About 8,000 years ago, the relationship between cows and man began with the revolutionary advent of domestication in Mesopotamia, the Indus River Valley, and Africa. Discover how cows have altered human life, human biology, and the geography of the world. Buy the DVD. This film premiered February 22, 2004.

About 8,000 years ago, the relationship between cows and man began with the revolutionary advent of domestication in Mesopotamia, the Indus River Valley, and Africa. There were many possible candidates for the job but only the cow fit the specific criteria humankind needed: not too flighty, breeds well in captivity, grows at a good pace, not aggressive, requires a low maintenance diet. Our ancestors chose wisely: Cows provide just about all of our basic needs, from milk and meat to muscle.

Today there are about 1.5 billion cows in the world. In many different countries humans and cows have formed close relationships. In England, dairy farmer Mark Evans spends all of his waking time with his cows, milking, feeding, and otherwise nurturing them. The African Masai tribe believes that all cattle were given to them from the great god N’gai at the beginning of time — a belief which today remains at the heart of their culture. India is home to a quarter of the world’s cow population. One major reason for this is that India’s majority Hindu community reveres cows and considers them to be “second mothers.”

NATURE’s Holy Cow explores how we’ve changed the cow and how the cow has changed us.

To order a copy of Holy Cow, please visit the NATURE Shop.

Online content for Holy Cow was originally posted February 2004.

Background:
Cattle originally evolved over millions of years through a process of natural selection-also known as “survival of the fittest”-which made them adaptable to a wide variety of environments, including most of those inhabited by another highly adaptable species: humans. Once humans discovered how to domesticate cattle about 4,000 years ago, they began to selectively, or “artificially,” breed them for specific desired traits like meat and milk production. This resulted in animals fit less for survival in the wild than the satisfaction of human needs, but in purely genetic terms, the arrangement has proven highly successful for cattle. Cattle now thrive throughout the world in over 800 different breeds, each more or less successfully adapted to their environment and the needs of their human caretakers.

The excerpted clips from the NATURE episode “Holy Cow!” illustrate some of the naturally evolved and artificially selected attributes of cattle.

Suggested Focus Questions:

Clip 1: A Cow’s Digestive System

1. What role do microbes serve in a cow’s rumen?
2. Does this clip illustrate naturally or artificially selected attributes?
3. Why would a cow’s ability to eat grass make it ideal for human domestication?

Clip 2: Desirable Breeding Traits in Cattle

1. How many different breeds of cattle have humans created?
2. Would the qualities that make good beef cattle help them survive in the wild?
3. Besides milk and meat production, what other traits might humans wish to breed in cattle?

Clip 3: Different Breeds of Cattle

1. What might indicate that a cattle breed is adapted to cold climates like Scotland?
2. What do the different breed names refer to?
3. Why might “adaptability” be a desirable trait in a specific breed?

Downloadable QuickTime versions of the video segments:
(Note: To downoad a video, right-click on the video title and click “Save Link As…” or “Save Target As…” On a Mac, press the CTRL key and simultaneously click the mouse, then save the link.)

Clip 1, “A Cow’s Digestive System”

Clip 2, “Desirable Breeding Traits in Cattle”

Clip 3, “Different Breeds of Cattle”

GRADE LEVEL: Grades 9-12

TIME ALLOTMENT: Two to three 45-minute class periods

OVERVIEW: Cattle evolved through the slow process of natural selection until human domestication, which rapidly accelerated their development as an artificially selected species fit less for survival than to satisfy human needs. This lesson focuses on how and why humans have been so successful in selectively breeding cattle to suit these needs, while also exploring the limitations and consequences of this success.

Natural selection describes the process by which organisms best adapted to their environments are the ones that survive and reproduce. The Introductory Activity helps students understand that some traits, such as the ability to digest grass, made certain species more desirable for domestication by humans. The Learning Activities explore how, by nurturing and protecting animals that might not have survived in the wild, human domestication interrupted the process of natural selection. Reproductive success was no longer primarily determined by an animal’s most naturally adaptive survival traits, but rather by its artificially selected traits desirable to humans (primarily milk and meat production). The culminating activity presents a case study in which students consider the consequences of losing the naturally selected attributes of breeds less adapted to domestication.

Students should already be familiar with the concepts of evolutionary adaptation, natural selection, and DNA/genetic engineering.

SUBJECT MATTER: Biology/ Living Environment

LEARNING OBJECTIVES:

Students will be able to:

• Describe the traits of cows that make them suitable for domestication.
• Explain how the cow’s digestive system has adapted to its environment.
• Compare and contrast natural and artificial selection.
• Describe various breeds of selectively bred cattle and their desirable traits.
• Discuss some limitations and negative consequences of selective breeding.

