One of the fundamental rules of thumb in pasture management is “take half and leave half.” “The problem is,” says Tim Steffens, Texas AgriLife Extension Service rangeland specialist in Canyon, TX, “the cows did not read the book.”

Cows, being cows, take the best half and leave the rest alone. And that means, Steffens says, you can be conservatively stocked and still overgraze a pasture.

The question is, how do you know? Steffens says there’s an easy and simple way to eyeball a pasture and get a sense of how well it’s doing. The system isn’t meant to replace more long-term analytical tools, like transect lines and monitoring exclosures, but it’s a useful tool to help you make short-term assessments and rotational grazing decisions.

Called the Grazing Response Index, it uses three concepts related to plant health—frequency of defoliation, intensity of defoliation and the opportunity for the plant to regrow after being grazed. The index uses a +1, 0 or -1 scoring system.

“For frequency of defoliation, if you’ve had zero or one defoliation in a growing season, that’s a +1,” Steffens says. “If you’ve got two, that’s a 0. If you’ve got more than two, that’s a -1.”

Intensity of defoliation, he says, is how much is taken. But be careful in your evaluation. “You don’t want to get wrapped around the axle. I have watched grown men argue about whether a plant is 35% defoliated or just 30%. And neither one of them knew.”

But, he says, you can look at a plant and say it’s been grazed too tight. So, lightly grazed is a +1, moderate is a 0, and severe scores a -1.