Ketosis (acetonemia) is one of the most common and economically significant metabolic disorders in dairy cattle.
Overview and Clinical Importance
Ketosis (acetonemia) is one of the most common and economically significant metabolic disorders in dairy cattle. It is characterized by elevated blood concentrations of ketone bodies (beta-hydroxybutyrate, acetoacetate, and acetone) resulting from negative energy balance (NEB) during early lactation or late gestation. The condition represents a failure to adapt to the high glucose demands of milk production combined with inadequate dry matter intake.
The disease has substantial economic impact, with studies reporting average herd-level costs of $3,613-$7,371 per year. For every cow showing clinical signs, multiple subclinical cases exist, making this truly the "tip of the iceberg" problem in modern dairy production.
| Step |
Metabolic Event |
| 1 |
Insufficient propionate production leads to hypoglycemia |
| 2 |
Low insulin and high glucagon trigger lipolysis from adipose tissue |
| 3 |
Non-esterified fatty acids (NEFAs) are released into circulation |
| 4 |
Hepatocytes take up NEFAs for beta-oxidation to Acetyl-CoA |
| 5 |
Oxaloacetate depletion (diverted to gluconeogenesis) prevents TCA cycle entry |
| 6 |
Excess Acetyl-CoA is shunted to ketogenesis forming ketone bodies |
Etiology and Pathophysiology
The Energy Crisis in Early Lactation
The fundamental problem in ketosis is the mismatch between glucose demand and glucose supply. Ruminants are unique in that they derive minimal glucose from direct intestinal absorption. Instead, approximately 70% of their glucose must be synthesized via hepatic gluconeogenesis, primarily from propionate (a volatile fatty acid produced during rumen fermentation).
A cow producing 40 liters of milk daily requires approximately 2.25 kg of lactose synthesis, equivalent to about 4.5 kg of glucose (or 18 bottles of 50% dextrose). Meanwhile, the total blood glucose pool is less than 40 g, and cows utilize 50-70 g glucose per hour for maintenance alone. This massive demand, combined with physiologically decreased dry matter intake around parturition, creates the perfect storm for ketosis development.
Ketogenesis Pathway
When energy intake is insufficient, the following cascade occurs:
High-YieldThe key to understanding ketosis is the oxaloacetate bottleneck. When gluconeogenesis depletes oxaloacetate, the TCA cycle cannot process Acetyl-CoA efficiently, forcing its conversion to ketone bodies. This is why propionate (which generates oxaloacetate) is the cornerstone of treatment.
Type I vs Type II Ketosis
NAVLE TipWhen a ketosis case occurs within the first week postpartum (Type II), always investigate for fatty liver and concurrent diseases. These cases are often refractory to standard treatment and require more aggressive intervention. In contrast, Type I ketosis occurring around peak lactation typically responds well to propylene glycol therapy.
| Feature |
Type I (Primary) |
Type II (Secondary) |
| Timing |
3-6 weeks postpartum (peak lactation) |
First 1-2 weeks postpartum |
| Primary Cause |
Insufficient gluconeogenic precursors |
Fatty liver and excessive fat mobilization |
| Blood Glucose |
Low (hypoglycemia) |
Normal to transiently high |
| Insulin |
Low |
High (insulin resistance) |
| Liver Status |
Usually normal |
Fatty infiltration common |
| Risk Factors |
High producers, inadequate energy density |
Overconditioned cows (BCS greater than 4.0) |
| Treatment Response |
Generally good |
Often refractory |
Clinical Presentation
Wasting Form (Most Common)
The wasting form accounts for approximately 90% of clinical cases and develops gradually over 2-4 days:
Nervous Form (Less Common)
The nervous form occurs in approximately 10% of clinical cases and presents with episodic neurological signs lasting 1-2 hours, recurring at 8-12 hour intervals:
- Pica - licking walls, gates, metal bars, eating sand/pebbles
- Abnormal chewing movements and excessive salivation
- Circling and crossing legs (early sign of hypoglycemia)
- Apparent blindness with incoordination
- Bellowing and aggression
- Hyperesthesia - exaggerated response to stimuli
High-YieldThe nervous form of ketosis can mimic rabies! Key differentiators include: episodic nature (rabies is progressive), absence of fever, response to IV dextrose, and elevated ketones. Always include rabies in the differential for any cow showing neurological signs.
