In the Texas Panhandle, water shortages are changing what dairy farmers can grow to feed their cows. Some dairies that once planted corn silage on 80% to 90% of their acreage now have enough water to grow it on just 20%.
Sorghum is helping fill the gap, offering a way to produce forage with roughly 30% less water than corn. But making it work in dairy rations has required improvements in how the crop is harvested and processed.
Research led by Juan Piñeiro, Associate Professor and Extension Dairy Specialist at Texas A&M University, is finding new ways to improve sorghum starch digestibility, potentially making it a more practical option for dairies facing tighter water supplies.
“Here in Texas, we have over 80% of the dairy cows of the state in the Panhandle, where we have water scarcity,” Piñeiro says.
Wheat silage, triticale and sorghum are helping dairies make up for the reduced corn silage acreage. Sorghum also offers another option when drought, limited irrigation or crop disease threatens corn production.
Digestibility Has Been a Hurdle
Sorghum is not a new forage option, but getting the most nutritional value from the crop has presented challenges. Two concerns have been fiber digestibility and starch digestibility, both of which influence how well cows use the feed.
“Two of the main barriers that we were seeing for adoption [were] decreased fiber digestibility of sorghum as compared to corn silage and decreased starch digestibility,” Piñeiro says.
Brown midrib (BMR) sorghum has helped address fiber digestibility. The trait lowers lignin content, making the plant’s fiber easier to digest.
“BMR stands for brown midrib,” Piñeiro explains. “It’s a mutation in some sorghum hybrids” resulting in lower lignin and higher fiber digestibility.
A meta-analysis of nine experiments found BMR sorghum silage had fiber digestibility similar to conventional corn silage. Feeding trials also found no differences in dry matter intake or milk production when BMR sorghum silage replaced corn silage, provided diets were properly adjusted.
Starch has been a tougher problem. Sorghum kernels are five to 10 times smaller than corn kernels, making them harder to break open during harvest.
“The grain is five to 10 times smaller,” Piñeiro says. “So, it’s very difficult to break.”
Early research focused on increasing grain size, but conventional corn kernel processors did not improve starch digestibility as expected.
Researchers also explored male-sterile sorghum, which does not develop grain. Without grain formation, the plant retains more sugar in its leaves and stems.
“Because it doesn’t develop grain, starch is very low but sugars are very high,” Piñeiro says. However, the crop’s high moisture at harvest means farmers must wilt it before ensiling to reach the right dry matter.
More recent research has focused on processing grain-producing sorghum more aggressively to make starch more available to rumen microbes. In one experiment, starch degradability after seven hours increased from 25% without kernel processing to 66% with processing after three months of ensiling. Later trials reached the 80% range and, in some cases, the low 90% range.
Processing Technology Improves Starch Availability
In 2023, Piñeiro visited a dairy using specialized kernel-processing technology designed to break sorghum grain more effectively. He was skeptical of claims about how thoroughly the equipment processed the kernels.
After separating processed and intact grain with a Penn State particle separator, researchers estimated only 1% to 2% of kernels remained intact.
The team tested the technology in a forage research setting, with promising results. In one experiment, starch degradability after seven hours of rumen incubation increased from 25% without specialized processing to 66% after processing and three months of ensiling.
Later experiments, with six and nine months of ensiling, reached the 80% range and even the low 90% range after seven hours. For comparison, average seven-hour starch degradability for corn silage is roughly 75% to 80%, according to the laboratory data Piñeiro referenced.
“Being able to reach these levels with sorghum silage is unprecedented,” he says.
The results point to the value of combining aggressive kernel processing with adequate storage time. Piñeiroestimates the return on investment in one experiment at 8-to-1, based on the starch recovered and potential savings from purchasing less dry ground corn. Returns will vary by hybrid, harvest timing, processing quality and the amount of supplemental grain needed in the ration.
However, the technology comes with added harvesting costs. It uses more fuel and can cut kernel processor life to about half of a conventional corn processor.
Piñeiro estimates custom harvesting costs could rise by roughly $1.50 per ton. He also cautions the economics depend on how much additional starch the system makes available and how much purchased grain a dairy can replace.
For dairies considering the technology, potential feed savings need to be weighed against higher harvesting expenses.
Harvest Timing and Hybrid Selection
Processing equipment alone will not make sorghum silage perform well. Hybrid selection, harvest timing and storage all influence starch availability.
Piñeiro recommends targeting the soft-dough stage through early hard dough for grain-producing sorghum. Harvesting too late, when grain reaches physiological maturity and the black layer forms, can reduce starch digestibility because the kernels become harder and more difficult to break down.
Hybrid maturity also influences harvest timing. Plants producing little grain can take longer to dry down, increasing the risk of harvesting too late.
“When you choose a plant and focus only on tonnage,” Piñeiro says, farmers can end up with a tall, late-maturing crop containing little grain and limited starch. “This technology shines when you have more grain.”
He recommends choosing hybrids expected to have at least 30% to 40% of plant weight in the grain head at harvest. Local trial results can help farmers identify hybrids suited to their growing conditions and forage needs.
During harvest, the equipment must be adjusted specifically for sorghum. Piñeiro recommends a kernel processor roll gap of about 1 millimeter, compared with the roughly 2-millimeter setting commonly used for corn.
He also encourages farmers to monitor processing rather than assume custom harvesters are following the requested settings. Wider roll gaps can leave more kernels intact, reducing the benefits of the technology.
Ensiling time is another consideration. Research suggests sorghum should be stored for at least three months, with some hybrids benefiting from six months of storage. During ensiling, microbes can break down proteins surrounding starch granules, improving starch availability when kernels have been adequately processed.
Diversifying Forage Can Reduce Risk
Interest in sorghum is growing as dairies look for ways to produce forage with less irrigation water and reduce dependence on corn.
Piñeiro says about 50 choppers in the U.S. are now using the specialized processing technology, representing an estimated 150,000 dairy cows. Male-sterile sorghum is also being used in diets serving nearly a quarter-million cows, particularly in the Texas Panhandle.
Beyond water availability, diversifying forage production can help protect farms from crop disease. Piñeiro points to corn stunt disease in Argentina, where outbreaks caused production losses of up to 80% in some northern provinces.
“By diversifying your forage production, you are reducing risk,” he says. “I see forage production the same way” as diversifying investments.
Still, sorghum is not a one-size-fits-all replacement for corn silage. Different sorghum types vary widely in height, maturity, grain production, starch content and fiber digestibility. Replacing corn silage also requires ration adjustments, particularly when the sorghum contains less starch.
Forage needs should guide the decision, Piñeiro says. Farmers first need to determine whether the crop will be fed to lactating cows, replacement heifers or dry cows. Available irrigation water and the length of the growing season also influence hybrid selection.
For dairies facing tighter water supplies, sorghum offers another way to build a forage inventory. Getting the most from it requires attention to crop selection, harvest, storage and ration formulation, with additional care around grain processing and digestibility.
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