CLEAR Conversations: Dr. Kelly Nichols on the Power of Protein, Nitrogen, and the Dairy Cow
When Dr. Kelly Nichols talks about dairy cows, you can hear the enthusiasm in her voice. As an assistant professor in the UC Davis Department of Animal Science, Nichols is part of a group of researchers who are looking at one of the most complex challenges in livestock production: how to feed cows in ways that support productivity, animal health, and environmental stewardship.
Nichols recently joined host Tracy Sellers on the Clear Conversations podcast to share her journey and talk about her work. Their discussion ranged from nitrogen cycling to gut-brain signaling, offering a glimpse into a world of nutrition research that’s far more intricate—and far more important—than most people might realize.
Nichols didn’t grow up around dairy cows. “I actually grew up on a horse farm in Canada,” she explained. “I thought I was going to be a veterinarian.” Everything changed when she began working in a dairy nutrition and metabolism lab during her undergraduate studies at the University of Guelph.
There, she found what she calls her scientific home: ruminant metabolism.
“I really fell in love with how nutrition shapes every metabolic pathway—especially in lactating cows, whose physiology is incredibly dynamic,” she said.
After a master’s at Guelph, Nichols moved to the Netherlands to pursue her Ph.D. at Wageningen University—“the UC Davis of Europe,” as she describes it. She stayed for a decade, delving deeper into dairy nutrition and later serving on the ruminant research team at Trouw Nutrition.
Her time in Europe shaped her understanding of the environmental pressures surrounding livestock systems. Dense animal populations, limited land, strict nutrient regulations, and intense public scrutiny made nitrogen management a central challenge.
“The Netherlands is a tiny country with a lot of livestock,” Nichols said. “And when nutrients like nitrogen exceed what the land can manage you get impacts on the environment.”
From new nitrogen limits to farmer protests, she witnessed firsthand how complex—and contentious—these issues can be.
Methane Gets the Headlines, but Nitrogen Holds the Questions
Now at UC Davis, Nichols is bringing her expertise to California at a moment when the state is a global leader in methane reductions. But as she shared at the UC Davis State of the Science Summit last year, methane is only part of the story.
“I’m heavily biased,” she laughed, “but nitrogen is a much more difficult problem. It touches so many systems in the cow’s body, and there will never be a simple inhibitor the way there is for methane.”
Protein metabolism, she explained, is at the heart of nitrogen use. And because protein fuels so many essential processes—milk production, growth, reproduction, immune function—finding the right balance is a constantly moving target.
That big-picture awareness was the inspiration behind her Summit talk with colleague Dr. Maggie Gill. Their message was simple: you can’t reduce one environmental impact without understanding the ripple effects.
“The Cow as an Orchestra”
One of the most memorable metaphors from the Summit came courtesy of Gill: the cow’s brain as an orchestra conductor, coordinating dozens of systems—digestive, neurological, metabolic—into a complex symphony.
Nichols said the comparison struck a chord because researchers still know so little about how these systems communicate.
“In humans, gut-brain axis has been a huge talking point,” Sellers noted. “But in livestock, especially ruminants, we know very little.” She then asked Nichols why that is?
“It got a lot of people thinking,” Nichols said. “Who knows where that research could lead?”
Given the rumen’s unique microbial ecosystem, understanding those gut-brain interactions may be crucial as scientists develop new approaches to nutrition and environmental sustainability.
Nitrogen Research at UC Davis
Nichols is currently launching her first major study at UC Davis, focusing on a process called urea recycling. It’s a mechanism that allows ruminants to repurpose nitrogen that would otherwise be lost in urine—turning it into microbial protein that the cow can use again.
“We know quite a lot about this process in growing cattle,” she said. “But almost nothing about how it works in lactating cows, whose nutritional demands are very different.”
To study this, Nichols and her team will work with eight cannulated cows, allowing researchers to precisely infuse different protein sources into different parts of the digestive tract. By tracking what goes in, what comes out, and how the cow’s metabolism responds, they hope to uncover how to redirect more nitrogen away from excretion and toward productive use.
“It’s fundamental research,” Nichols said, “but the applications are direct. Nutritionists already think in terms of protein sources, not just protein levels. This will help refine those decisions.”
Even with decades of research behind the field, Nichols says the questions ahead of dairy nutrition scientists are bigger—and more exciting—than ever.
Two of the areas she hopes to tackle in the coming years include understanding exactly which amino acids are available for absorption in ruminant animals and exploring how early-life nutrition affects nitrogen efficiency later in life
“What we feed calves could shape how they use nitrogen as adults,” she said. “That’s a huge, mostly unexplored frontier.”
Why California Is the Right Place for This Work
Nichols said UC Davis—and the Clear Center—are uniquely positioned to lead on nitrogen the way the state has led on methane.
“Dr. Mitloehner told me during my interview that nitrogen would become a major issue here,” she recalled. “And he was right.”
For Nichols, joining UC Davis was a chance to bring her experience from the Netherlands to a state where research can quickly translate into practice.
“There’s a strong track record here,” she said. “What happens in California influences the industry across the country.”
As the conversation wrapped up, one thing became clear: the future of sustainable dairy farming depends on understanding systems that many people haven’t really studied as much.
And Dr. Kelly Nichols is eager to help change that.
“There’s so much still to learn,” she said. “And that’s what makes this research exciting.”