A growing number of beef and dairy producers are using summer annuals to boost available forage during midsummer. With improvements in breeding and selection, the BMR (brown midrib) trait has been incorporated into several forage species.Rocky Lemus, extension forage specialist with Mississippi State University (MSU), addressed the use of BMR warm-season annuals, such as sudangrass, pearl millet, and forage sorghum, for summer grazing in a MSU Forage News article.“Forages with the BMR trait tend to have improved forage quality that results in superior average daily gains in livestock,” Lemus explains. “Although fiber digestibility usually declines with plant maturity, BMR cultivars tend to have higher digestibility compared to conventional cultivars of the same summer annual species,” he adds.When comparing BMR hybrids to their conventional counterparts, BMR cultivars are higher in crude protein and digestibility and lower in lignin content. They also have higher in vitro true digestibility (IVTD). “Producers often ask how should species containing the BMR trait be agronomically handled,” Lemus notes. He recommends handling them like any conventional variety when it comes to fertilization, harvesting, or grazing.Some adjustments that may be needed are planting in soils that are 60 to 65°F and altering the seeding rate to ensure adequate stem size to prevent lodging in certain situations.While more instances of lodging can be observed in BMR hybrids, data from Texas A&M shows that the occurrence of lodging is in a similar range with that of other sorghum types.For forage sorghum, Lemus recommends a seeding rate of 15 to 20 pounds per acre. A rate of 25 to 30 pounds per acre is best for sudangrass, sorghum-sudangrass hybrids, and pearl millet.Apply potassium and phosphorous according to soil test recommendations. For a grazing system, 30 to 40 pounds of nitrogen per acre is sufficient. An application of 40 to 50 pounds of nitrogen per acre per each cutting cycle is recommended for hay production.Grazing at 24 to 30 inches or cutting at 36 to 48 inches is ideal for the majority of BMR species, says Lemus. When cutting, he reminds producers to leave a 4 to 6 inch stubble height to allow for proper regrowth.While allowing forages to go beyond the recommended height boosts yield, it usually leads to lower crude protein and energy levels.Allow adequate time for drying when making hay with these species; they tend to store more water in the stems. Mowing a full-width swath will enhance moisture loss while reducing drying time.After cutting or grazing, it takes approximately 21 to 35 days for the grass to be ready for the next harvest. Factors such as weather, pests, and nitrogen fertilization can influence the rate of regrowth.Summer annual species are susceptible to damage by not only armyworms but also sugarcane aphids, though different species have varying degrees of damage and yield loss.The extent of damage depends on several factors such as aphid density and duration of the infestation period. Most plants are infected following emergence but don’t experience threshold populations until the later growth stages. When deciding which summer annual to use, determine the economics of production, looking at the benefits rather than only costs.Factors to consider include the costs of establishment, grazing strategy, utilization, and water availability. Potential health concerns, such as prussic acid and nitrates associated with grazing certain species, also need to be kept in mind.
Other challenges that are possible with summer annuals are establishment costs, risk of stand failures, and limited growth due to drought.
Kassidy Buse is serving as the 2018 Hay & Forage Grower summer editorial intern. She is from Bridgewater, S.D., and recently graduated from Iowa State University with a degree in animal science. Buse will be attending the University of Nebraska-Lincoln to pursue a master’s degree in ruminant nutrition this fall.