STANDARDS AND CURRICULUM ALIGNMENT:

From the National Science Standards for Science Content, Grades 9-12.

CONTENT STANDARDS C: Life Science
As a result of activities in grades 9-12 students should develop understandings of:

Biological Evolution

• Species evolve over time. Evolution is the consequence of the interactions of (1) the potential for a species to increase its numbers, (2) the genetic variability of offspring due to mutation and recombination of genes, (3) a finite supply of the resources required for life, and (4) the ensuing selection by the environment of those offspring better able to survive and leave offspring.
• The great diversity of organisms is the result of more than 3.5 billion years of evolution that has filled every available niche with life forms.
• Natural selection and its evolutionary consequences provide a scientific explanation for the fossil record of ancient life forms, as well as for the striking molecular similarities observed among the diverse species of living organisms.

Behavior of Organisms

• Like other aspects of an organism’s biology, behaviors have evolved through natural selection. Behaviors often have an adaptive logic when viewed in terms of evolutionary principles.

New York State Core Curriculum Alignments
From the Living Environment Core Curriculum.

STANDARD 4: Students will understand and apply scientific principles and theories pertaining to the physical setting and living environment and recognize the historical development of ideas in science.

Key Idea 2: Organisms inherit genetic information in a variety of ways that result in continuity of structure and function between parents and offspring.

Performance Indicator 2.2: Explain how technology of genetic engineering allows for human to alter genetic makeup of organisms.

2.2a: For thousands of years new varieties of cultivated plants and domestic animals have resulted from selective breeding for particular traits.

2.2b: In recent years new varieties of farm plant and animals have been engineered by manipulating their genetic instructions to produce new characteristics.

Key Idea 3: Individuals and species change over time.

Performance Indictor 3.1: Explain the mechanisms and patterns of evolution.

3.1e: Natural selection and its evolutionary consequences provide a scientific explanation for the fossil record of ancient life-forms as well as for the molecular and structural similarities observed among the diverse species of living organisms.

3.1f: Species evolve over time. Evolution is the consequence of the Interaction of (1) the potential for a species to increase its numbers… (4) the ensuring selection by the environment of those better able to survive…

3.1j: Behaviors have evolved through natural selection. The broad patterns of behaviors exhibited by organisms are those that have resulted in greater reproductive success.

3.1k: Evolution does not necessitate a long-term progress in some set direction. Evolutionary changes appear to be like the growth of a bush: Some branches survive from the beginning with little or no change, many die out altogether, and others branch repeatedly, sometimes giving rise to more complex organisms.

MEDIA COMPONENTS

Video

NATURE, Holy Cow, selected segments:

Clip 1, “A Cow’s Digestive System”

Clip 2, “Desirable Breeding Traits in Cattle”

Clip 3, “Different Breeds of Cattle”

Access the streaming and downloadable video segments for this lesson at the Video Segments Page.

Web sites

Breeds of Livestock
An Oklahoma State University Web site featuring photos and descriptions of various breeds of cattle from around the world.

World Climate Map
A map of the world showing different climate zones.

Genetic Engineering
A Regents’ preparatory Web site featuring a description of how the meaty English Shorthorn cow was selectively bred with the heat-resistant Brahman cow to produce the Santa Gertrudis, a hybrid which possesses the positive characteristics of both parent breeds.

Punnett Squares
An interactive Web-site which explains how Punnett squares can be used to determine the likelihood that certain traits will be passed on to future generations.

A Dying Breed
A New York Times article which discusses the pros and cons of increasing hybridization by Bahiman cattle ranchers in Uganda of their native Ankole cattle with Holstein cattle from the United States.

MATERIALS

For each student:

• “Traits of Ankole and Holstein Cattle” Student Organizer (PDF)(RTF)

For each group:

• “Man’s Best Friend?” Student Organizer (PDF)(RTF)
• “Cattle Breeding” Student Organizer (PDF)(RTF)
• “Finding the Balance” Student Organizer (PDF)(RTF)

For the class:

• “Traits of Ankole and Holstein Cattle” Student Organizer Answer Key (PDF)(RTF)
• “Man’s Best Friend?” Student Organizer Answer Key (PDF)(RTF)
• “Cattle Breeding” Student Organizer Answer Key (PDF)(RTF)
• “Finding the Balance” Student Organizer Answer Key (PDF)(RTF)
• Computer with Internet access, projector, and screen

PREP FOR TEACHERS

Prior to teaching this lesson, you will need to:

Preview all of the video clips and Web sites used in the lesson.

