In the Nebraska Sandhills, for instance, DeGroff explains the forage growth year runs May 1 to April 30. The rainfall year runs Oct. 1 to Sept. 30. By inputting the subpar moisture that clients received last fall, they could begin making adjustments to planned stocking rates for this spring and summer.

“Two months into the forage year, you can begin to project the number of demand days 10 months out,” Kothmann says.

For example, knowing how much of an effect short summer moisture will have on DD next winter means having enough time to adjust to it, be it destocking cows or weaning calves two months early.

“It allows you to make decisions very early and have confidence those adjustments will work,” DeGroff says. “What we’re looking for are early warning signals.”

In DeGroff’s part of the world last summer, on similar forage resources, yearlings were gaining 1.5 lbs./day at one place, and 2.3 lbs. /day at another. The difference was stocking rate. “With TGM, you can calibrate demand days to what your objectives are,” he says.

“The biggest mistake I see some managers make with carrying capacity is unfounded optimism,” Kothmann says. “TGM is designed to take the gamble out of running livestock on a forage resource so that you never have too many cattle for the available forage.”

Getting started

Agren, Inc. of Carroll, IA received a grant from USDA’s Risk Management Agency in 2004 to identify and develop software to help ranchers make better decisions and avoid drought risks.  After a nationwide review of possible programs, they selected TGM as the most appropriate program and entered into a partnership with Texas A&M University to develop, test and promote TGM as a tool to help producers manage around drought. You can download TGM at

TGM has been tested, evaluated and used by commercial ranches across the U.S. and in Mexico for more than 20 years. TGM is regarded by those who use it as the best kept secret in the business.

Producers can start with TGM during drought, in times of plenty or anywhere in between. Once initiated, Kothmann and DeGroff say it will take 2-4 years for producers to see its full effectiveness due to the requisite calibration mentioned earlier.

“TGM will give you sound data, but it’s not a quickie,” Kothmann says. “To calibrate TGM, pasture demand ratios (PDR) generated by TGM are compared to observed PDR values.”

According to DeGroff, the major stumbling block he encounters with producers first learning about the model is the use of DD rather than AU. If you currently think in terms of AU, he says you can use the same number as DD to get started.

Incidentally, DeGroff encourages producers to download and study the TGM Users Guide at the TGM website. It simplifies what may seem complicated otherwise.

“Ranchers adapt to this concept much easier than range scientists,” Kothmann says. “Range scientists think in terms of forage supply and they want to measure it. Ranchers, though, already think in terms of cattle demand relative to available forage.”

Unfortunately, even when it makes sense, Kothmann says more people talk about managing carrying capacity more effectively than taking the steps to do it.

“There are a few excellent managers out there, maybe 5%,” Kothmann says. “And there are a chunk of producers, 40-50%, who are pretty good managers by the seat of their pants, retrospectively. But that’s reactive.”