Warm-season annual grasses are a good way to provide forage that’s relatively high in nutrients, said Dirk Philipp, assistant professor with the University of Arkansas System Division of Agriculture.
Philipp said in Arkansas, warm-season annuals of choice are pearl millet, forage sorghums, sudangrass and sorghum-sudan hybrids.
While “each of these can be haying, grazing, or even silage,” he said, the forages have specific production techniques and uses.
Pearl millet “is leafier than the other grasses throughout the growing season and can also be safely used for horses,” Philipp said. Pearl millet is ready to graze when plants are 1 to 1.5 feet tall. It is, however sensitive to close grazing and “stubble of at least six inches should be left for good regrowth.”
“Where uneven grazing has occurred, clip stands to an even height to promote more even quality of regrowth,” he said. “
Pearl millet can be affected by high nitrate levels, which can be caused by high nitrogen fertilizer use, drought or freeze stress or drought plus nitrogen fertilizer application.
Pearl millet cut for hay will retain high nitrate concentrations and Philipp said if growers have any doubts about nitrogen levels, they should test the forage.
Sorghum-sudan hybrids have the advantage in showing high yields compared to pearl millet and also to other sudangrasses,” Philipp said. However, horses should not graze sudan or sudan-sorghum hybrids “as they can contract the so-called cystitis syndrome.”
Grazing on sorghum-sudan hybrids can begin if the plants are at least two feet tall.
“Like pearl millet, grazing should stop if the grasses are grazed down to six inches,” he said. “Regrown canopies should be at least 18- to 24 inches tall before being grazed again.”
Sorghum-sudan grasses can be high in prussic acid, which can be deadly if eaten in sufficient quantities. High concentrations can be attributed to drought or freeze stress and are found in leaves.
Philipp said “the potential for high prussic acid concentrations is high in the early growth stages of the grasses and short, leafy plants having the highest potential concentrations.”
If prussic acid concentrations are expected to be high in these grasses, Philipp recommends deferring grazing for at least one week and if hay is made from sorghum-sudan grasses, the prussic acid content can be reduced up to 70 percent by wilting prior to baling.
For more information about forage production, contact your county extension office, visit www.uaex.edu.