Dry-off is one of the most important transitions in a dairy cow’s production cycle, yet there are relatively few ways to assess what is happening inside the mammary gland once milking stops. While milk yield, udder appearance and clinical outcomes provide useful clues, they offer only an indirect view of the biological changes occurring within the gland itself.
This challenge has prompted researchers at the University of Wisconsin-Madison to explore whether mammary ultrasound can provide a practical, on-farm method for monitoring involution. The research is led in part by Laura Hernandez, professor of lactation biology, whose laboratory has spent years developing ultrasound techniques to evaluate mammary growth and development.
According to Hernandez, interest in the technology stemmed from the difficulty of evaluating dry-off success without repeatedly collecting milk samples.
“One of the endpoints is ‘Did milk production go down?’ and you don’t want to keep milking the cow if that’s what you’re trying to do,” she says.
Why Dry-Off Remains Difficult to Measure
The biological process of involution begins as milk secretion slows and the mammary tissue starts remodeling in preparation for the next lactation. During this period, cellular junctions change, immune activity increases and the gland undergoes significant structural transformation. Monitoring those changes can be challenging. Once cows are dried off, many of the traditional measurements used to evaluate mammary function are no longer practical to collect.
Animals that continue producing large volumes of milk late into lactation can be difficult to dry off effectively, raising concerns about mammary health, dry period success and downstream effects on colostrum quality and calf health. Hernandez suggests that solutions may need to begin well before dry-off day through nutritional and management strategies designed to gradually reduce production during late lactation.
Looking Inside the Mammary Gland
The current project builds on approximately seven years of work developing and validating mammary ultrasound techniques.
Hernandez has been investigating whether ultrasound can reliably track mammary growth, development and production potential. The project combines ultrasound imaging with mammary tissue biopsies and histological analysis. By comparing what appears on an ultrasound image with actual tissue characteristics under the microscope, researchers hope to identify specific imaging features that correspond with the structural changes known to occur during involution.
Early Findings Suggest Potential Dry-Off Indicators
Although the work remains in its early stages, a pilot study has been completed and several areas of interest have been identified.
“One of the ones that looks promising is the gland cistern. The size, and potentially area, of that could be indicative of a faster dry off,” Hernandez says.
The gland cistern is the main internal holding reservoir located just above the teat. This is one potential ultrasound feature that could be linked to measurable biological changes inside the gland.
Hernandez says the gland cistern observations appear to align with histological characteristics typically associated with a drying-off mammary gland. A larger study beginning this summer will determine whether those early observations consistently predict involution success.
Supporting Antimicrobial Stewardship Goals
This project also touches on a broader issue facing dairy veterinarians: reducing antimicrobial use while maintaining udder health.
As selective dry cow therapy becomes more widely adopted, practitioners are increasingly interested in management strategies that support a successful dry period while minimizing unnecessary antimicrobial treatments. Better understanding of involution could help veterinarians identify cows at risk of dry-off problems and make more informed recommendations about intervention strategies.
Hernandez believes improved involution management could contribute to those goals.
“We’re really excited about it, and excited in general, that there is this opportunity that we could reduce antimicrobial usage and antibiotic usage in these animals,” she says.
Reducing antimicrobial use would benefit both animal and human health, making the work relevant beyond individual dairy operations.
Biomarkers and Artificial Intelligence Could Expand Future Applications
Hernandez’s team is also examining biological markers that may help explain what is happening inside the mammary gland during dry-off.
Future studies will measure milk sodium and potassium concentrations, blood lactose levels and other indicators associated with changes in mammary epithelial tight junctions. Together, these measurements could provide a more complete picture of the involution process and help validate what they are seeing on ultrasound images.
At the same time, the team is developing artificial intelligence systems capable of interpreting mammary ultrasound images automatically. Years of image annotation and validation work have created a dataset linking ultrasound features to confirmed tissue characteristics, providing the foundation for future automated image analysis.
A New Window into Dry-Off Biology
If the approach proves successful, veterinarians may eventually have a way to monitor involution more directly rather than relying solely on production records and clinical observations.
For Hernandez, one of the most exciting aspects of the research is the possibility of turning ultrasound into a practical tool for understanding mammary biology in real-world settings.
“It’s all just shades of gray,” she says. “But it is amazing looking at those shades of gray on an ultrasound. It’s really incredible. I think we have a lot of potential here to make this useful.”
