let's talk farm animals

Least Harm Principle suggests humans should eat beef, lamb, dairy, not a vegan diet.

By S.L. Davis, Department of Animal Sciences, Oregon State University, Corvallis, OR 97331.
Published in the Proceedings of the Third Congress of the European Society for Agricultural and Food Ethics, 2001, pp 440-450.


Although the debate over the moral status of animals has been going on for thousands of years (Shapiro, 2000), there has been a resurgence of interest in this issue in the last quarter of the 20th century. One of the landmark philosophical works of this period was the book by Regan (1983) called “A Case for Animal Rights.”

In that book, Regan concludes that animals do have moral standing, that they are subjects-of-a-life with interests that deserve equal consideration to the same interests in humans, and therefore have the right to live their lives without human interference. As a consequence, he concludes that humans have a moral obligation to consume a vegan (use no animal products) diet and eliminate animal agriculture.

However, production of an all vegan diet also comes at the cost of the lives of many animals, including mice, moles, gophers, pheasants, etc. Therefore, I asked Regan, “What is the morally relevant difference between killing a field mouse (or other animal of the field) so that humans may eat and killing a pig (or chicken, calf or lamb) for the same purpose? Animals must die so that humans may eat, regardless whether they eat a vegan diet or not. So, how are we to choose our food supply in a morally responsible manner?”

Regan’s response could be summarized by what may be called the “Least Harm Principle” or LHP (Regan, Personal Communication). According to LHP, we must choose the food products that, overall, cause the least harm to the least number of animals. The following analysis is an attempt to try to determine what humans should eat if we apply that principle.

Regan’s Vegan Conclusion is Problematic

I find Regan’s response to my question to be problematic for two reasons. The first reason is because it seems to be a philosophical slight of hand for one to turn to a utilitarian defense (LHP) of a challenge to his vegan conclusion which is based on animal rights theory. If the question, “What is the morally relevant difference?” can’t be supported by the animal rights theory, then it seems to me that the animal rights theory must be rejected. Instead, Regan turns to utilitarian theory (which examines consequences of one’s actions) to defend the vegan conclusion.

The second problem I see with his vegan conclusion is that he claims that the least harm would be done to animals if animal agriculture was eliminated. It may certainly be true that fewer animals may be killed if animal agriculture was eliminated, but could the LHP also lead to other alternative conclusions?

Would pasture-based animal agriculture cause least harm?

Animals of the field are killed by several factors, including:

1. Tractors and farm implements run over them.

2. Plows and cultivators destroy underground burrows and kill animals.

3. Removal of the crops (harvest) removes ground cover allowing animals on the surface to be killed by predators.

4. Application of pesticides.

So, every time the tractor goes through the field to plow, disc, cultivate, apply fertilizer and/or pesticide, harvest, etc., animals are killed. And, intensive agriculture such as corn and soybeans (products central to a vegan diet) kills far more animals of the field than would extensive agriculture like forage production, particularly if the forage was harvested by ruminant animals instead of machines. So perhaps fewer animals would be killed by producing beef, lamb, and dairy products for humans to eat instead of the vegan diet envisioned by Regan.

Accurate numbers of mortality aren’t available, but Tew and Macdonald (1993) reported that wood mouse population density in cereal fields dropped from 25/ha preharvest to less than 5/ha postharvest. This decrease was attributed to migration out of the field and to mortality. Therefore, it may be reasonable to estimate mortality of 10 animals/ha in conventional corn and soybean production.

There are 120 million ha of harvested cropland in the US (USDA, 2000). If all of that land was used to produce a plant-based diet, and if 10 animals of the field are killed per ha per year, then 10 x 120 million = 1200 million or 1.2 billion would be killed to produce a vegan diet.

If half of that land (60 million) was converted to forage production and if forage production systems decreased the number of animals of the field killed per year by 50% (5 per year per ha), the number of animals killed would be:

1. 60 million ha of traditional agriculture x 10 animals per ha = 0.6 billion animals killed.

2. 60 million ha of forage production x 5 animals of the field = 0.3 billion.

Therefore, in this hypothetical example, the change to include some forage-based animal agriculture would result in the loss of only 0.9 billion animals of the field instead of 1.2 billion to support a vegan diet. As a result, the LHP would suggest that we are morally obligated to consume a diet of ruminant products, not a vegan diet, because it would result in the death offewer animals of the field.

But what of the ruminant animals that would need to die to feed people?

According to the USDA numbers quoted by Francione (2000), of the 8.4 billion animals killed each year for food in the US, 8 billion of those are poultry and only 41 million are ruminants (cows, calves, sheep, lambs). Even if the numbers of ruminants killed for food each year doubled to replace the 8 billion poultry, the total number of animals that would need to be killed under this alternative would still be fewer (0.9 billion + 82 million = 0.982 billion) than in the vegan alternative (1.2 billion).

