Do You Know Your Blind Spot?
Subclinical Ketosis: an Invisible Disease with Very Real Consequences
An interview with Angela Kinney, DVM, Staff Veterinarian at BouMatic
In dairy herds, some diseases go unnoticed… while still having a major impact on herd performance. This is particularly true for subclinical ketosis—a common metabolic disorder that is difficult to detect. We consult Angela Kinney, DVM Staff Veterianarian at BouMatic to get more insight.
Can you explain what this disease is?
Angela Kinney, DVM: Subclinical ketosis is a common metabolic disorder that usually occurs at the beginning of lactation, in the weeks following calving. During this period, a cow produces large amounts of milk, which drastically increases her energy requirements. If the energy provided by the ration does not meet those needs, the cow enters a negative energy balance. To compensate, she mobilizes her body fat reserves, which leads to the production of ketone bodies. Biologically speaking, when the level of beta-hydroxybutyrate, or BHB, exceeds 1.2 mmol/L, the cow is considered to be in subclinical ketosis. Unlike clinical ketosis, the signs are very subtle or even completely absent, so the cow often looks healthy, making detection extremely difficult.
How common is subclinical ketosis in dairy herds?
Angela Kinney, DVM: It’s much more common than many people realize. On average, subclinical ketosis affects between 10 and 25 percent of cows in dairy herds, and in early lactation those levels can reach up to 40 percent. That means in many herds, one out of every four cows may be affected without anyone noticing it in daily management.
If there are no obvious symptoms, why should producers be concerned about it?
Angela Kinney, DVM: Even without visible symptoms, the consequences are very real and measurable. From a production standpoint, a cow in negative energy balance can produce up to two kilograms less milk per day. Over an entire lactation, that can add up to roughly 300 kilograms of milk that are simply lost.
And what about impacts on health?
Angela Kinney, DVM: Subclinical ketosis significantly weakens the cow and greatly increases the risk of other diseases. Research shows that the risk of a displaced abomasum is multiplied by eleven, metritis by four, mastitis by seven, clinical ketosis by fourteen, and lameness by two. These secondary health issues often end up being what producers notice, while the underlying metabolic problem remains hidden.
Does it also affect reproduction?
Angela Kinney, DVM: Absolutely. Reproductive performance is clearly impacted. We see a decrease in insemination success rates of up to 35 percent, and the interval before conception can be extended by around 22 days. That has obvious implications for herd efficiency and profitability.
Speaking of profitability, what is the economic impact of subclinical ketosis?
Angela Kinney, DVM: Scientific research has shown that subclinical ketosis can cost up to €262 per affected cow. In fact, the total cost can be even higher than the cost associated with mastitis. One recent global analysis indicated that subclinical ketosis ranks as the number one disease worldwide in terms of annual losses, accounting for approximately 18 billion US dollars each year. At the herd level, these losses accumulate very quickly, especially because they’re often invisible at first glance.
Why is detection still such a challenge on farms today?
Angela Kinney, DVM: The biggest challenge is that subclinical ketosis is essentially a silent disease. Without clear clinical signs, it can go completely unnoticed unless specific monitoring tools are used. Traditional methods like blood or urine tests are only snapshots in time and can be labor-intensive. They don’t allow for continuous, whole-herd monitoring.
How can producers prevent or correct subclinical ketosis?
Angela Kinney, DVM: Prevention starts with strong nutritional management, especially during the transition period. High dry matter intake is absolutely critical, because it largely determines whether a cow’s energy requirements are met. That means ensuring sufficient dry matter and energy intake, balancing rations according to the stage of lactation, monitoring body condition, and when needed, using energy supplements like propylene glycol. Dry matter intake at the end of the dry period is especially decisive—it strongly influences intake at the beginning of lactation. The higher the intake during the dry period, the lower the risk and severity of negative energy balance after calving, and therefore the lower the risk of subclinical ketosis. Early detection is still essential so that interventions can happen before serious consequences develop.
BouMatic is working on new solutions in this area. Can you tell us more about that?
Angela Kinney, DVM: Today we have technologies that allow us to go much further than before. BouMatic’s MilkGenius system analyzes milk in real time during milking and can detect signs of energy deficiency at a very early stage. This makes it possible to take immediate action and even automatically adjust feeding strategies. With this kind of real-time monitoring, producers no longer have to wait for visible symptoms to appear. It’s a powerful step forward in effectively preventing subclinical ketosis and protecting herd performance.
References: Liang et al., 2017; McArt et al., 2015; Rasmussen et al., 2024