The transition into lactation is an inflammatory event. Every cow experiences some degree of inflammation after calving, and that response is part of normal physiology.
“These cows are calving, they all have inflammation and we know that a certain amount of inflammation postpartum is physiologically normal,” says Dr. Jessica McArt, associate professor at Cornell University. “The question is when does inflammation become extreme and what is normal?”
That question is becoming increasingly relevant as researchers look beyond whether a cow has a diagnosed disease and toward the broader biological response occurring during the first days after calving.
Inflammation at Two Days in Milk Is Linked to Key Cow Outcomes
McArt and her colleague Jackson Seminara evaluated inflammation in 266 multiparous Holstein cows on four New York dairy farms. They measured haptoglobin and serum amyloid A, both inflammation markers, at 2 days in milk (DIM), then evaluated those measurements against production, health and herd-removal outcomes.
Cows with higher concentrations of the inflammatory markers at 2 DIM were associated with several less favorable outcomes:
- Lower milk production over the first 10 weeks of lactation
- Lower rumination and activity during the early postpartum period
- Greater risk of dyscalcemia
- Greater hazard of herd removal during the first 305 DIM
“The more inflammation we have, the more bad things that happen,” McArt says.
That finding does not necessarily mean that inflammation causes those outcomes. The study was observational and the relationships are associative. Underlying disease, calving difficulty or other factors could contribute to both the inflammatory response and subsequent outcomes.
However, the work does raise the question: Could the inflammatory response provide an early indication of which cows are not adapting as well to the transition?
The Postpartum Inflammation Signal Can Appear Before Clinical Signs
In unpublished work, McArt and colleagues followed 45 cows intensively, collecting blood samples every eight hours alongside milk measurements, rumination, activity, temperature and clinical observations. Statistical analysis separated cows based on their inflammatory response.
“At 2 days in milk, we started to see differences in activity and rumination,” McArt says.
The biological changes extend beyond behavior as inflammation increases.
“They weren’t eating as well. They were mobilizing adipose tissue and we saw that in the milk,” McArt explains.
That makes the timing notable. Two days after calving may be early enough to identify a difference in the cow’s trajectory, while still leaving time to consider whether intervention could change what happens next.
Targeting Calcium Supplementation Based on Inflammatory Status
Another 2026 study adds an important piece to the picture.
Kathryn Bach and colleagues, including McArt, analyzed data from 545 multiparous Holsteins on the same four New York farms that had participated in a randomized trial of delayed oral calcium supplementation. Cows received a 43g calcium bolus at 2 DIM and another at 3 DIM, or no supplementation. They then examined whether the cows’ inflammatory status at 2 DIM changed their response to calcium.
Among cows with higher haptoglobin concentrations at 2 DIM, calcium supplementation was associated with:
- 3.1 kg/day greater milk production among cows in parity 3 or greater
- A greater likelihood of becoming pregnant among parity groups
- A 50% lower rate of herd removal within 150 DIM
Cows with lower inflammatory concentrations generally did not show the same pattern of response to supplementation.
That raises a larger possibility: Could inflammation eventually become a way to identify which cows are most likely to benefit from a particular intervention?
The answer is not ready for the farm today. Although McArt’s group has identified haptoglobin concentrations associated with greater risk in research populations, those values are not yet validated for routine on-farm treatment decisions. More research is needed to determine whether actionable haptoglobin concentrations can help identify cows whose biology warrants a different management approach.
From Inflammation Data to Better Postpartum Decisions
The challenge now is translating the biological signal into something veterinarians and dairy teams can actually use. Blood measurements of haptoglobin and serum amyloid A can identify differences between cows, but routine blood sampling is not necessarily the end goal. The broader opportunity may be combining biomarkers with information already being generated on the farm, including activity, rumination and milk data.
The calcium findings offer an early example of what that might eventually look like. Inflammation at 2 DIM appeared to modify how cows responded to a postpartum intervention, although the findings need to be validated before haptoglobin can be used as a treatment-selection tool.
For veterinarians, that may be the most interesting direction of this research. The value of measuring inflammation will ultimately depend not simply on identifying a cow at greater risk, but on knowing what that information should change: which cows need closer attention, which intervention might help and when to act.
