At the Purdue University Animal Science Research and Education Center, ewes preferentially eat dhurrin-free sorghum hybrids. (Photo by Purdue Agriculture Communications)
WEST LAFAYETTE, Ind. — A sorghum technology developed at Purdue University improves crop and animal safety, and new research confirms it appeals to the palate of grazing ewes.
Sorghum is a resilient forage crop because it can tolerate heat and drought, but it produces a metabolic product, dhurrin, which breaks down into hydrogen cyanide, also known as prussic acid, which is toxic to livestock.
A research team led by Mitch Tuinstra, Wickersham Distinguished Professor of Agricultural Research and professor of plant breeding and genetics in the Purdue College of Agriculture, has developed a cyanide-free sorghum that could ease concerns for farmers worried about feeding sorghum to their livestock.
A Purdue University study featured on the cover of the June 2024 issue of Crop, Forage & Turfgrass Management shows the new sorghum technology also improves eating quality. Based on pre- and post-grazing forage volume differences and drone measurements, researchers determined that ewes not only preferred the cyanide-free sorghum hybrid over a traditional sorghum hybrid, but they were also able to sense and selectively eat their preferred plants.
The lead author of the article is Shelby Glass, a former Tuinstra doctoral student who is now an assistant professor of agronomy and state forage specialist for the Extension Service at Iowa State University.
Tuinstra's research team developed the cyanide-free sorghum technology in 2001. As principal investigator, Tuinstra disclosed the technology to the Purdue Research Foundation's Office of Technology Commercialization, which applied for and received a patent for the technology in 2016.
Jay Halbert, president and CEO of Ag Alumni Seed, was brought in to explore the technology's commercialization potential. While Halbert's company produces high-performance popcorn hybrids, the nonprofit Purdue affiliate is also providing expertise and funding to bring Purdue's value-added crop traits to market.
Planting cyanide-free sorghum would increase farmers' ability to manage toxicity risks when feeding sorghum to livestock. “We thought this was a revolutionary idea,” Halbert says. “The last thing anybody in the livestock industry would want to do is do something that harms their animals. In parts of the U.S. where drought and high temperatures are becoming more and more of a problem, this could increase farmers' ability to provide high-quality feed for their livestock.”
Ag Alumni Seed funded an effort to develop and test prototype varieties at Purdue University, then licensed the technology to S&W Seed, which is currently testing sorghum hybrids incorporating the trait. The seeds will be widely available in 2025, said Scott Staggenborg, S&W's director of sorghum product marketing.
At S&W's test fields, another animal may have given the Purdue researchers a nonscientific clue about the ewes' feeding preferences: Texas jackrabbits found a small patch of cyanide-free sorghum in S&W's much larger sorghum field and ate the shoots each night, leaving the conventional sorghum untouched.
“The rabbits would walk 1,000 feet to find it and then come back,” Staggenborg says. “We had a similar experience recently with researchers at Kansas State University who were puzzled when a patch that looked great one day just 'disappeared.' It was a jackrabbit again.” He thinks the rabbits' behavior predicted the results of Groos's palatability study with sheep.
The cyanide-free hybrids stored more feed and performed just as well as the conventional hybrids in terms of nutritional value. “They're more palatable, except they don't contain the dangerous cyanide,” Staggenborg said. “We'll be discussing those attributes as we get them ready to go to market.”
He expects demand to increase among growers. “We've had people try to place large orders for the past two years,” he says. “We also have customers in Argentina, Uruguay and Brazil who are keen to grow hydrocyanic acid-free hybrids.”
S&W plans to improve the hybrid by imparting select pest and disease resistance. “We will continue to add other traits that will increase the value of the variety, but the base will be prussic acid-free,” Staggenborg said.
While Indiana is not a leader in U.S. sorghum production, Perdue's role in developing cyanide-free sorghum could have global implications, Tuinstra said. He estimates that more than 40 million hectares of sorghum are grown worldwide for grain and feed production. “Sorghum is No. 5 in grain production,” he said. And given its resilience, Indiana farmers may grow more sorghum in the future as the climate warms, he added.
The cyanide-free sorghum will be showcased at the Purdue University Agricultural Research and Education Center's 75th anniversary celebration on Sept. 6, 2024.
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