Subclinical Ketosis (SCK)
Critical concept: 80-90% of ketosis cases are subclinical with no visible signs. Studies report prevalence of 20-50% in the first two weeks postpartum. SCK is defined as elevated blood BHB (greater than or equal to 1.2 mmol/L) without clinical signs.
Consequences of SCK include:
- 4.4-6% reduction in milk production over entire lactation
- 3.4-fold increased risk of metritis
- 3.1-fold increased risk of displaced abomasum
- Reduced first-service conception rates
- Increased risk of early culling
| Clinical Sign |
Clinical Details |
| Selective Anorexia |
Refuses concentrates but continues eating hay/roughage (classic presentation) |
| Milk Production |
Drop of 3-5 liters/day over 5-6 days before obvious clinical signs |
| Body Condition |
Rapid loss of subcutaneous fat, "woody appearance" |
| Feces |
Firm, dry, "waxy" consistency, often covered with mucus |
| Breath/Milk Odor |
Sweet acetone/"pear drop" smell (not always detectable) |
| Coat |
Dull, rough, "stary" appearance |
| Vital Parameters |
Temperature, pulse, and respiratory rate usually normal |
Diagnosis
Diagnostic Thresholds
Cowside Diagnostic Tests
High-YieldBlood BHB testing using handheld meters (Precision Xtra or BHBCheck) is the gold standard for cowside diagnosis with 95-100% sensitivity and specificity. For herd-level monitoring, test 12 or more fresh cows (3-16 DIM). If greater than 10% test positive, the herd has a ketosis problem requiring intervention.
Differential Diagnosis
Wasting Form:
- Displaced abomasum (LDA/RDA) - often concurrent with ketosis
- Traumatic reticuloperitonitis (hardware disease)
- Primary indigestion
- Cystitis and pyelonephritis
Nervous Form:
- Rabies - always on differential for any neurological case
- Hypomagnesemia (grass tetany)
- Bovine spongiform encephalopathy
- Lead poisoning
| Test/Sample |
SCK Threshold |
Clinical Ketosis |
| Blood BHB |
greater than or equal to 1.2 mmol/L (12.5 mg/dL) |
greater than or equal to 3.0 mmol/L (31.2 mg/dL) |
| Blood Glucose |
Normal: 50-65 mg/dL |
20-40 mg/dL (hypoglycemia) |
| Milk BHB |
greater than or equal to 100 micromol/L |
Variable |
| Urine Acetoacetate |
greater than or equal to 5 mg/dL |
Strongly positive |
| Milk Fat:Protein Ratio |
greater than 1.4-1.5 |
greater than 1.7 |
Treatment
Treatment goals: 1) Restore normoglycemia, 2) Decrease ketone body production, 3) Identify and treat underlying causes
Treatment Protocols by Severity
Drug Mechanisms and Considerations
NAVLE TipPropylene glycol is the most efficacious and evidence-based treatment for ketosis. IV dextrose provides only temporary benefit (2-4 hours) because the renal threshold for glucose is only 150 mg/dL - most of the administered glucose is rapidly excreted. Glucocorticoids are controversial and should be avoided in cows with concurrent infectious disease due to immunosuppression.
| Test |
Sample |
Sensitivity |
Best Use |
| Precision Xtra/BHBCheck |
Whole blood |
95-100% |
Gold standard cowside |
| Ketostix |
Urine |
78% |
Herd screening |
| KetoTest |
Milk |
73-80% |
Herd screening |
| KetoCheck Powder |
Milk |
41% |
Confirming clinical cases |
Prevention and Management
Body Condition Score Targets
Critical principle: Maintain optimal BCS of 3.0-3.5 at calving. Cows with BCS greater than or equal to 4.0 have significantly increased risk of ketosis due to decreased DMI prepartum and excessive fat mobilization.
