Annual Crops for Forage: Summer-Annual Grasses
Silages made from sorghum contain more digestible energy than legume and cool-season grass silages, and are, therefore, considered high-energy silage crops. Making high-quality silage from sorghum generally is considered easier than it is from forage legumes because of high amounts of nonstructural carbohydrates, which enhance fermentation. The high-energy, low-protein characteristics of sorghum silage make it a good supplement for high-protein forage legumes.
Under adequate growing conditions, the yield of digestible nutrients per acre of forage sorghum is about 92 percent that of corn. The feeding value of sorghum silage generally is considered to be about 85 percent that of corn silage. Therefore, corn silage usually is the preferred high-energy silage grown in Pennsylvania. However, research has shown that fewer deer feed on sorghum than on corn. In addition, in light-textured, shallow soils with a higher risk of drought, growing a certain percentage of the total high-energy silage acreage in sorghum may be a way to hedge against this risk.
There is always a risk of prussic acid poisoning in animals grazing sudangrass; however, newer varieties produce low levels of prussic acid and greatly reduce any risk. In addition to using low prussic acid varieties, do not graze sudangrass until it is at least 20 to 24 inches tall or during or immediately after a drought stress.
Brown midrib (BMR) varieties of sudangrass are available and have higher feeding value than non-BMR varieties. Seed of newer varieties may be difficult to locate but can be found with some searching.
Sudangrass hybrids. Made by crossing different lines or varieties of sudangrass. In general, hybrids have slightly higher yields and are slightly higher in prussic acid than Piper at comparable growth stages.
Sorghum x Sudangrass Hybrids
Made by crossing different lines and varieties of sorghum with lines and varieties of sudangrass. In general, these hybrids have yielded more but are coarser stemmed and higher in prussic acid at comparable growth stages than either Piper or sudangrass hybrids. They appear to have the greatest potential when used for green-chop. For pasture, they are only slightly more productive than Piper, and in early stages of growth they have a higher prussic acid content. When cut at the normal stage for ensiling (at or after heading), they are inferior to corn in quality.