


Mark Donner
Mark Donner3 years ago

Dale O. When the overpopulated human virus is extinct (which is a 100% certainty since the psychotic virus called human is hellbent on just that goal) they will definitely stop their greedy bloodthirsty consumption of "meat". humanity in general give nothing to the environment but destruction and cruelty, so why do you think they have a right to exist at all? And its not "eons" they've been here they are a recently introduced monstrosity.. dangerously destructive, useless humanity has been here only a blink in geological time

Janis K.
Janis K3 years ago

Thanks for sharing!

Fred Hoekstra
Fred Hoekstra3 years ago

Thank you Joe, for Sharing this!

Gerald Landry
Gerald L3 years ago

@ Miles F. Spin it how you may, meat is not environmentally friendly.

sunshine = grass = ruminants = milk = cheese = butter = meat = eggs = leather = natural fibres = glue = bones = soup stock = manure = better soil = less grassland fires = less smoke pollution

But plastic shoes, soya beans, synthetic fabrics, chemical based glues, = oil wells = pollution of air, water, land from oil tankers, spills, pipelines, chemical & oil refineries, steel mills for industrial infrastructure to produce the above, sick people from chemical fumes, air pollution.

Our problem is CAFO's, feedlots etc. man existed 6000 years before feedlots in the last 60. Small farms, local production eliminate food-miles, shipping apples or lamb from New Zealand to England while their orchard apples fall to the ground shows an enormous waste of polluting carbon, steel ships, lost local lively-hood etc. Apple fed pork is delicious!

Dale O.

Karmen K proclaims: "If there's one change I want to see in this world - No more slaughterhouses!! If you like to eat meat, go ahead and kill it yourself."

Fascinating, but if one eats no meat does one have to go out and grow your own veggies, fruits and legumes organically all by oneself if one has no access to gardens of one's own?

People have been eating meat for eons, that will not change. One can avoid factory farm meat but one will never see a world where meat is never eaten. Or do you propose we all go deer hunting or live on hobby farms and raise our own livestock?