Ketosis (acetonemia) is the most common metabolic disorder seen after calving in dairy cattle. It is characterized by increased adipose mobilization as a consequence of negative energy balance (NEB) and by the accumulation of ketone bodies (β-hydroxybutyrate, acetoacetate, and acetone) in the liver and blood. Subclinical ketosis spreads silently through the herd before obvious clinical signs appear and has destructive effects on milk yield, reproductive performance, and immune function. This article reviews ketosis pathophysiology, subclinical ketosis screening protocols, treatment approaches, and herd-level prevention strategies in light of the current literature.
Economic Impact
Subclinical ketosis prevalence commonly ranges from 40-60% in dairy herds. Each subclinical ketosis case causes an economic loss of about $250-375 per cow through lower milk yield, impaired fertility, secondary disease, and premature culling (McArt et al., 2015). In clinical ketosis, this cost can exceed $800.
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Calculate the Ration1. Pathophysiology of Ketosis
Ketosis develops when the increasing glucose demand for milk synthesis after calving cannot be fully met. In the dairy cow, about 85% of glucose is produced in the liver through gluconeogenesis, and glucose demand rises by 2.5-3 times at the beginning of lactation. When dry matter intake (DMI) cannot keep pace with that demand, body fat mobilization is triggered (Herdt, 2000).
Mechanism of Ketosis Development
Milk yield ↑
DMI ↓
Energy deficit
Adipose breakdown
NEFA ↑↑
Blood NEFA >0.7 mEq/L
Liver capacity is exceeded
Partial oxidation ↑
Ketone production ↑↑
BHB ≥1.2 mmol/L
Hepatic lipidosis
Immunosuppression
1.1 Ketone Bodies and Their Metabolism
Partial oxidation of NEFA in the liver produces three ketone bodies. These compounds can be used as energy substrates by peripheral tissues such as muscle, kidney, and mammary gland, but they accumulate in blood when their rate of production exceeds the tissues' capacity for use (Duffield, 2000).
| Ketone Body | Proportion in Blood | Clinical Importance | Measurement Method |
|---|---|---|---|
| β-Hydroxybutyrate (BHB) | 70-80% | Gold-standard diagnostic criterion | Blood (portable meter), milk (test strip) |
| Acetoacetate (AcAc) | 15-20% | Detected in urine by the Rothera test | Urine (Rothera), milk |
| Acetone | 5-10% | Characteristic fruity / acetone odor on breath | Clinical smell assessment, breath analysis |
1.2 Types of Ketosis
- Timing: 3-6 weeks after calving (near peak lactation)
- Cause: Inadequate glucogenic precursor supply
- Profile: Low glucose, low insulin, high BHB
- Liver: Normal or mildly fatty
- Treatment response: Good with glucose + PG
- Timing: First 1-2 weeks after calving
- Cause: Excessive NEFA influx causing hepatic lipidosis
- Profile: Normal/high glucose, high insulin, high NEFA
- Liver: Severe fat infiltration (>10% TG)
- Treatment response: Poor, guarded prognosis
- Timing: Any stage of lactation
- Cause: Poor-quality silage with high butyric acid
- Profile: Dietary butyrate is converted to BHB
- Liver: Usually normal
- Treatment: Correct the silage quality problem
2. Subclinical Ketosis: The Silent Threat
Subclinical ketosis (SCK) is defined as a blood BHB concentration of ≥1.2 mmol/L in the absence of obvious clinical signs such as reduced appetite, milk drop, or acetone odor. SCK is 5-10 times more common than clinical ketosis and causes major economic losses when not detected at the herd level (Duffield et al., 2009).
Hidden Effects of Subclinical Ketosis
| Area Affected | Consequence | Source |
|---|---|---|
| Milk yield | 1.0-2.0 kg/day loss during the first 30 days | Ospina et al., 2010 |
| Displaced abomasum | Risk increases by 6-8 times | LeBlanc et al., 2005 |
| Metritis | Risk increases by 3 times | Duffield et al., 2009 |
| Clinical mastitis | Risk increases by 1.5-2 times | Suthar et al., 2013 |
| Pregnancy at first insemination | 20-30% reduction | Walsh et al., 2007 |
| Early culling | Risk increases 2-3 times during the first 30 days | McArt et al., 2012 |
3. Diagnostic and Screening Methods
3.1 Blood BHB Measurement (Gold Standard)
Portable ketone meters such as Precision Xtra®, BHBCheck®, and FreeStyle Optium Neo® allow BHB measurement from a drop of blood taken from the tail vein or ear vein. Reported sensitivity is 85-95% and specificity is 95-98% (Iwersen et al., 2009).
