Decoding the dairy dilemma of heat stress

Collaborating with Joseph McFadden, associate professor of dairy cattle biology, Duan and her research team — including graduate students Guangsheng Li and Xingtan (Vera) Yu — examined the impact of heat stress on gene expression in cow livers. 

Their research found that heat stress in cows triggers increased levels of heat shock proteins and decreased activity of mitochondrial genes in their livers. Interestingly, their analysis showed that reduced food intake explains only 30–50% of the drop in milk production during periods of heat stress. This suggests that elevated temperatures directly impact cow metabolism and inflammatory responses—which further affects milk production, such as milk protein synthesis, milk content and yield, Duan said.

To conduct in vitro studies examining heat stress responses at the cellular level, Duan collaborated with Dr. Gerlinde Van de Walle, Alfred H. Caspary Professor at Cornell’s College of Veterinary Medicine. Together, they investigated the effects of heat stress on milk protein production in bovine mammary cells. Specifically, their study examined how heat stress alters gene expression and the recovery process in mammary cells of dairy cows. 

The researchers discovered that heat stress suppresses genes involved in milk lipid synthesis and cellular differentiation while activating heat shock proteins to manage stress. During the recovery phase, genes associated with protein repair and cellular balance become more active. These findings shed light on the molecular mechanisms of heat stress and could help improve how dairy cattle cope with it, Duan explained.

By combining insights from both studies, Duan is building a more comprehensive understanding of how heat stress impacts dairy cows at multiple biological levels. “We're seeing common themes emerge,” she noted. “For example, the upregulation of heat shock proteins and the disruption of cellular metabolism appear to be consistent responses to heat stress, whether we're looking at liver cells in dairy cows or mammary cells in culture.”

As research progresses, Duan’s goal is to translate these scientific insights into practical strategies for mitigating heat stress in dairy production. Potential applications could include nutritional interventions, breeding strategies for heat tolerance, refined cooling practices and even pharmaceutical interventions.

“This isn't a problem that can be solved by any one discipline alone. We need insights from functional genomics, animal science, climate science and agricultural economics to develop comprehensive solutions.”         

Duan's work exemplifies the power of collaborative, interdisciplinary research in addressing complex challenges like climate change impacts on agriculture. “This isn't a problem that can be solved by any one discipline alone,” she said. “We need insights from functional genomics, animal science, climate science and agricultural economics to develop comprehensive solutions.”       

As global temperatures continue to rise, Duan's research takes on increasing urgency. Climate projections suggest that by 2045, many major agricultural regions will face extreme heat stress risks. 

“It’s an immense challenge,” she said. “But I'm optimistic that with continued research and collaboration, we can develop effective strategies to help dairy cows—and the entire dairy industry—adapt to a warming world.”

Caroline Stamm ’24 is a communications assistant for the Cornell CALS Department of Animal Science.