Download the video clips used in the lesson to your classroom computer, or prepare to watch them using your classroom’s Internet connection.

Bookmark the Web sites used in the lesson on each computer in your classroom. Using a social bookmarking tool such as del.icio.us or diigo (or an online bookmarking utility such as portaportal) will allow you to organize all the links in a central location.

Next: Proceed to Activities.

In the increasingly industrial world of North American cattle production, organic farms are the exceptions. While other farmers send their calves off to crowded feedlots to be fattened on grain enriched with nutritional supplements, a new breed of alternative rancher is keeping their young animals close at hand, to spend their final months before slaughter on the green, green grass of home.

In NATURE’s Holy Cow, viewers visit one of the leaders of the “alternative” ranching movement, Colorado’s Lasater Ranch. There, the Lasater family is demonstrating that they can raise high quality, organic beef using methods that many experts say are friendlier to the environment — and healthier for beef eaters. And although skeptics doubt that such methods will ever supply most beef to consumers, others credit ranchers like the Lasaters with demonstrating the benefits of the “grassfed” movement.

Once, all beef cattle were grassfed — spending their entire lives grazing on farm fields or prairie. These days, however, beef calves typically spend the last few months of their lives in feedlots, where they are fattened on special feed, and often given drugs to ward off disease. Mainstream producers say such methods have helped guarantee a steady, reasonably-priced stream of meat to consumers.

Dale Lasater nurtures one of his cows.

Critics, however, say cheap meat has come at the expense of safety. They argue that the modern approach has had dangerous consequences, such as the spread of food-borne illnesses caused by bacteria, and even deadly “mad cow disease,” a fatal neurological disease caused by eating contaminated beef. Researchers believe mad cow is spread by giving cattle feed that includes bone meal and brain or spinal cord tissue taken from other diseased cows (that practice is now banned in the United States and other developed nations).

To avoid such problems, grassfed ranchers feed their animals only pasture grass, legumes, and hay. And while just a few consumers were once aware of the existence of such beef, a series of disease scares — including the late 2003 discovery of a “mad” cow in the U.S. that led to the destruction of hundreds of animals — has helped spark greater interest.

“The silver lining in this horrible situation is that it is getting people to think about what they are eating and how it is produced,” says Marlene Groves, president of the Colorado-based American Grassfed Association, an alliance of several dozen alternative ranchers and food purveyors.

Some consumers prefer grassfed beef because they believe that the production method is kinder to the environment and more humane to animals than large-scale commercial production. But others are interested in potential health benefits. “Nutritional research shows these products to be much higher in [beneficial chemicals], and lower in fat and cholesterol,” says Groves. And grassfed consumers “don’t have to worry about E. coli contamination,” she adds. (E. coli is a common bacteria that, in some forms, can be deadly.)

Such claims have helped increase demand for grassfed products. But the ranchers still face major challenges. Many major grocers don’t carry the products, forcing consumers to order them over Web sites or through specialty stores. There are few national standards that define true “grassfed” agriculture. And, so far, grassfed methods have proven to be more expensive than competing industrialized methods, relegating grassfed beef to niche markets.

Still, Groves is optimistic. “I think this may be the beginning of a revolution where people examine the evidence and make better choices for themselves and their families,” she says. “Ultimately, I believe this movement will benefit independent family producers, such as grassfed producers, who are more closely connected to the food they produce.”

As a skier and martial artist, Arnaud Eboli showed discipline, grace, and considerable athletic skill. So his family was mystified, then horrified, when the French teenager began exhibiting fits of rage and then started stumbling around his home in the late 1990s. Soon, he couldn’t remember things and his speech began to falter.

“It was as if his mouth was full of food and he couldn’t push the words out,” his mother told reporters. In April 2001, Eboli died — paralyzed and comatose — becoming one of the world’s roughly 150 known victims of “mad cow disease.”

First recognized in the United Kingdom in the 1980s, mad cow disease — formally known as bovine spongiform encephalopathy (BSE) — causes the brains of cattle to waste and become spongy and pockmarked. (A similar disease, scrapie, has been known to affect sheep for more than a century.) Stricken animals stagger and behave erratically — like “mad cows” — and eventually are unable to stand. Although BSE was recognized as a problem for farmers, it took a while for officials to realize that the disease might threaten people who ate beef, too. Only in the last decade have researchers been able to piece together much of the sobering story.

Today, scientists believe mad cow gained its foothold in the U.K. when farmers began giving their cattle feed which was laced with tissue from other farm animals, that included sheep and “downer” cattle. The tissue held hardy, misshapen proteins — called prions — that are believed to cause the disease by triggering changes in normal proteins. These prions can be transferred to people when they eat beef products that include infected brain, spinal cord, or intestinal tissue.

