In the back country ranges of the Rocky Mountains, ranchers such a Bob Brownlee have been fighting a constant battle against winter this year.

On a recent day when the temperature was near zero, Brownlee and his son-in-law, Newell Geers were hacking a hole in the frozen creek with a double-edged axe to find water for the cow herd, and giving out whoops of joy when a trickle of water appeared. Then they were off in their pickup truck, bumping across a washboard pasture and dropping off hay for the animals.

It was all part of the cycle of work at the far end of the country's beef pipeline, the $20-billion-a-year system that keeps Americans supplied with the juicy steaks and hamburgers that are almost a national symbol of American affluence.

Yet raising beef animals today is anything but a sure way to prosperity.

The threat of economic ruin hangs over the cattle industry, and the American beef economy is in the throes of major changes brought about by the heaviest losses since the Dust Bowl days of the 1930s.

Even in this remote valley, circled by mountains and once populated mainly by prairie dogs, antelopes and Indians, ranchers are feeling the painful effects of sweeping economic and social developments over which they have had virtually no control.

Brownlee reckons that he lost $30,000 on his 1 500-acre operation in 1976, and he may have been lucky. As far as he is concerned consumers are getting a bargain on beef while he has been taking a financial beating. Brownlee and the ranchers around here have lost money most of the last 36 months. Yet the price of steaks and hamburgers in supermarkets is about what it was three years ago.

Paradoxical as this situation may seem, economic analysts say it is logical. But the same logic holds that the situation is certain to be reversed. Then it will be the turn of American consumers to pay more for beef.

Starting in 1967, cattlemen steadily increased the size of their herds, from 108 million head then to 131 million head in 1975.

By late 1973, there was too much beef going to market. Retail stores had to keep prices low in order to sell it all. These low prices were passed back through the beef pipeline to wholesalers, meat packers, cattle fattening yards, and finally to ranchers.

All through the period, inflation and higher prices of hay, corn and other animal feeds were adding to the costs of running ranchers and farms, even as the prices that the cattlemen received when they sold their young steers and heifers in the fall was staying too low to make money.

Ranchers began reading the economic message they were getting two years ago and reacted by reducing the size of their herds. Since then, a beef slaughter unprecedented in the history of United States has been under way.

IN 1973, only 33 million animals were butchered. The number jumped to 36 million the following year, then to a record 40 million in each of the next two years. The total number of cattle in this country declined in 1976 by 4 million. More important than that, the country's cow herd - the "factory" that produces tomorrow's steers and heifers - has been drastically depleted.

In 1976, 10 million cows were killed about twice as many as three years earlier. Most of them were ground up for hamburger meat.

Consumers have been the immediate benefactors of this massive slaughter. It has helped ot hold down beef prices at a time when everything else seems to be going up.

Consumers ate up all the meat that came to the market, but only after retail stores had set a price for it that was low enough to induce them to buy. Americans tend to spend a constant 2.5 per cent of their money for beef. When it is a good bargain they buy more, and when it is expensive they switch to other food, such as cheaper pork or chicken. With beef prices fairly reasonable in 1976, they ate a record 129 pounds per person, compared with 116 pounds four years earlier.

In effect, Americans are eating their way out of a huge surplus of beef.

Brownlee and ranchers such as him still have a fundamental faith in the laws of supply and demand. They figure that when less meat goes to market, prices should start to rise again and they can begin turning profits.

But nobody knows for sure when the losses will end in the cattle industry. If the prices of steak and hamburger rise too abruptly, consumers might switch to pork, poultry, or even spaghetti. That happened in the 1973 beef boycott, and it sent prices plummeting. If it happens again, it could signal a fundamental change in the American diet.

Americans have eatena steadily increasing amount of beef since 1920, but there are at least some signs that the trend is ending. If it is, cattlemen could be in for some further unpleasant shocks.

In the 90 years since settlers moved into this valley the grassy ranges have been fenced, a railroad spur has been driven through from Wyoming, and oil and coal companies have dug wells and opened surface mines. But cattle is still a mainstay of the economy.

