Researchers document animals’ preference for Purdue-patented sorghum technology

A sorghum technology developed at Purdue University improves crop and animal safety. Now research confirms that it appeals to the taste buds of grazing ewes.

Sorghum is a resilient forage crop because it tolerates heat and drought. However, it produces the metabolite dhurrin, which breaks down into hydrogen cyanide, a substance also called prussic acid that is toxic to livestock.

A research team led by Mitch Tuinstra, the Wickersham Chair of Excellence in Agricultural Research and professor of plant breeding and genetics in Purdue’s Department of Agronomy, developed the prussic acid-free sorghum that can ease the minds of farmers concerned about feeding forage sorghum to their animals.

Purdue-based research featured on the June 2024 cover of Crop, Forage & Turfgrass Management shows that the new sorghum technology also improves palatability. Based on differences between pre- and post-grazing forage mass and measurements from drones, the researchers confirmed that ewes not only preferred grazing on the prussic acid-free hybrid over conventional sorghum hybrids, but they also were able to detect and selectively feed on the preferred plants.

The lead author of the article is Tuinstra’s former PhD student Shelby Gruss, now an assistant professor of agronomy and the state forage specialist with Iowa State University Extension and Outreach.

Tuinstra’s research team developed the prussic acid-free sorghum technology in 2001. As primary investigator, Tuinstra disclosed the technology to the Purdue Research Foundation's Office of Technology Commercialization, which applied for and received a patent for it in 2016.

Jay Hulbert, president and CEO of Ag Alumni Seed, was brought in to help explore the technology’s potential commercialization. Hulbert’s company produces high-performance popcorn hybrids, but the nonprofit Purdue affiliate also provides expertise and funding to move Purdue’s value-added crop traits to market.

Planting prussic acid-free sorghum would increase farmers’ ability to manage toxicity risk in livestock when using sorghum forages. “I thought this was a groundbreaking idea,” Hulbert said. “The worst thing in the world for somebody in animal agriculture is to do something that causes harm to their animals. In parts of the U.S. where drought and high temperatures are becoming more and more of a problem, this could enhance the ability of farmers to provide high-quality feed for their livestock.”

Ag Alumni Seed funded efforts to develop and test prototype varieties at Purdue before licensing the technology to S&W Seed Co., where testing is underway on sorghum hybrids that incorporate the trait. Seed will be widely available in 2025, said Scott Staggenborg, sorghum product marketing director at S&W.

On S&W’s test fields, another animal might have given the Purdue researchers an inkling of the ewes’ munching preferences, albeit an unscientific one. Texas jackrabbits found small plots of prussic acid-free sorghum amid S&W’s much larger sorghum fields, and every night they ate the new growth while leaving the traditional sorghum untouched.

“These rabbits traveled 1,000 feet to find this stuff, and then they kept coming back to it,” Staggenborg said. “We recently had a similar experience with Kansas State University researchers. They were bewildered that a plot that looked great one day was ‘disappearing.’ It was jackrabbits again.” He believes their behavior predicted results of the palatability studies that Gruss conducted with sheep.

The prussic acid-free hybrids were shown to perform as well as conventional hybrids, with high forage accumulation and similar nutritive value. “Outside of the fact that it doesn’t have prussic acid, which is dangerous, it is more palatable. As we get ready to bring this to the market, we talk about all these features,” Staggenborg said.

He expects high demand among growers. “We have people that have tried to put in large orders for the past two years,” he said. “We also have customers in Argentina, Uruguay and Brazil who are excited about planting prussic acid-free hybrids.”

S&W will improve the hybrids by adding select insect and disease tolerances. “We’re going to continually add other traits that enhance the value around this one, but the base is going to be prussic acid-free,” Staggenborg said.

While Indiana is not a leader in U.S. sorghum production, Purdue’s role in developing prussic acid-free sorghum has potential impact worldwide, said Tuinstra, who estimates that more than 40 million hectares of sorghum are grown for grain and forage production globally. “Sorghum is No. 5 in the world for cereals,” he said. And given its resilience, future Indiana farmers may well grow more sorghum as the climate warms, he added.

The prussic acid-free sorghum will be showcased at the 75th anniversary celebration of Purdue’s Agronomy Center for Research and Education on Sept. 6, 2024.