Transition Cow Management
- Far-off dry period (60-21 days prepartum): Feed high-fiber, moderate-energy diet to maintain BCS
- Close-up period (21-0 days prepartum): Gradually increase energy density; introduce milking ration components
- Fresh cow period (0-21 DIM): Maximize DMI; monitor for ketosis; separate housing to reduce competition
- Stocking density: One free stall per cow; 120-150 sq ft per cow on bedded packs; adequate bunk space
Preventive Feed Additives
High-YieldMonensin is the most well-documented feed additive for ketosis prevention. It works by selecting for Gram-negative rumen bacteria that produce propionate while inhibiting Gram-positive bacteria that produce acetate and butyrate. In Europe, the controlled-release bolus (Kexxtone) is the only approved form for dairy cattle.
| Severity |
Treatment Protocol |
Notes |
| Mild to Moderate SCK |
Propylene glycol 250-400 g (8-14 oz) PO q24h for 3-5 days |
Producer-administered; most cost-effective |
| Clinical Ketosis |
Propylene glycol PO + 500 mL 50% dextrose IV + Dexamethasone 5-20 mg IM + B vitamins |
Veterinarian-initiated; multimodal approach |
| Nervous Ketosis |
500 mL 50% dextrose IV (immediate) + propylene glycol PO + continue dextrose q12h as needed |
IV glucose essential for rapid response |
| Refractory Type II |
Repeated 5-day PG course + Vitamin B12 1.25-5 mg IM q24h + consider reduced milking frequency |
Often associated with fatty liver; prolonged treatment needed |
Memory Aids
"KETOSIS" Mnemonic for Clinical Signs
- K - Ketone odor (sweet acetone/pear drops)
- E - Eating selectively (refuses concentrates, eats hay)
- T - Thin cow syndrome (rapid weight loss)
- O - Output decreased (milk production drops)
- S - Stool changes (firm, dry, waxy feces)
- I - Iceberg phenomenon (for every clinical case, many subclinical)
- S - Signs may be nervous (pica, licking, circling)
"BHB 1-2-3" Rule for Diagnosis
- 1.2 mmol/L = Subclinical ketosis threshold
- 2 weeks = Peak risk period postpartum
- 3.0 mmol/L = Clinical ketosis threshold
"PG for KG" (Propylene Glycol for Ketogenic state)
250-400 grams PO daily for 3-5 days = Standard treatment protocol
| Drug |
Mechanism |
Cautions |
| Propylene Glycol |
Gluconeogenic precursor; converted to propionate and glucose in liver; increases serum glucose and insulin; decreases BHB and NEFA |
Requires functional liver; CNS depression if overdosed |
| 50% Dextrose |
Direct glucose supplementation; suppresses NEFA release and hepatic ketogenesis temporarily |
Effect lasts only 2-4 hours; must give IV; relapses common |
| Glucocorticoids |
Stimulates gluconeogenesis from amino acids; decreases tissue glucose uptake; reduces milk production |
Avoid with concurrent infection; immunosuppressive dose is 0.04-0.05 mg/kg |
| Vitamin B12 |
Cofactor for propionate metabolism; enhances gluconeogenesis; particularly useful in hypoglycemic cases |
Most beneficial with concurrent PG therapy |
| BCS at Calving |
Risk Category |
Action |
| less than 3.0 |
Low risk but suboptimal |
Feed to gain condition in late lactation |
| 3.0-3.5 |
OPTIMAL |
Maintain through dry period |
| 3.75-4.0 |
Elevated risk |
Reduce energy in late lactation; monitor closely |
| greater than 4.0 |
HIGH RISK |
Consider prophylactic PG; very close monitoring |
| Additive |
Mechanism/Dose |
Evidence Level |
| Monensin (Rumensin) |
Ionophore; increases propionate:acetate ratio; reduces ketosis incidence by greater than 50%. Available as feed additive or controlled-release bolus (Kexxtone in EU) |
Strong |
| Propylene Glycol |
Gluconeogenic precursor; 300 mL daily postpartum for high-risk cows |
Strong |
| Rumen-Protected Choline |
Reduces hepatic fat accumulation; improves VLDL export from liver |
Moderate |
| Niacin |
Inhibits lipolysis; reduces NEFA release. Must be rumen-protected form |
Moderate |
| Calcium Propionate |
Gluconeogenic precursor + calcium supplementation; 500 g at calving |
Moderate |