In conclusion, applying the Least Harm Principle as proposed by Regan would actually argue that we are morally obligated to move to a ruminant-based diet rather than a vegan diet.


Davis, S.L. 2000. What is the Morally Relevant Difference between the Mouse and the Pig? Pp. 107-109 in the Proceedings of EurSafe 2000; 2nd Congress of the European Society for Agricultural and Food Ethics.

Francione, Gary L. 2000. Introduction to Animal Rights: Your child or the dog? Temple UniversityPress. Philadelphia.

Regan, Tom. 1983. A Case for Animal Rights. University of California Press, Berkeley.

Shapiro, L.S. 2000. Applied Animal Ethics, pp. 34-37. Delmar Press.

Tew, T.E. and D.W. Macdonald. 1993. The effects of harvest on arable wood mice. Biological Conservation 65:279-283.

USDA. 2000.


Posted by FFC on July 13th, 2009 :: Filed under Consumers,Education and public awareness,Vegan
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10 Responses to “Least Harm Principle suggests humans should eat beef, lamb, dairy, not a vegan diet.”

  1. Quora
    January 25th, 2011

    What is an intelligent argument and/or reason for not becoming a vegetarian?…

    Being a vegetarian is bad for your body, it is unsustainable, and it kills more animals in the process of farming than it saves by avoiding the consumption of meat. Sustainability: Wild or pastured meat is the only sustainable food source. In order to …

  2. Quora
    January 25th, 2011

    Is vegetarianism good for the environment?…

    Vegetarianism is better for the environment than eating meat that is fed grains. However, both are unsustainable. Humans cannot survive on vegetables alone, which is why we need grains and legumes to get all of the necessary amino acids on a vegetarian…

  3. Rib Eye
    January 28th, 2011

    This article is dumb. I said it. Yup, completely absurd. Total twisted logic and BS with so much left out of the whole picture. I just have to say once again, this article is dumb.

  4. Jesse
    May 4th, 2011

    Or we could just go back to community farms plowed by hand. I mean, if we’re going to take the position of radically changing the massive food production system, why not just get away from the massive side?

    I believe some calculations say that a family of 4 could grow all the food they need on less than .2 acres of land. Breaking it apart so everyone can manage their own food incomes in a way that does pollute as heavily (tractors and other farm equipment) seems more in keeping with LHP than Dr. Davis’ suggestion.

  5. David
    June 22nd, 2011

    “And, intensive agriculture such as corn and soybeans (products central to a vegan diet) kills far more animals of the field than would extensive agriculture like forage production, particularly if the forage was harvested by ruminant animals instead of machines. So perhaps fewer animals would be killed by producing beef, lamb, and dairy products for humans to eat instead of the vegan diet envisioned by Regan.”

    This is fallacious reasoning. Intensive agriculture of corn and soybeans are also central products to a cow’s or a sheep’s diet… so much so that more than 75% of soy, corn and other major cereal are fed not to vegans, or even people in general, but to farm animals like cows, pigs, chickens and sheep.

    People who don’t eat animals are responsible for less soy and corn since they’re consuming nutrients from these foods directly and not through an animal who used a lot of the calories of these foods for his own purposes. Even if every person in the world became vegan, its hard to imagine we’d consume as much more soy and corn as it takes to feed the 60 billion land animals we raise for food each year.

    This is not to mention that the suffering and exploitation of farm animals is qualitatively worse than that of field animals on an order of magnitude that’s obvious to anyone familiar with common factory farming practices.

  6. Craig
    August 23rd, 2011

    Did no one notice this? .4 billion is actually 400 million. That entire last paragraph is completely ignorant to simple math. Not counting all other ignorance’s, oversights and just plain jibber-jabber, this article is useless.

  7. Jan
    September 8th, 2011

    how do you suppose we sustain a 6 billion people population if we all ate field crops? without animals?

  8. [...] yet PETA and other animal rights organizations never speak out about these animals. Why not? Yet further, the Least Harm Principle suggests that eating beef is – wait for it – causing the least… So which is the more [...]

  9. mijnheer
    February 22nd, 2013

    Steven Davis raises the interesting question of the number of animals killed during crop production. However, he badly misrepresents Tom Regan’s position. Regan never adopts a utilitarian position. In The Case for Animal Rights, beginning on p. 302, Regan devotes considerable space to explaining why he rejects what he calls the “minimize harm principle” (i.e., the utilitarian position that Davis attributes to him under the name “Least Harm Principle”).

    On another website, Davis quotes Regan as saying “Whenever we find ourselves in a situation where all the options at hand will produce some harm to those who are innocent, we must choose that option that will result in the least total sum of harm.” Regan does indeed write these words in his book, but he does so in order to describe the utilitarian position that he firmly rejects!

    Readers should be aware that Davis’s calculation of animal deaths has been challenged by more than one writer. See here: http://www.animalvisuals.org/projects/data/1mc/

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