CHEYENNE, Wyo. (AP) — Wyoming's cattle population dropped 21 percent during the past decade as ranchers struggled through a persistent drought that gripped much of the state from 1999 until last year.

The cattle count in Wyoming dropped from 1.66 million in 1998 to 1.3 million in 2008, according to the newly released 2009 Wyoming Agricultural Statistics report. This January's count was up 3 percent from the year before.

The United States Department of Agriculture, the Wyoming Business Council and the University of Wyoming produce the annual report.

Wyoming is particularly sensitive to drought cycles because ranchers in the state rely heavily on grazing forage rather than irrigated pastures or croplands, agriculture officials said.

"When we have drought, we just don't have the carrying capacity out on the range, you can't put as many out there," said Jason Fearneyhough, Wyoming Department of Agriculture director. "So people have got to sell off cattle to maintain the range and also to maintain the economic viability of their place."

A drought ranging from moderate to severe gripped Wyoming — the nation's fifth driest state — starting in 1999 until conditions eased in mid-2008, according to the State Climate Office. Last year saw improved but spotty moisture around the state, while 2009 has been a plentiful year for mountain snowpack as well as spring and summer rains.

"When you reduce cattle numbers by about 300,000, it will take quite a while for the ranchers to rebuild those herds," Fearneyhough said. "They're pretty particular about their genetics in each operation, and so it'll take some time to build back up to that forage that's there."

Ed Perry, a rancher in Goshen and Niobrara counties of eastern Wyoming, said his operation reduced its cow-calf pairs by 50 head during the dry years.

"It's been tough. We have scrambled I can't tell you how many years," Perry said.

He said most of his neighbors also reduced their herds.

"If they kept their original numbers, their pastures were abused or grazed really short or they had to get supplemental feed elsewhere," he said. "Even with our numbers down, we've had to find other grass and also additional feed."

Drought pushes up the cost of feeding animals because hay prices go up and the cost of pasture leases increase as more ranchers look for places to graze their animals, said Steve Paisley, state beef extension specialist at the University of Wyoming.

Jim Magagna, executive vice president of the Wyoming Stock Growers Association, said drought can be a contributing factor to other trends that have driven down the state's cattle population. Those include ranchers selling their land for other uses, such as subdivisions, or elderly ranchers selling their herds and retiring.

Perry said he hasn't yet tried to rebuild his herd to pre-drought levels because he's waiting to see whether the moisture and grass growth of this year continue into the future.

"If it continues to stay in this normal pattern we'll increase our numbers back up to where we were," he said.