While corn silage is the widely known forage used for cattle in the United States, forage sorghums and sudangrasses are great alternatives because of their rapid growth and drought tolerance. Below are the key characteristics of each forage.
Sudangrasses are known for having fine stems and a vast tiller network, which allows the plant to rapidly regrow and makes it the more ideal forage for late season pastures or dry hay. The rate of regrowth allows for multiple cuts per season under proper management and provides a high quality feed for ruminants when fed at an earlier maturity. There are many varieties of sudangrass that vary in drought and disease tolerance and lignin content that allows a producer to select the variety to best suit their needs.
Being a tall standing plant with succulent stems and small grain heads, forage sorghum is best used as a silage. With a higher fiber content, there is lower digestibility seen in forage sorghum than other summer annuals, but numerous BMR varieties combat this issue. Sorghums mature late in the season and have the ability to yield more dry matter per acre than corn when in non-irrigated, dry regions, however, total digestible nutrients per acre is lower in the sorghum. Studies have shown that typical sorghums have 10-20% lower feeding value than comparable corn silage. Unlike other summer annuals, sorghum should not be grazed as the high moisture plant contains greater levels of prussic acid, which can be fatal in livestock when grazed after a frost or at short regrowth heights.
Hybrid Sorghum x Sudangrass
The hybrid of the two, commonly called sorghum-sudan, is ideal for summer grazing and green chop, but not hay production because of the thicker stem and slower dry down rate than that of straight sudangrass. These hybrids are more stemy than sudangrasses and regrow at a slower rate, but tend to have greater tonnage yield per acre and, of the three annuals, it has the quickest harvest window with first cut being taken at 45 days. When compared to sorghum, the hybrid has lower risk of prussic acid toxicity and a comparable feed out value, but nutritive value is lower than that of sudangrass and cattle can see a slump in production due to lower energy content.
Written by: Kara Riccioni, MBA, MS, PAS – Forage & Grain Nutrition Specialist