March 7, 2008

Summer annual grasses often are an important part of many hay and pasture plans.

Sudangrass. Cane. Sorghum-sudan hybrids. Forage sorghum. These summer annuals can produce a lot of forage even under dry growing conditions, but they can be more stemmy and less digestible than many cattle producers may like. Can they be made better? These days the answer is yes.

A natural, genetic trait called "bmr" is being used in more and more varieties and hybrids of summer annual grasses to make them more digestible. This allows cattle to extract more energy from these forages.

"Bmr" stands for "brown mid-rib." It received this name because the mid-rib or vein that runs down the center of each leaf has a brownish tint instead of the normal whitish color typical in other summer annual grasses.

The color of the mid-rib, though, is not what is important. The important characteristic is how the bmr gene affects forage quality. Grasses that have the bmr gene produce less lignin than other 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, more of the fiber can be digested by your cattle, increasing the energy or TDN value of this forage.

The bmr gene has little other effect on these plants, so they respond like non- bmr plants to other management practices, like planting rate, fertilization, and harvest timing.

Bruce Anderson
Extension Forage Specialist