Switchgrass has potential to be used as a dual-purpose crop for renewable energy and beef production. But its quality drops fast as it matures, so it should be cut before boot stage if the hay will be fed to growing cattle, say University of Kentucky researchers.

They harvested Alamo and Cave-In-Rock switchgrass at late-vegetative, boot and early flowering stages at two locations, then feeding trials were conducted at Eastern Kentucky University. Twenty-four Hereford-Angus steers were used in each of two trials.

Crude protein of Alamo hay ranged from 13.45% for late-vegetative hay to 5.12% for early flowering hay. Cave-in-Rock hay went from 11.32% to 4.82% crude protein as it matured, and crude protein digestibility also dropped in both varieties between the earliest and latest harvest stages.

Alamo’s NDF increased from 59% to 64% from the earliest to the latest cutting, and Cave-In-Rock’s went from 59% to 65%.

Dry matter intake was also affected, dropping nearly in half as the grass matured. Due to the lower intake, lower protein levels and reduced protein digestibility, the researchers say protein supplementation will be needed.

“Delaying the hay harvest will reduce beef steers’ ability to utilize switchgrass hay most efficiently and reduce the benefit obtained in growing switchgrass for hay,” they wrote.