Ketosis in cattle is a metabolic disorder where a cow’s body breaks down its own fat for energy faster than the liver can process it, flooding the bloodstream with acidic compounds called ketone bodies. It occurs almost exclusively in dairy cows during the weeks surrounding calving, when the energy demands of milk production outstrip what the cow can take in through feed. The condition ranges from a silent, subclinical form that quietly drains milk yield to a full clinical disease with visible neurological symptoms.
Why Ketosis Happens After Calving
A dairy cow’s energy needs spike dramatically once she begins producing milk. In the first weeks of lactation, most high-producing cows simply cannot eat enough to keep up. The gap between what she burns and what she consumes is called negative energy balance, and every fresh cow experiences it to some degree. In a healthy transition, the cow draws moderately on her fat reserves to bridge that gap, and her liver converts those fats into usable fuel.
When the energy deficit is too large, or when the liver is already compromised, the system breaks down. Fat floods into the liver faster than it can be fully converted to glucose. Instead, the liver produces ketone bodies as a byproduct of incomplete fat metabolism. Small amounts of ketones are normal and harmless, but when they accumulate in the blood, they suppress appetite further, creating a downward spiral: the cow eats less, mobilizes more fat, and produces even more ketones.
Type I vs. Type II Ketosis
Not all ketosis looks the same. The two recognized forms have different timing, different underlying causes, and different responses to treatment.
Type I (classic or nutritional ketosis) shows up 2 to 6 weeks after calving, right around peak milk yield. It is driven purely by negative energy balance. The cow’s blood sugar drops because her liver cannot produce glucose fast enough, and ketone levels rise to compensate. This is the more straightforward form, and it typically responds well to treatments that restore blood glucose.
Type II (fatty liver ketosis) appears earlier, within the first 1 to 2 weeks after calving. Rather than a simple energy gap, this form involves excessive fat buildup in the liver and impaired liver function. Cows with Type II ketosis often show signs of insulin resistance: blood sugar may actually be normal or even elevated, but the liver is too overwhelmed with fat to function properly. These cows tend to be overconditioned at calving, meaning they carried too much body fat into the dry period. Type II is harder to treat because the problem is not just a lack of glucose but a deeper metabolic and hormonal disruption.
Subclinical Ketosis: The Hidden Problem
The majority of ketosis cases on a dairy farm are subclinical, meaning the cow shows no obvious signs of illness. She still eats, still milks, and still moves through the parlor. But her ketone levels are elevated enough to cause real damage. Subclinical ketosis during the first week of lactation can reduce milk yield by about 2.5 kg per day, and affected cows are roughly three times more likely to be culled from the herd. Over an entire lactation, milk losses can exceed 300 kg per cow.
The financial toll adds up quickly. Estimates for the cost of a single subclinical case range from about $77 to $289 in the United States, with similar figures reported in Canada and Europe. Those numbers account for lost milk, treatment, reduced fertility, and increased risk of secondary diseases. One of the most expensive complications is displaced abomasum, which averages around $650 per case on its own. Subclinical ketosis also raises the risk of mastitis and reproductive problems, which often show up as the first noticeable sign that something is wrong in herds fed a total mixed ration.
Signs of Clinical Ketosis
When ketosis progresses beyond the subclinical stage, it unfolds in recognizable phases. In the earliest stage, cows begin refusing grain and concentrates while still eating hay or grass. They may chew on sand, pebbles, or bedding (a behavior called pica), move reluctantly, and appear unsteady on their feet. Some rest with their heads pressed into the bedding.
As the disease advances, appetite drops sharply and the cow becomes dull and apathetic. Milk production falls noticeably, and the milk itself changes: fat content can climb as high as 5%, while protein drops. A distinctive sweet, fruity smell of acetone becomes detectable on the cow’s breath and in her urine. Feces turn hard, dry, and coated with mucus. Affected cows often stand with their heads low and eyes closed, appearing to doze.
In the most severe stage, neurological symptoms appear. Cows may walk forward aimlessly, experience seizures, drool heavily, and become extremely sensitive to noise or touch. Some make repetitive chewing or drinking motions, dipping their muzzle into the water trough and mouthing loudly without actually drinking. This nervous form of ketosis, while less common, is unmistakable and requires immediate attention.
How Ketosis Is Detected
Because the subclinical form causes the most total economic damage across a herd, routine testing in early lactation is the most reliable way to catch ketosis before it becomes visible. The gold standard is a blood test measuring a ketone body called beta-hydroxybutyrate (BHB). Handheld meters designed for cowside use give results in seconds from a drop of blood, typically drawn from an ear vein.
Milk and urine test strips offer a less invasive alternative but trade some accuracy. In head-to-head comparisons, urine strips correctly identified about 77% of truly ketotic cows (sensitivity) with 94% accuracy in ruling out healthy cows (specificity). Milk strips were somewhat less sensitive at 61%, though their specificity was similarly high at 91%. In practice, this means milk strips will miss a meaningful number of subclinical cases. Many farms use milk strips as a screening tool and follow up positives or borderline results with a blood test.
Most testing programs target cows between 3 and 14 days in milk, which captures the window when both Type I and Type II ketosis are most likely to be developing.
Treatment Approaches
The immediate goal of treatment is to restore the cow’s energy supply and break the cycle of fat mobilization. For Type I ketosis, the standard approach is oral propylene glycol, a syrupy liquid the liver converts directly into glucose. Typical dosing is 6 to 16 ounces per cow per day for up to 10 days, with severe cases sometimes requiring more. Cows with clinical ketosis often receive intravenous glucose from a veterinarian for a faster initial response, followed by oral propylene glycol to sustain improvement.
Type II ketosis is more challenging. Because the underlying problem involves a fatty, poorly functioning liver and insulin resistance, simply pushing glucose is not always enough. Treatment for these cows focuses on supporting liver recovery and managing the broader metabolic disruption. Response to treatment tends to be slower, and some cows with severe fatty liver do not recover fully.
Prevention Starts Before Calving
The most effective prevention strategies focus on the dry period, well before the cow enters the danger zone of early lactation. Body condition at calving is one of the biggest controllable risk factors. The recommended target is a body condition score of 3.0 on the standard 1-to-5 scale. Cows that calve fatter than this are primed for excessive fat mobilization, increasing their risk of Type II ketosis. Cows that lose more than 1.0 point of body condition after calving are also at elevated risk, regardless of where they started.
Feeding management during the transition period (roughly three weeks before through three weeks after calving) plays an equally important role. The goal is to maximize dry matter intake so the cow enters lactation with a functioning rumen and strong appetite. Overcrowding at the feed bunk, abrupt diet changes, and heat stress all suppress intake and push cows toward a deeper energy deficit. Farms that manage these factors well tend to see lower ketosis rates, fewer displaced abomasums, better fertility, and steadier milk production through the first months of lactation.