Choosing a Summer Annual Forage
Livestock producers in diverse production environments have long used summer annual forages to produce hay and for supplemental pasture. However, some producers may not be aware of the variety of summer annuals available and how different species may suit different purposes.
"Generally speaking, the choice of summer annual planted depends on the intended use of the forage — whether it will be grazed or harvested as hay or silage," says Bruce Anderson, University of Nebraska forage specialist. "Depending on the purpose, there may be two, three or more choices that fit best."
Assuming a producer wants to supplement permanent pasture or range, by planting a summer annual for grazing, Anderson says two choices bear consideration. Sudan Grass is relatively fine-stemmed and palatable, especially brown midrib (BMR) varieties. Sudan Grass exhibits tillering, rapid regrowth and can work well under rotational grazing. The risk of prussic acid poisoning when grazing Sudan Grass is low, compared to forage sorghum or sorghum-Sudan hybrids.
Another popular choice for grazing is pearl millet, which is better adapted to the hot summers of the southern U.S. Pearl millet produces a leafy, high-quality forage without risk of prussic acid poisoning. With adequate moisture, regrowth is good.
For producers planning to make silage from a summer annual, Anderson says higher grain-producing varieties of forage sorghum and pearl millet are the best choices, offering maximum tonnage yield.
Any summer annual could be used for hay production, but Anderson says certain types often fit a particular niche. Sorghum-Sudan hybrids can produce two or three cuttings of hay, depending on season length and moisture availability. They typically yield more tonnage than Sudan grass cut for hay. There is a danger of prussic acid poisoning when grazing sorghum-Sudan hybrids, but not when cut for hay. With the noted climate adaptation, pearl millet performs comparably with sorghum-Sudan when harvested as hay.
Foxtail millet is different. Displaying more rapid development, foxtail millet varieties are better adapted to a short growing season. Often chosen as an emergency hay crop, they can work well in dryland situations. While foxtail millet makes pretty good hay, it offers only one cutting. But that can make it a good choice for a double-cropping strategy.
"After harvesting the hay, a producer can follow with a seeding of alfalfa or winter wheat, even drilling into the stubble, without worrying about killing regrowth from the previous crop," Anderson explains.
Teff is a summer annual that is gaining popularity for production of very fine-stemmed, high-quality hay of superior palatability. It's readily accepted by typically fussier companion animals, including horses, llamas and alpacas. Because of the quality and palatability, Anderson says teff hay also works well for weaning calves, or in heifer development rations.
Anderson says it's important for producers to understand the prussic acid poisoning risk associated with some summer annuals, but also the risk of nitrate toxicity. Under drought conditions, both sorghum-Sudan hybrids and pearl millet have the potential to accumulate high levels of nitrates, especially if they have been fertilized with nitrogen. The danger of toxicity is highest when grazing during a drought or when feeding hay that was cut during or immediately following a drought.
"Testing your forage is a good practice," Anderson states. "The test is relatively inexpensive compared to loss of livestock."