Maximizing the Value of Summer Annuals in Forage Systems

Understanding Trait Options

Modern summer annual hybrids offer a range of traits that improve forage quality, management flexibility, and livestock safety. Understanding how these traits work can help producers make informed decisions based on their operational goals.

Brachytic Dwarf summer annuals express a gene that shortens the internodes between leaves, resulting in a plant with significantly reduced height. Despite being shorter, brachytic dwarf varieties produce the same - or even more - leaves compared to taller, non-brachytic counterparts. These plants also tend to have more tillers, providing a dense, leafy canopy. Their compact stature improves standability and reduces the risk of lodging, while also making them easier to harvest with a lower cutting height. These characteristics make brachytic dwarf hybrids especially well-suited for grazing systems and areas where harvesting equipment may be limited by topography or moisture.

Brown Mid-Rib (BMR) is a naturally occurring gene mutation that reduces lignin content in plant cell walls. Lower lignin improves fiber digestibility (NDFd), increasing the energy available to livestock from each ton of forage. The BMR trait is particularly valuable in operations focused on producing high-energy feed. Modern BMR hybrids are not only suitable for heifer and dry cow diets but are also capable of delivering exceptional milk production and weight gain in lactating dairy and finishing beef herds. This trait is now widely available in multiple summer annual species and can help raise the overall nutritional value of a forage program.

Male Sterile (MS) hybrids are characterized by the absence of anthers, which prevents pollen production and grain development. These plants channel their energy into vegetative growth instead of seed production, leading to higher concentrations of sugar and protein in the stems and leaves. MS hybrids often exhibit improved standability and are ideal in systems where starch is not desired—such as when feeding dry cows, youngstock, or high-forage rations. Because no grain is formed, the forage produced is more uniform in quality and easier to ensile or graze without concerns about excess energy from starch.

Photoperiod Sensitive (PPS) hybrids remain in a vegetative growth stage until the day length drops below approximately 12 hours and 20 minutes—usually in mid to late September. This trait delays flowering and allows the plant to continue producing leaves and stems, effectively extending the growing season. The result is improved flexibility for harvest scheduling, a longer window for forage quality retention, and the ability to accumulate more dry matter without compromising nutritional value. PPS hybrids are particularly useful when planting timing is variable or harvest capacity is limited.

Prussic Acid Free (PF) hybrids are bred to not produce dhurrin, the compound responsible for forming toxic hydrogen cyanide (HCN), also known as prussic acid, under stress conditions. In typical sorghum, sorghum-sudangrass hybrids, and sudangrass, a killing frost or extreme drought can trigger dhurrin to convert into prussic acid—posing a significant health risk to ruminant livestock. Although prussic acid toxicity can be managed through harvest timing and wilting practices, PF hybrids eliminate this risk entirely. They allow for safer and more flexible grazing or greenchop use, even under weather stress, and reduce the time and labor required to manage animal movement or wait for detoxification periods. PF traited hybrids bring added peace of mind to producers operating in drought-prone or frost-risk areas.

Trait Comparison Table