In infected people, the prions cause what doctors call “variant Creutzfeldt-Jakob Disease” (CJD) — the disease that killed Arnaud Eboli. It can take years for the disorder to fully develop and, so far, there is no known cure. In Britain, more than 140 deaths have been attributed to the disease. The first known human victim was Stephen Churchill, 19, who died in 1995.

Once the deadly chain was understood, first Britain and then other nations took drastic steps to stop the spread of mad cow. In the United Kingdom alone, almost four million cows suspected of carrying the disease were destroyed. Governments banned the sale of feed including tissues from other livestock. Many nations began testing programs, although the only certain way to know if a cow is infected is to study its brain after it dies.

So far, such steps have prevented other major outbreaks. But concern remains high. When the United States discovered a single infected cow in late 2003, for instance, there were profound repercussions. The discovery prompted a steep drop in beef prices, a ban on U.S. exports, and a nationwide search for other infected animals. Hundreds of animals were slaughtered in a bid to head off any potential outbreak.

Researchers continue to try to understand mad cow and invent better ways to detect it. The February 2004 announcement of a new strain of the disease, found in two Italian cows, may prompt the Department of Agriculture to adopt more sensitive tests already used in Europe. In the meantime, researchers warn that everyone from farmers to consumers need to keep a watchful eye on what they eat — and what it, in turn, was fed.

In NATURE’s Holy Cow, viewers meet John Webster, a British expert on cattle and animal welfare. Webster, a former president of the British Society for Animal Science, was one of the researchers asked by the British government to study the causes and consequences of mad cow disease. In 2004, NATURE spoke with Webster about the past, present, and future of cows from his home, which overlooks one of England’s many dairy farms.

In Holy Cow, the Lasater Ranch is used as an example of a more ecologically sustainable and more humane way to raise cattle. Is it the wave of the future?

Well, the Lasater Ranch is producing the equivalent of Fabergé eggs — a very high quality product for which people are willing to pay something extra. But it’s not as different from the usual practices as it may look. The major difference comes in the last 150 days of the calf’s life; instead of being intensively fed corn and grain, Lasater Ranch calves feed on the range.

The typical method of raising beef in the United States probably will continue to spread to other parts of the world, in areas where it makes sense: where the breeding cows can get most of their food out on the open range, and the calves to be slaughtered spend the last part of the cycle being intensively fattened. Often, it’s the best use of the land. It’s a very effective way of transforming plants we don’t eat into something we do like to eat. I’m not saying it’s the most admirable method, but that it works very well and is likely to continue.

John Webster

In general, where do you see cattle operations headed?

Due to concerns about mad cow disease and animal welfare, I think there will be an increasing trend toward marketing steaks so that [the consumer] knows exactly which farm or farmer they came from. Some sources will be perceived to have higher quality.

As far as the welfare issue is concerned, however, the problems with beef cattle are nothing compared to the problems in the dairy industry. So anyone who avoids beef and elects to eat cheese due to welfare concerns is missing the point.

Where would you like to see things headed?

I’m not too concerned about beef, but the dairy industry is a big concern. In dairy, I believe the industry needs to “redesign” the cow. The approach with American Holstein dairy cows has just gone too far. The cows are very productive, and the system looks cost effective in the short run, but it uses the cows up way too quickly. On strictly economic grounds, cows should be lasting at least four lactation cycles, but it takes just two or two and a half cycles to use up current cows. An awful lot of cows are culled after that.

And it’s not just me crying wolf — the industry has realized things have gone too far. They are looking at changing the way cows are selected, trying to maintain milk production without getting a bigger and bigger cow that can’t hold herself on her feet. It’s a real shame to see these young animals glowing in good health, and then seeing them turn into old crones within a year.

What do we know now about the origins of mad cow disease, and ways to prevent it?

I was on a committee here in the U.K. that studied the issue, and nobody really knows the origins for certain. It may have always been with us at a very low level, people just didn’t notice. But our farming practices multiplied it, particularly by giving young cows feed that included infected material, such as bone meal, from other cows. Studies show the vast majority of our cows were infected as young animals from material that was in their starter rations. That was pretty much unique to the U.K., and probably why we had a bigger problem than the rest of Europe. But if it is true that mad cow has always been here, it may never go away completely.

Are there still major differences in the way cows are raised in the U.S. and Europe?

Fewer and fewer. Traditionally, in Europe the cow took most of its food off the land. But it is becoming a lot more like the U.S., with grain coming in at the end of the cycle for beef cattle.

