Prairie hay is mostly warm-season grasses like the bluestems and gramas, indiangrass, switchgrass, lovegrass, or prairie sandreed. There might be some wheatgrass or junegrass or other cool-season species present. One factor to consider when timing harvest of prairie hay is stand persistence. Producer experience and University research both show that prairie hay stands decline rapidly if they are often harvested twice a year. Another factor is hay quality. Prairie hay cut in late June or early July might have over 10 percent protein and 65 percent TDN. As grass increases in maturity, grasses develop seedheads and stems, and forage quality will decline. If you wait until August to cut, protein might drop down as low as 5 percent and TDN as low as 45 percent.
Other practical considerations might be your difficulty harvesting all your prairie hay at once and your potential need for both high quality hay for young stock and average quality hay for dry cows. This means that most operations should have at least two different prairie hay stack yards. In one stack yard have prairie that was harvested in late June or early July for high quality. In another stack yard or in a different area of the same stack yard, stack hay harvested in early August for high yield. For management next year, the area that was cut early this year should be cut in early August next year and the hay harvested in August this year should be cut in late June, early July next year.
Source: University of Nebraska-Lincoln