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.

At first glance, they look harmless enough. Africa’s helmeted terrapins often sit motionless in grassland water holes, silently watching the herds of animals that come to sip from their muddy homes.

But as NATURE’s The Reptiles: Turtles and Tortoises shows in vivid detail, the helmeted terrapin can be also be a surprisingly quick and agile predator. Working in packs, like wolves, groups of terrapins can corner and devour birds that pause too long by the water’s edge. One early biologist watched, stunned, as a pack of seemingly sleepy terrapins suddenly attacked a wading bird, “dragging it underwater to devour it.”

Such coordinated cunning may seem surprising for a turtle. But the world’s nearly 300 species have a remarkable range of behaviors, from wood turtles that stomp on the ground to attract worms, to sea turtles that can travel thousands of miles to lay eggs on the very beaches where they were born. Then there are the cleverly deceptive snapping turtles, which can have body parts shaped like wriggling worms or finning fish — all designed to lure prey to their doom.

This diversity isn’t surprising. After all, these shelled reptiles have had some 200 million years to evolve into today’s dazzling array of shapes and sizes. They live on all the world’s continents and in all the world’s oceans — except the frigid polar regions.

In general, there are three groups of turtles: Tortoises, which live on land but sometimes take a dip in water; terrapins, which live mainly in water but lay their eggs on land; and sea turtles, which spend much of their lives paddling about the ocean, but lay their eggs on beaches. There are 8 species of sea turtles, about 180 kinds of terrapins, and nearly 100 varieties of tortoises. The biggest turtle, the leatherback sea turtle, can grow to 8 feet long and weigh 2,000 pounds. The smallest, the southern speckled padloper of Southern Africa, can be just 4 inches long and weigh only a few ounces.

Turtles have held great significance in many cultures. Whatever their size, however, turtles have long figured large in the human imagination. Some tribes say the world was born on the back of a turtle. Some Hindus picture the universe being held up by four elephants — all perched on a turtle’s shell. Other cultures hail the turtle as a symbol of resilience and practicality, since it carries its home on its back. Folk tales celebrate its determination — such as when the speedy but overconfident hare is beaten in a race by a plodding but persevering turtle.

Unfortunately, turtles have also figured heavily in the human diet. Turtle soup and turtle meat are mainstays in some cultures, leading to the overhunting of some species. But just as big a threat comes from the destruction of turtle habitat, from the freshwater swamps that harbor many species, to the oceanside beaches where sea turtles must lay their eggs. Overall, nearly 3 dozen species are considered rare or endangered, including nearly all of the sea turtles.

Luckily, turtles have an increasing number of allies. Around the world, people are realizing that shells aren’t always enough to protect these remarkable reptiles, and are taking steps to save populations. Like Africa’s helmeted terrapins, these turtle protectors are learning that there is strength in numbers.