At Brownlee's Bar-Slash-Bar ranch, the cycle of breeding and birth sets the agenda for the farm work. The 550 cows in the herd will have their calves in April. Brownlee, Geers and a hired hand will take up a 24-hour vigil then, checking on the mothers and calves and scaring off intruding coyotes with spotlights. It costs about $176 to keep one of the cows for a year. That is money down the drain when a young calf dies or is killed.

In August, the father and son-in-law will become cowboys, riding horses to round up cows and head them back to the pens around the barns for artificial insemination with bull semen.

They will also turn bulls loose in the herd as a failsafe measure in case the artificial breeding doesn't work. There are no second chances for cows. If they fail to get pregant, they are sent to the packing house.

This same breeding cycle also imposes a rigid, economic framework on the rancher's operations.

In a few months, Brownies will be making decisions that could have financial repercussions in 1980.

Thiw fall, Brownlee will decide how many of this spring's calves to keep as replacements for old cows sold for hamburger. These heifers won't be bred until the summer of 1978. THey will calve in the spring of 1979, and the steers or heifers they produce won't be ready for slaughter until mid-1980. Only then will Brownlee get a return, unless he decides to sell the animals when they are younger.

Brownlee finds himself locked into such a cycle now. He figures he needed to get 65 cents a pound for the 450-pound steer calves he was ready to sell last December. But the best offer he got was 36 cents a pound. Rather than lose money, he decided to place them in a fattening yard in Greeley, Colo. He says he needs 45 cents a pound for the fattened animals. But packinghouses were playing under 40 cents in late January.

Last fall he lost $26 a heat on the full-grown animals he sold to a packinghouse. At some periods in the last three years, cattlemen have lost as much as $100 a head, according to the U.S. Department of Agriculture.

The atmosphere was all gloom at a weekly cattle auction at the Greeley Producers Public Stockyards in January.

Standing in front of a big sign that said, "Enjoy Beef Everyday," a professional auctioneer called out asking prices and offers to rows of overalled cattlemen, as a cowboy cracked a whip and drove the animals into a sawdust covered corral. When the animals got rambunctious, cowboys in the corral stepped behind wooden barriers.

Tom Nix, a 61-year-old farmer from Eaton, Colo., sold 35 steers to another farmer, Don Anderson. Nix had bought the animals in September and "grained them," fed them corn for the last month, waiting for cattle prices to start up. But he had grown tired of waiting.

"I don't know how he (Anderson) can buy 'em and still expect to make money," he said.

The government doesn't have any exact estimates of the cattlemen's losses, but bankers say they are in the billions of dollars. The cattle industry is stretched financially to the breaking point.

Denver banker Ron Hays says the debts of ranchers and cattle fatteners are "staggering," because they have acquired huge long-term mortgages from banks to cover the costs of their losing operations.

Hays said that because of the great demand for money insurance companies such as Prudential, Connecticut General and Connecticut Mutual have moved aggressively into agricultural lending in the West, using land as collateral.

There have been few actual foreclosures of the kind that swept the West after the 1930's Depression. However, many hard-pressed cattlemen have had to raise money to keep operating by putting first and second mortgages on their property. This has been possible only because land values have risen rapidly.

The rising land values have, provided a safety net for the western cattlemen East of the Rocky Mountains, in Colorado, South Dakota, Oklahoma, and Texas, undeveloped pastureland that can be irrigated for crops has jumped in price from around $150 an acre to nearly $1,000.

Inflation, climate, and population growth have played a part in rising western land values, but sohas the increased return on crops such as wheat and corn after 1972.

Thousands of acres of grasslands have been switched to crops as prices of those grains rose.

The equation of land, crops and cattle does not nseem to be working to the long-range advantage of consumers. At some point, beef prices will have to reflect the price of the land on which the cattle are raised. If they do not, farmers and ranchers will find other uses for their valuable real estate. That can only mean less beef at higher prices.

NEXT: Protein factories.