Brown midrib
sorghum
good dairy diet option
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Corn silage is golden in dairy cow diets, but a sorghum newcomer could vie for the crown. That newcomer is brown midrib forage sorghum. Recent University of Nebraska animal science research shows cows fed brown midrib sorghum silage produce 10 more pounds of milk per day than cows fed regular sorghum silage and the same amount as those fed corn silage. "Brown midrib forage sorghum clearly outperforms standard sorghum hybrids and may be equal to some corn hybrids," Dairy Scientist Rick Grant said. "Brown midrib sorghum has the potential to replace corn silage under conditions where forage sorghum is the more agronomically suited crop." Brown midrib sorghum refers to the brown center of the plant stalk that normally is green or yellow-white. Brown midrib is a genetic mutation that reduces the amount of lignin in the stalk. The mutation was discovered in the 1920s at the University of Minnesota, but hybrids with improved yields and less stalk lodging were only recently developed. Sorghum is a cheaper feed than corn. It requires less fertilizer, less insect control and one-third less water. Sorghum has long been known as a "rescue crop," Grant said. It can be planted later in the season - for example, when another crop has failed - and still provide a crop. Despite these advantages, traditional sorghum is less digestible than corn, Grant said. Traditional sorghum has 30 percent to 40 percent more lignin, or what Grant calls "plant plastic," than corn. Lignin inhibits fiber digestibility, which reduces milk production. Brown midrib sorghum silage has 17 percent less lignin than regular sorghum silage, which makes it more digestible. Five years of Institute of Agriculture and Natural Resources research showed brown midrib sorghum is 10 percent more digestible than regular sorghum. That translated into 10 more pounds of milk per day, Grant said, which means brown midrib could be worth $200 an acre more than regular sorghum. Cows fed brown midrib sorghum produced an average of 75 pounds of milk per day in 15-week trials. Cows eating the cheaper brown midrib sorghum silage produced the equivalent quantity of milk with similar quality as those eating corn silage. Palatability and feed intake also were comparable to corn silage diets, Grant said. Cows in the long-term study were fed 17.5 percent alfalfa silage; 35.3 percent test brown midrib, regular sorghum or corn silage; and 47.2 percent concentrate of ground corn, soybean meal, whole cottonseed, vitamins and minerals. Brown midrib outperforms regular sorghum in dairy cow diets, Grant said, but what increases its digestibility may reduce its agronomic strength. Lignin strengthens the stalk, he said, so brown midrib sorghum may lodge more than corn or regular sorghum. Ongoing research should answer this question, Grant said. Both regular sorghum and brown midrib average 25 to 30 tons per acre of silage, Grant said. From 1994-1997, anywhere from 810,000 to 1.25 million acres of forage sorghum were harvested in Nebraska annually. About 40 percent of Nebraska producers feed some forage sorghum, he said. Because sorghum grows well under dry conditions, brown midrib potentially could replace corn for dairy feed in drier parts of the country. Some brown midrib is grown in Nebraska, but more is grown in Texas and Kansas. Grant suggests producers interested in brown midrib plant a portion of their acres to the new sorghum to see how it fares in their fields. Brown midrib did well in trials, but Grant noted real field conditions are hard to duplicate. Garrison & Townsend Inc. of Hereford, Texas, provided funding and sorghum seed for this research. - Cheryl Alberts |
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