The Impact of Corn-Based Diets on Cattle: A Health and Ethical Issue | Exams Ethics

Eukaryon, Vol. 8, March 2012, Lake Forest College Review Article

A Difficult Reality to Digest: The Effects of a Corn-Based Diet on the

Digestive System of Cattle

Robin Graber*

Department of Biology and Environmental Studies Program

Lake Forest College

Abstract

A complex system of economic and political policies

has led to the mass over production of corn in the

United States. As a result of this overproduction, we

now see corn in the majority of processed foods as well

as animal feeds, in particular cattle feed. However,

evolutionarily cattle are adapted to pasture diets not

corn-based diets. Cattle have complex digestive

systems, consisting of the rumen, the reticulum, the

omasum, and the abom asums, which allow them to

digest cellulose and hemicellulose found in grass

blades. The addition of corn to the diet of a steer

changes the chemistry of its digestive system and leads

to serious illnesses, including bloat and acidosis. This

illness, which is extremely painful for cattle, brings into

question the ethics of feeding cattle a corn-based diet

and the ethics of the policies surrounding corn

production.

Introduction

Over the past century, Americans have become increasingly

alienated from their food. Although I have always been

somewhat aware of this ignorance, I was shocked when I

heard the story of a child who thought the word “chicken”

referred exclusively to food. This smart kindergartener did

not realize his chicken nuggets contained animal products.

In recent years, people have begun to speak out on the state

of our food system and agricultural practices, mainly due to

health and environmental concerns, with a number of people

also protesting in the name of animal rights. Popular books,

such as Michael Pollan’s The Omnivore’s Dilemma and In

Defense of Food, as well as, documentaries such as Food

Inc., King Corn, and Super Size Me, have begun to expose

the horrors o f America’s eating habits and agricultural

practices and the consequence they have for human health.

One modern agricultural practice that has become

common in developed nations, especially the United States,

is the production of monocultures, mass production of a

single crop. Monocultures cause a wide expanse of complex

environmental, health, and economic problems. In the United

States the three most common monoculture crops are corn,

soybeans, and wheat. Of these three, corn is most

commonly villainized, and for good reasons. A complex

system, of economics and subsidies has led to the mass-

over production of corn in the US. This has led to the use of

corn in processed foods an d as a common component in

animal feeds, in particular cattle feed. The idea that

America’s diet is unhealthily rich in corn is fairly common;

however, among the general public it seems that little

thought is given to the effect this corn has on welfare of an

individual steer raised for our meat consumption.

It is easiest to feed cattle grains, including corn,

because as Michael Pollan points out, in his book The

Omnivore’s Dilemma, feeding such a large number of

________________________________________________

* This author wrote the paper for Environmental Studies 289: Biodiversity and

Agriculture taught by Dr. Glen Adelson

animals in one place on corn is cheap. Consequently, meat

has become affordable for the average American household,

which has subsequently increased the demand for meat and

the amount of beef produced in feedlots. Contrary to their

feedlot corn diets, cattle evolved as g razers, and th us their

natural diet consists of a mixture of perennial grasses

(Britton). In addition to the cramped and unsanitary living

conditions of a feedlot, an individual steer must also deal

with the digestive problems associated with eating an

unnatural, grain-concentrated, diet.

Grain-rich diets have severe negative effects on

the well-being of the individual steer. The rumen enables

cattle to take advantage of fibrous grasses that contains

cellulose and hemicelluloses. The steer’s rumen evolved as

a result of the competitive advantage it provided for the

ancestors of the steer. Thus, the addition of grain, primarily

corn, into the steer’s diet directly causes digestive problems

including, but not limited to, bloat and acidosis. The following

paragraphs introduce the mechanisms of the digestive

system of a steer, and explain how problems m ay arise with

the introduction of corn into the steer’s diet.

Introduction to the Digestive System of Cattle:

Cattle evolved as grazers and thus are adapted to eating

highly fibrous foodstuffs. Consider for a moment the

limitations of a human diet. Humans are omnivores and can

eat and digest almost anything, except highly fibrous plant

material such as grass blades. Like humans, most animals

cannot digest these fibrous plant materials because they are

unable to digest the cellulose and hemicelluloses found in

the plant cell wall. For the anc estors of cattle, the

development of a m ethod enabling the digestion of these

foodstuffs was evolutionarily advantageous because there

was little competition for this abundant fibrous plant material.

