MONUMENT, Colorado (AP) — Susan Popp was a manager at Hewlett-Packard and her husband was a pilot at the Air Force Academy when they decided to become bison ranchers.

Now the US bison industry is trying to encourage more people — be they veteran cattle ranchers or newcomers like the Popps — to start raising the animals to help meet growing demand nation-wide.

"People understand the health benefits of bison. More people are trying it," said Susan Popp, 42. "It's not quite so exotic."

Since they began more than a decade ago, the Popps' Black Forest Bison ranch boasts a herd of about 60 buffalo, and their store in Colorado Springs is looking for more bison suppliers.

"If things keep going with the demand growing the way it is, we need to get some more people out there raising buffalo," said Dave Carter, executive director of the Denver-based National Bison Association.

The industry, which touts the meat as a healthier, leaner alternative to beef, is offering an online "Bison 101" course, evangelising the benefits of bison to lenders and expanding mentoring opportunities for new ranchers.

But it may be a tough sell right now, as factors that are affecting other meat producers such as the cost of land and rising fuel and feed prices can be obstacles to starting a bison ranch.

In the past few years, the bison association has built demand among customers looking for locally supplied, lower-fat alternatives to beef, and more top chefs are starting to serve bison. Largely wild, bison can calve on their own and aren't regularly injected with antibiotics or hormones. They also do well in extreme climates.

Today, there are bison producers in all 50 states, with about 4,000 private ranches raising roughly 232,000 animals. But the 46,195 bison processed through USDA-inspected facilities last year was dwarfed by the estimated 128,000 animals processed daily in the beef industry. "It's a tiny part of American agriculture, but bison has been a part of people's diets on this continent for thousands of years, and there's a good reason for that," said Bob Dineen, who founded Rocky Mountain Natural Meats based in Denver.

The trade group estimates up to 70 million bison may have roamed North America centuries ago, but that figure dwindled to about 1,000 in 1900. The industry claims credit for helping the population rebound.

Annual sales at Dineen's company have increased from 700,000 pounds to more than two million pounds over the past five years. Revenues, expected to reach $30 million this year, have grown 10 percent to 20 percent over the past 10 years, said Dineen, who started his company in 1986.

The US Department of Agriculture reported average wholesale prices for prime slaughter bulls at $220.94 in March, up 22 percent from a year earlier, even as slaughter numbers in federally inspected plants rose at about the same rate. "There's no guarantees in this world, but we've seen this growth steadily and slowly," Dineen said. "As we enter new marketplaces and get a toehold, it's staying and continues to grow."

This is not the US's first bison boom, though. The industry thrived on sky-high animal prices during a down market for cattle in the late 1990s, but got too big before ranchers had enough customers wanting to eat buffalo. That led to a slump, worsened by years of drought.

The Popps had only three animals they kept on a friend's ranch during the boom. They survived the downturn by staying small and buying a herd only after prices plummeted. "We were still in the growing phase. We just didn't grow as fast," Peter Popp said. Meat industry veteran and Armand Agra CEO Bud Flocchini of Reno, Nevada, estimates prices for heifer calves reached $2,000 around 2000 before dipping as low as $200 in 2001-2004, partly due to drought that forced many ranchers to sell off their herds. He estimates a rancher could buy a calf today for $400 to $500.

The bison association long has been touting the high protein benefits of bison to health-conscious consumers. Dineen said Ted Turner's Ted's Montana Grill has made the meat more accessible while spreading the message that, no, bison are not endangered.

Generally, a pound of ground bison can cost twice that of prime ground beef at the supermarket. In Colorado, ground bison retails at up to $7 a pound.

The group's rancher recruiting efforts include an online primer called Bison 101 that gives tips on what age of animals to buy, when to vaccinate, fencing and other pointers. It also is trying to inform lenders about the industry's fortunes, saying that bison meat sales reached $239 million at the retail and restaurant level in 2006. Ultimately, it hopes to formalise the mentoring that industry veterans traditionally have offered newcomers, whether their backgrounds are in livestock, crops or something else entirely, Carter said.

Recruiting efforts are funded in part by major meat processors and rancher donations. Retired Army helicopter pilot Joe Osborn of San Antonio said he tasted his first bison steak in Amarillo, Texas, in the 1970s. Taking the Bison 101 course in the past few months reinforced his hopes of starting a ranching operation.

But he needs to find some land first.

"I'm trying to find something affordable and close enough to San Antonio," said Osborn, 47.

Bison graze grassland but have their diets supplemented when food is scarce, particularly in winter. In recent years, both the bison and beef industries have seen feed costs rise.

A few years ago, the Bud Flocchini family's Durham Ranch near Gillette, Wyoming, could buy range cake — food pellets made from grain byproducts — which supplements bison diets in winter for $120 a ton. "Now we've been told we're looking at $200 ton this next year," said Bud's son, John Flocchini, who manages the property.

The Popps get outside income. Susan Popp still works at H-P, and Peter Popp is an airline pilot instructor. Susan Popp said they have no regrets about starting a ranch.

"My husband and I, you talk about life dreams. That was something we both wanted to do," she said. "It's just beautiful. When you work full days and life gets to you, you come out here, you look at the way they run around ... It just makes my heart sing."