Graziers don’t have to worry about losing forage quality if their cool-season grasses get tall in summer, according to two Wisconsin studies.

“We’ve now separated our spring and summer grazing recommendations for cool-season grasses,” says Dennis Cosgrove, a University of Wisconsin-River Falls Extension forage specialist who conducted a two-year study. “We’ll stick with our recommendations for spring, but in summer, graziers can maximize yield and maintain quality by letting the grasses get taller.”

Using 150 relative forage quality (RFQ) as a benchmark, in spring producers should start grazing smooth bromegrass, orchardgrass and reed canarygrass at 10” tall and continue until they’re 4” tall. Grazing should begin at 6” tall for Kentucky bluegrass and perennial ryegrass and end at 2” tall.

Grasses form buds in fall that then become flower buds over winter in a process called vernalization, Cosgrove explains. Early spring growth can be very high in quality, but once seed heads begin to form from those buds, quality drops quickly.

“Cattle generally don’t like those seed heads, so I recommend removing them by clipping once they’re fully emerged,” he says.

After seed heads are removed, the grasses enter the vegetative growth stage and remain in it for several months. During that stage, his study revealed, the grasses maintain 150 RFQ scores or higher, even when they get up to 20” tall.

A study at the U.S. Dairy Forage Research Center in Madison yielded similar results.

“We were surprised at how high the quality was in those tall grasses during summer,” reports Geoff Brink, an agronomist there who managed the study.

The grasses mentioned earlier were selected for the studies “because they’re common in Midwestern pastures, and they also represent different growth patterns,” says Cosgrove. “For example, smooth bromegrass doesn’t tiller as early or as vigorously as orchardgrass, which puts out many tillers.”

Beginning in early May, plants were measured for height and quality every three to four days until they were fully headed, then they were clipped. The process was repeated to measure the relationship between height and quality during the vegetative growth stage.

While it’s good news that they maintain their quality, Cosgrove offers this caveat: “As those grasses get extremely tall, utilization still goes down because animals can trample a lot more of it. So there can be some harvesting and intake issues that go along with letting the grasses get quite tall.”

His work was funded by a Grazinglands Conservation Initiative grant.