During this evolutionary process, those individuals that were

able to digest fibrous plant materials survived and passed

this altered method of digestion onto their offspring. Through

this evolutionary process cattle evolved with the

mechanisms to eat and digest grasses (Britton).

Cattle belong to a category of mammals known as

ruminants. In contrast to the single stomach of monogastric

animals, such as humans, the stomach of a ruminant is

divided into four compartments: the rumen, the reticulum, the

omasum, and the abomasum; these organs comprise

approximately three-fourths of a steer’s abdominal cavity

(Bowen, 2006). In addition to this unique and complex

stomach system, ruminants are hom e to a diverse flora of

microorganisms. The presence of these microorganisms

aids in the digestion of fibrous plant materials, which contain

cellulose and hemicellulose. Cattle share what is called a

mutually beneficial, or mutualistic, relationship with these gut

microorganisms. By ingesting foodstuffs, the steer provides

the food material necessary for the microbes to produce their

own simple nutrients, which enables them to survive and

reproduce. These microbes then undergo a process know n

as rumen fermentation, which in addition to producing their

own required cellular energy, produce waste products, such

as volatile fatty acids and B vitamins, which are of no use to

the microbes, but provide the steer with essential nutrients

(Bowen 2006, Herd). Some of these microorganisms then

pass through the digestive tract and provide the steer with

additional proteins (Herd). Understanding the physiological

and molecular processes that occur in each stage of a

steer’s digestion will provide us with insight into the problems

that occur when a steer is fed a high corn diet.

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A Difficult Reality to Digest: The Effects of a Corn-Based Diet on the

Digestive System of Cattle

Robin Graber* Department of Biology and Environmental Studies Program Lake Forest College Abstract A complex system of economic and political policies has led to the mass over production of corn in the United States. As a result of this overproduction, we now see corn in the majority of processed foods as well as animal feeds, in particular cattle feed. However, evolutionarily cattle are adapted to pasture diets not corn-based diets. Cattle have complex digestive systems, consisting of the rumen, the reticulum, the omasum, and the abomasums, which allow them to digest cellulose and hemicellulose found in grass blades. The addition of corn to the diet of a steer changes the chemistry of its digestive system and leads to serious illnesses, including bloat and acidosis. This illness, which is extremely painful for cattle, brings into question the ethics of feeding cattle a corn-based diet and the ethics of the policies surrounding corn production. Introduction Over the past century, Americans have become increasingly alienated from their food. Although I have always been somewhat aware of this ignorance, I was shocked when I heard the story of a child who thought the word “chicken” referred exclusively to food. This smart kindergartener did not realize his chicken nuggets contained animal products. In recent years, people have begun to speak out on the state of our food system and agricultural practices, mainly due to health and environmental concerns, with a number of people also protesting in the name of animal rights. Popular books, such as Michael Pollan’s The Omnivore’s Dilemma and In Defense of Food, as well as, documentaries such as Food Inc., King Corn, and Super Size Me, have begun to expose the horrors of America’s eating habits and agricultural practices and the consequence they have for human health. One modern agricultural practice that has become common in developed nations, especially the United States, is the production of monocultures, mass production of a single crop. Monocultures cause a wide expanse of complex environmental, health, and economic problems. In the United States the three most common monoculture crops are corn, soybeans, and wheat. Of these three, corn is most commonly villainized, and for good reasons. A complex system, of economics and subsidies has led to the mass- over production of corn in the US. This has led to the use of corn in processed foods and as a common component in animal feeds, in particular cattle feed. The idea that America’s diet is unhealthily rich in corn is fairly common; however, among the general public it seems that little thought is given to the effect this corn has on welfare of an individual steer raised for our meat consumption. It is easiest to feed cattle grains, including corn, because as Michael Pollan points out, in his book The Omnivore’s Dilemma, feeding such a large number of

