Ketosis in cattle is a metabolic disorder where a cow’s body breaks down too much stored fat too quickly, flooding the bloodstream with compounds called ketone bodies. It strikes dairy cows most often in the first few weeks after calving, when the energy demands of milk production outpace what the cow can take in through feed. The result is a cascade of problems: dropped appetite, falling milk output, and in severe cases, neurological symptoms.
Why Ketosis Happens
The root cause is an energy gap. In early lactation, a dairy cow needs enormous amounts of energy to produce milk, but her feed intake hasn’t caught up yet. This mismatch is called negative energy balance. To close the gap, the cow mobilizes her own body fat reserves as fuel. That fat mobilization is normal to a degree, but when it happens too fast or too extensively, the liver can’t process all the incoming fatty acids through its usual energy pathways. Instead, it converts them into ketone bodies, which accumulate in the blood, milk, and urine.
Cows in negative energy balance have lower blood glucose, lower insulin, and higher concentrations of free fatty acids and the ketone body BHB (beta-hydroxybutyrate). When the liver becomes overwhelmed with fat, it can also develop fatty infiltration, compounding the problem and making it harder for the cow to recover on her own.
Type I vs. Type II Ketosis
Not all ketosis looks the same. The two recognized forms differ in timing, cause, and the type of cow they tend to affect.
Type I (classical ketosis) is the more straightforward version. It shows up between 20 and 50 days after calving in cows that were producing a lot of milk before symptoms appeared. The cow simply can’t eat enough to keep up with her milk output, so blood glucose drops and fat mobilization ramps up. Herds fed component rations (grain and forage offered separately) see it more often.
Type II ketosis hits earlier, typically within the first 5 to 21 days after calving. It’s driven less by high production and more by poor feed intake during the dry period or immediately after birth. These cows often arrive at calving overconditioned, carrying too much body fat. That excess fat infiltrates the liver, which then struggles to process nutrients normally. Unlike Type I cows, Type II cows usually aren’t high producers, and they may have elevated stress hormones and transiently high blood glucose and insulin levels rather than the straightforward low-glucose pattern of Type I.
Signs to Watch For
Ketosis symptoms are notoriously vague in the early stages, which is part of what makes the condition tricky to catch. The most consistent early sign is reduced feed intake. If cows are offered grain and forage separately, a ketotic cow will typically refuse grain first while still picking at hay or silage. In group-fed herds where you can’t easily monitor individual intake, the first things you’ll notice are lower milk production, lethargy, and a gaunt or empty-looking abdomen.
As the condition progresses, signs become more obvious:
- Rapid, visible loss of body condition
- Firm, dry manure
- A distinct acetone smell (like nail polish remover) on the cow’s breath and in her urine
- Mild dehydration
A small percentage of cows develop what’s called nervous ketosis, which produces more dramatic symptoms: compulsive licking of objects or themselves, an unsteady gait, bellowing, pica (eating non-food items), and occasionally aggression. On physical exam, body temperature is usually normal and rumen activity varies from cow to cow, making ketosis easy to confuse with other fresh-cow problems.
How Ketosis Is Diagnosed
The gold standard is measuring BHB in a blood sample. A blood BHB concentration at or above 1,400 µmol/L (1.4 mmol/L) is the widely used threshold for subclinical ketosis, meaning the cow’s ketone levels are elevated even if she looks fine.
Cow-side tests vary considerably in accuracy. A study comparing three common options found that urine test strips (measuring acetoacetate) performed well at the “trace” reading, catching 90% of truly ketotic cows while correctly ruling out 86% of healthy ones. Milk test strips at their lowest cutoff caught 88% of cases with 90% accuracy on negatives. Milk powder tests, on the other hand, were highly specific (99%) but missed more than half of positive cases, making them poor screening tools.
The practical takeaway: if you’re screening fresh cows routinely, blood BHB meters designed for cow-side use give the most reliable results. Urine strips are a decent alternative when blood testing isn’t practical, but milk powder tests alone will miss too many subclinical cases to be useful for herd monitoring.
Treatment and Recovery
The goal of treatment is simple: get glucose into the cow and slow down fat mobilization. The two mainstays are intravenous glucose, which provides an immediate but short-lived energy boost, and oral propylene glycol, which the cow’s liver converts into glucose over several hours. Propylene glycol is typically given as an oral drench of about 500 mL per dose, repeated over multiple days. One protocol studied in transition cows used six doses of 500 mL spread across the first nine days after calving, while a lighter protocol used three doses on calving day, day 7, and day 14.
Most cows with Type I ketosis respond well to treatment within a few days. Appetite returns, milk production climbs back up, and ketone levels normalize. Type II ketosis is harder to manage because the underlying liver damage takes longer to resolve. These cows may need repeated treatments and closer monitoring, and some never fully recover their production potential for that lactation.
Complications Beyond Ketosis Itself
Ketosis rarely exists in isolation. The same negative energy balance that triggers it also suppresses immune function and disrupts reproductive hormones. Cows with ketosis are at significantly higher risk for displaced abomasum (twisted stomach), uterine infections, mastitis, and poor fertility. Fatty liver, which both contributes to and results from severe ketosis, can become a serious condition in its own right, reducing the liver’s ability to clear toxins and produce the proteins needed for immune defense. Addressing ketosis early doesn’t just restore milk production; it reduces the odds of these costly secondary problems.
What Ketosis Costs
A systematic review of 10 studies found that the estimated cost per case of ketosis ranges enormously, from roughly €19 to €812, depending on severity, how it’s defined, local milk prices, and whether secondary diseases are factored in. At the farm level, estimates land between €3.60 and €29 per cow per year across the herd. The wide range reflects differences in herd size, production level, and how aggressively farms monitor and treat fresh cows. Even at the low end, subclinical ketosis adds up quickly in a large herd because it’s common and often undetected.
Prevention Strategies
Preventing ketosis starts well before calving. The single most important factor is body condition at the time of calving. Research consistently points to an optimal body condition score between 3.0 and 3.5 (on a 5-point scale). Cows that calve above 3.5 are at higher risk because they tend to eat less after calving and mobilize fat more aggressively. Keeping cows from getting overconditioned during the dry period is one of the most effective and lowest-cost prevention tools available.
Nutritional management during the transition period (roughly three weeks before through three weeks after calving) is the other major lever. A well-formulated total mixed ration that maximizes dry matter intake in the weeks after calving helps close the energy gap before it becomes dangerous. Some herds add glucogenic supplements like rumen-protected glucose to the postpartum diet to give cows an extra energy source during the critical window.
Propylene glycol given preventively as an oral drench around calving has been shown to reduce ketosis incidence in high-risk herds. Feed additives that improve rumen efficiency can also help by squeezing more energy out of every pound of feed the cow does eat. The most effective prevention programs combine body condition management in the dry period with aggressive feed bunk management and targeted supplementation after calving, rather than relying on any single intervention.