Sudangrass, cane, sorghum-sudan hybrids and forage sorghum all can produce good forage yields even under dry growing conditions. These forages, however, historically have tended to be more stemmy and less digestible than cattle producers like.
To counter this, many new varieties and hybrids of summer annual grasses have been bred to include a natural, genetic trait called "bmr" to make them more digestible and palatable, enabling cattle to extract more energy from the forage. "Bmr" stands for "brown mid-rib." Plants carrying this characteristic have a brownish mid rib rather than the more typical whitish one.
The color of the mid-rib, though, is not what is important. The important characteristic is how the bmr gene affects forage quality. Grasses with this gene produce less lignin than normal plants. Lignin is a complex compound that can attach to fiber components like cellulose in the plant and make it less digestible. Since plants with the bmr gene produce less lignin, cattle can digest more of the fiber, increasing the energy or TDN value of this forage.
The bmr gene has little other affect on these plants, so they respond similarly to non bmr plants to planting rate, fertilization and harvest timing.
Bruce Anderson
Extension Forage Specialist
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