This author wrote the paper for Environmental Studies 289: Biodiversity and Agriculture taught by Dr. Glen Adelson animals in one place on corn is cheap. Consequently, meat has become affordable for the average American household, which has subsequently increased the demand for meat and the amount of beef produced in feedlots. Contrary to their feedlot corn diets, cattle evolved as grazers, and thus their natural diet consists of a mixture of perennial grasses (Britton). In addition to the cramped and unsanitary living conditions of a feedlot, an individual steer must also deal with the digestive problems associated with eating an unnatural, grain-concentrated, diet. Grain-rich diets have severe negative effects on the well-being of the individual steer. The rumen enables cattle to take advantage of fibrous grasses that contains cellulose and hemicelluloses. The steer’s rumen evolved as a result of the competitive advantage it provided for the ancestors of the steer. Thus, the addition of grain, primarily corn, into the steer’s diet directly causes digestive problems including, but not limited to, bloat and acidosis. The following paragraphs introduce the mechanisms of the digestive system of a steer, and explain how problems may arise with the introduction of corn into the steer’s diet. Introduction to the Digestive System of Cattle: Cattle evolved as grazers and thus are adapted to eating highly fibrous foodstuffs. Consider for a moment the limitations of a human diet. Humans are omnivores and can eat and digest almost anything, except highly fibrous plant material such as grass blades. Like humans, most animals cannot digest these fibrous plant materials because they are unable to digest the cellulose and hemicelluloses found in the plant cell wall. For the ancestors of cattle, the development of a method enabling the digestion of these foodstuffs was evolutionarily advantageous because there was little competition for this abundant fibrous plant material. During this evolutionary process, those individuals that were able to digest fibrous plant materials survived and passed this altered method of digestion onto their offspring. Through this evolutionary process cattle evolved with the mechanisms to eat and digest grasses (Britton). Cattle belong to a category of mammals known as ruminants. In contrast to the single stomach of monogastric animals, such as humans, the stomach of a ruminant is divided into four compartments: the rumen, the reticulum, the omasum, and the abomasum; these organs comprise approximately three-fourths of a steer’s abdominal cavity (Bowen, 2006). In addition to this unique and complex stomach system, ruminants are home to a diverse flora of microorganisms. The presence of these microorganisms aids in the digestion of fibrous plant materials, which contain cellulose and hemicellulose. Cattle share what is called a mutually beneficial, or mutualistic, relationship with these gut microorganisms. By ingesting foodstuffs, the steer provides the food material necessary for the microbes to produce their own simple nutrients, which enables them to survive and reproduce. These microbes then undergo a process known as rumen fermentation, which in addition to producing their own required cellular energy, produce waste products, such as volatile fatty acids and B vitamins, which are of no use to the microbes, but provide the steer with essential nutrients (Bowen 2006, Herd). Some of these microorganisms then pass through the digestive tract and provide the steer with additional proteins (Herd). Understanding the physiological and molecular processes that occur in each stage of a steer’s digestion will provide us with insight into the problems that occur when a steer is fed a high corn diet.