Have we reached the end of the road in cattle breeding, or will new engineering technologies produce new “super cows?”

Well, it depends on whether you are talking about beef or dairy. We’ve discussed dairy. In beef, however, you are really selecting for different things in the animals you are going to slaughter for meat, and the animals you are going to use for breeding. The best cow is not the best slaughter calf. In the calves you want muscle, and you want them to get large. The cows need to stay fat over the winters. So anyone who thinks you can breed one perfect cow for everything is headed in the wrong direction.

The cow has become a cultural icon in the United States. Companies put it on their products, and cow memorabilia is a huge craze. What accounts for that?

You know, the great thing about the cow is that she can eat plants we don’t, on land the farmer might not own, and convert milk into cash for the farmer. So a cow was often the most valuable thing a farmer owned. Even during a drought, they would hold some value. So cows became an icon for value; they were simply the most valuable animal around. And in modern times, there is still the image of the cow as a rural animal, a symbol of what the poet Blake called “the green and pleasant land” of England where we built our “Jerusalem.”

It’s becoming a routine ritual on the crowded, colorful streets of Delhi, India: A small team of men surrounds a wandering cow, attempting to coax it on to a waiting truck for a trip to a suburban reserve. But the cow catchers need to be careful: To India’s millions of Hindus, the cow is a holy animal that cannot be harmed.

The tender treatment is just one example of our complicated relationship with cows — a historic partnership detailed by NATURE’s Holy Cow. From a source of meat and milk to a provider of labor and religious inspiration, cows often play a central role in modern life.

Few people, however, revere the cow like the world’s 900 million adherents of Hinduism. Since the faith first evolved near Asia’s Indus River more than 3,000 years ago, respect for animal life has been a central theme in Hindu life. While many scholars say early Hindus ate beef, most ultimately came to see the cow as a sacred animal to be esteemed, not eaten. “If someone were to ask me what the most important outward manifestation of Hinduism was, I would suggest that it was the idea of cow protection,” Mahatma Gandhi, India’s legendary nonviolent leader, once wrote.

Although Hindus follow no single set of rules, reverence for cows can be found throughout the religion’s major texts. Some trace the cow’s sacred status back to Lord Krishna, one of the faith’s most important figures. He is said to have appeared 5,000 years ago as a cowherd, and is often described as bala-gopala, “the child who protects the cows.” Another of Krishna’s holy names, Govinda, means “one who brings satisfaction to the cows.” Other scriptures identify the cow as the “mother” of all civilization, its milk nurturing the population.

Today, in heavily Hindu nations like India and Nepal, milk continues to hold a central place in religious rituals. And in honor of their exalted status, cows often roam free. Indeed, in some places, it is considered good luck to give one a snack, a bit of bread, or fruit before breakfast. On the other hand, a citizen can be sent to jail for killing or injuring a cow.

The divine bull, Nandhi, guards Hindu temples.

But as cities have grown more crowded, cow-friendly policies have posed problems. Delhi’s 13 million residents, for instance, share the streets with an estimated 40,000 cows — leading to some complaints. One is that the grazing cows spread trash as they rip open garbage bags in search of tasty morsels. Another is that they dangerously snarl traffic.

“What is the greatest traffic hazard in Delhi today? Cows,” Bibek Debroy, a columnist for India’s Financial Express, wrote in a pointed 2003 essay. “As our national animal, the tiger may be close to extinction. But the cow is very much around and many soon become our new national animal.”

To solve the problem, Debroy offered one tongue-in-cheek solution. “Let them have reflectors and, if not license plates, at least identity cards. Only genuine Delhi cows should be eligible for social security and other benefits.”

City officials, meanwhile, have adopted a different approach: the cow catchers. Under pressure to reduce cow populations, Delhi has hired nearly 100 of the urban cowboys, who are charged with catching and shipping cows outside the city limits, sometimes to special reserves where the animals are cared for.

But the work isn’t easy. And it can be downright dangerous. The cows often sport sharp horns, and life on the street has made them savvy and sometimes ornery. Some can recognize the sound of the transport trucks and perform a kind of bovine ballet to avoid the catchers. Still, city leaders say they won’t give up until the vast majority of the cows have been moved. Skeptics note that some of the animals return to their home turfs within days of being moved.

Meanwhile, some of India’s Hindu politicians are relying on cows to bolster their support. They have proposed new cow-protection ordinances, and vowed to ban butchers from Indian stores. Critics say such proposals go too far, and would violate India’s commitment to religious tolerance — and the nation’s constitution. But if cows could vote, they’d surely be in favor.

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