In the Rumen Physical Components of Digestion When a steer eats, large quantities of saliva along with the feed and water ingested flow through the esophagus and into the rumen. This saliva is rich in bicarbonate and thus very alkaline, or basic, meaning it has a pH above 7 (Bowen, 2006). This plethora of saliva performs two main functions. First, it maintains the fluid level in the rumen, which is necessary for fermentation to occur. Second, it acts as an alkaline buffer to neutralize the large amount of acid produced during rumen fermentation (Bowen, 2006). This is necessary to maintain the pH of the rumen within the range 5.5 - 7.0, which is required for the fermentation process (Herd). After a steer masticates, or chews, the particles flow down the esophagus and into the rumen. This food material, or digesta, can flow freely between the rumen and the reticulum and thus they are often referred to singularly as the rumen-reticulum (Herd). The rumen-reticulum complex contains approximately half of the digest systems capacity, as well as, the majority of the microbial activity (Herd). Upon primary mastication, ruminants do not break up their food well enough for effective microbial fermentation to commence, and thus perform rumination, or what is commonly known as “chewing cud” (Bowen, 2006). Rumination is the regurgitation, re-mastication, and re- swallowing of food particles (Bowen, 2006). This process increases the surface area of the food for microbial fermentation, which makes it a more efficient process (Bowen, 2006). Rumination is a physical process, in contrast to the chemical process of fermentation (which will be discussed in detail later) that aids in a steer’s digestion. Another such physical process is rumen motility. The rumen is not a static organ; it undergoes contractions every 1 - 3 minutes (Bowen, 2006). These contractions serve to mix the contents of the rumen, which increase the contact between microorganisms and foodstuffs, aid in eructation, or “belching” of gases produced during fermentations, and moves fluids and fermentation products into the omasum (Bowen, 2006). Fermentation Overview Fermentation is a process by which organic molecules are broken down without oxygen. It often occurs in the absence of oxygen, under what are known as anaerobic conditions. However, in some organisms, such as yeast, fermentation is the primary source of metabolism even under aerobic conditions. The fermentation process occurs in microorganisms, which do not require oxygen to survive and reproduce. It also occurs in muscle cells, in the absence of oxygen, as an alternative to the citric acid cycle, which occurs in the presence of oxygen. In both cases, fermentation follows a process called glycolysis. Glycolysis breaks down glucose molecules from food and produces two molecules of pyruvate, which in the presence of oxygen will be converted to acetyl CoA and enter into the citric acid cycle; in a process commonly known as cellular respiration. However, in the absence of oxygen these pyruvate molecules enter into the fermentation process. The cycle of glycolysis and fermentation produces much less cellular energy than that of cellular respiration. Lactic acid fermentation in muscle cells leads to the synthesis of NAD+, which an electron acceptor, and lactate, while fermentation in yeast leads to the synthesis of NAD+, CO2, and ethanol. It is important to note that NAD+ produced is essential for the continuation of glycolysis, which produces ATP (cellular energy). However, the lactate, CO2, and ethanol produced are waste products of the process. Rumen fermentation, similar to the process that takes place in muscle cells and yeast, is outlined in more detail in the section below. (Information in this paragraph was obtained from Alberts et al. 2010) Rumen Fermentation Rumen fermentation is the process by which rumen microbes metabolize fibrous plant material, containing cellulose and hemicellulose, other carbohydrates, proteins, and fats to produce cellular energy and waste products valuable to cattle. As mentioned above, the rumen of a steer is colonized by a wide variety of microorganisms. These microbes include both protozoa and bacteria. Protozoa are “free-living, non-photosythetic, motile eukaryotic organisms” (Alberts et al. 2010, G: 18). Rumen protozoa ingest soluble sugars, starches, and some cellulose. Both the sugars and starches are converted and stored as starches, while the cellulose is converted to sugars (Hungate, 1975, p. 41). Rumen bacteria, which are prokaryotic, are much smaller than protozoa. Although there are types of rumen bacteria that digest all different types of carbohydrates, proteins, and lipids, they most importantly digest cellulose and hemicellulose, which is of primary importance in rumen digestion (Herd). In rumen microbes, organic compounds, including carbohydrates, fats, and proteins, are broken down via fermentation. As explained in the section above, this fermentation process produces NAD+, which enables the continuation of the energy producing pathway of glycolysis. Thus, the rumen microbes utilize the cattle’s feed to survive and reproduce (Hungate, 1975, p. 44). However, while creating energy for themselves, the microbes also generate waste products that are of great importance to the nutrition of the steer (Hungate, 1975, p. 44). These waste products include volatile fatty acids (VFAs), vitamin B, CO2, and methane gas (Hungate, 1975, p. 44). Fatty acids are carboxylic acids, a type of organic acid, that are characterized by the presence of a carboxyl group. Volatile fatty acids are fatty acids with a carbon chain of six or fewer carbons. The three most prominent VFAs produced in rumen fermentation are acetic acid, propanoic acid, and butyric acid (Hungate, 1975, p. 44). Although all of the volatile acids are absorbed through the rumen wall, or epithelium, into the blood stream, each VFA has a distinct metabolic destination. Little acetic acid is removed from the blood stream by the liver, and instead is oxidized to generate ATP throughout the body (Bowen, 2006). The liver almost completely removes propanoic acid from the blood stream, where it becomes the major substrate for the glucose generating process of gluconeogenesis (Bowen, 2006). This production of glucose is essential because the majority of the glucose ingested as food goes through the fermentation process and thus is not absorbed as might be expected in the small intestine (Bowen, 2006). The absorption of propanoic acid followed by the process of gluconeogenesis is a steer’s main source of carbohydrate. Although ruminants do not require as many carbohydrates as monagastric animal, these carbohydrates are still important components of a steer’s nutrition (Bowen, 2006). Butyric acid, similarly to acetic acid, after absorption into the blood is oxidized in a variety of tissues (Bowen, 2006). These volatile fatty acids produce approximately seventy-percent of a steer’s energy supply and are thus their production by rumen microorganisms is of great importance (Bowen, 2006). Although fermentation that results in methane still results in the synthesis of cellular energy for the microbe, this waste product is of no use to the steer. Even though the methane waste product does not benefit the steer, these microbes are still beneficial because they are often a direct source of energy to the steer (Bowen, 2006; Herd; Hungrate, 1975). As Round and Herd describe, “the microorganisms also pass from the rumen to the lower digestive tract, where

corn-based diet? Although we will never be able to conclude whether animals feel emotions, such as happiness, we do know they experience pain and science has shown that a corn based feedlot diet causes pain in cattle. If scientific research shows that a corn-based diet is inhumane, why does this practice continue? The answer lies in the government policies that surround the production of corn in the United States. These policies require that farmers continuously increase production in order to make even the slightest profit. Thus these government regulations encourage the overproduction of corn. This corn must go somewhere and thus industry has found a way to incorporate it into traditionally corn free products, including corn-fed beef. Since the over production of corn originated from government regulations, it may appear that fixing this problem may also have to originate from government policy. However, this is not necessarily the case. As consumers, Americans can vote with their wallet. By refusing to buy corn fed beef and supporting grass fed cattle farms, we can point out that we do not support the inhumane production of meats. If we regain contact with the way our food is produced, we can help improve the health of the animals we eat, our health, and the health of the environment. References Alberts et al. (2010). Essential Cell Biology (3rd ed.). New York: Garland Science. Britton, Robert & Rick Stock (n.d.). Beef Cattle Handbook: Acidosis. Retrieved November 29, 2010, from http://www.iowabeefcenter.org/Beef%20Cattle%20Handbook/Acidosi s.pdf. Bowen, R (2006). Pathophysiology of the Digestive System. Retrieved November 29, 2010, from http://www.vivo.colostate.edu/hbooks/pathphys/digestion/index.html. Canada Connects (2008). Getting Started with Chemistry. Retrieved December 9, 2010, from http://www.canadaconnects.ca/chemistry/10083/ Herd, Dennis B, &Whitney Rounds (n.d.). Beef Cattle Nutrition: The Cow’s Digestive System. Texas Agricultural Extension Services. Hungate, R. E (1975). The Rumen Microbial Ecosystem. Annual Review of Ecology and Systematics , 6, 39-66. Mallery, Charles (2010). How Cells Make ATP. Retrieved December 9, 2010, from http://www.bio.miami.edu/~cmallery/150/makeatp/makeatp.htm. Milk Composition and Synthesis Resource Library. Retrieved December 9, 2010, from http://classes.ansci.illinois.edu/ansc438/milkcompsynth/milksynth_lac tosecarbmetabol.html Shaw, J.C. et al (1960). Relation of Diet to Rumen volatile Fatty Acids, Digestibility, Efficiency of Gain and Degree of Unsaturation of Body Fat in Steers. The Journal of Nutrition, 71, 203-208. The Cow as an Herbivore and a Mutualist. Retrieved December 9, 2010, from http://www.nicksnowden.net/Module_3_pages/The_Cow_as_a_Herbi vore_and_mutualist .htm. Note: Eukaryon is published by students at Lake Forest College, who are solely responsible for its content. The views expressed in Eukaryon do not necessarily reflect those of the College. Articles published within Eukaryon should not be cited in bibliographies. Material contained herein should be treated as personal communication and should be cited as such only with the consent of the author.

The Impact of Corn-Based Diets on Cattle: A Health and Ethical Issue, Exams of Ethics

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Download The Impact of Corn-Based Diets on Cattle: A Health and Ethical Issue and more Exams Ethics in PDF only on Docsity!

A Difficult Reality to Digest: The Effects of a Corn-Based Diet on the

Digestive System of Cattle