BHB Cut-Off Values and Interpretation
| BHB Concentration (mmol/L) | Status | Action |
|---|---|---|
| <0.8 | Normal | Continue routine monitoring |
| 0.8-1.1 | At risk (gray zone) | Retest after 48 hours and monitor DMI closely |
| 1.2-2.9 | Subclinical ketosis | Propylene glycol 300-500 mL/day for 3-5 days |
| ≥3.0 | Clinical ketosis | IV dextrose + PG + supportive treatment |
3.2 Other Diagnostic Methods
| Method | Sample | Sensitivity | Specificity | Advantage / Limitation |
|---|---|---|---|---|
| Blood BHB (portable) | Blood | 85-95% | 95-98% | Gold standard, rapid, inexpensive |
| Milk BHB (KetoTest®) | Milk | 70-85% | 80-90% | Convenient during milking, but less accurate |
| Urine ketones (Rothera) | Urine | 50-70% | 90-95% | Cheap but less sensitive; mainly detects AcAc |
| Milk MIR spectroscopy | Milk | 75-85% | 85-90% | Ideal for herd screening and DHI integration |
| Milk fat:protein ratio | Milk | 55-65% | 70-80% | Useful as a screen (>1.5 suggests risk), but low accuracy |
3.3 Herd-Level Screening Protocol
Recommended Screening Protocol (McArt et al., 2012)
- Target group: All cows between 3 and 16 days in milk
- Frequency: 2-3 times per week, ideally every 2 days
- Method: Blood BHB measurement with a portable ketone meter
- Timing: Before the morning feeding, when BHB tends to be highest
- Threshold: Start treatment if BHB is ≥1.2 mmol/L
- Records: Record each cow's BHB value, treatment, and outcome
- Herd target: Keep SCK prevalence below 15% of tested cows
4. Treatment Protocols
4.1 Treatment of Subclinical Ketosis
| Treatment | Dose and Administration | Mechanism of Action | Success Rate |
|---|---|---|---|
| Propylene glycol (PG) | 300-500 mL oral drench once daily for 3-5 days | Converted to propionate in the rumen and then to glucose in the liver | 70-85% (BHB falls below 1.2) |
| PG + dextrose combination | PG 300 mL orally + 500 mL of 50% dextrose IV on day 1 | Rapid glucose support plus sustained gluconeogenesis | 85-95% |
4.2 Treatment of Clinical Ketosis
Clinical Ketosis Treatment Protocol
| Step | Application | Note |
|---|---|---|
| 1. IV dextrose | 500 mL of 50% dextrose IV, slow infusion over 5-10 min | Rapid glucose rise, but the effect lasts only 2-4 hours |
| 2. Propylene glycol | 500 mL oral drench twice daily for 5 days | Provides sustained support for gluconeogenesis |
| 3. Dexamethasone | 10-20 mg IM, single dose (controversial) | Stimulates gluconeogenesis but carries immunosuppressive risk |
| 4. Vitamin B12 | 5-10 mg IM | Acts as a gluconeogenic cofactor, especially if cobalt is low |
| 5. Supportive care | High-quality forage, free access to water, comfortable environment | Aims to improve DMI and overall recovery |
Monitoring the Treatment Response
BHB should be rechecked 48-72 hours after treatment begins. If BHB remains ≥1.2 mmol/L, treatment should continue. If BHB does not decline after 5 days of therapy, investigate an underlying cause such as type II ketosis (fatty liver) or displaced abomasum. In type II ketosis, the prognosis is poor and culling may become necessary.
5. Risk Factors
- Calving BCS ≥3.75: Ketosis risk increases by 3-4 times
- High milk yield: More than 40 kg/day deepens NEB
- Multiparous cows: 2-3 times higher risk than primiparous cows
- Ketosis in the previous lactation: Repeat risk is 40-50%
- Twin pregnancy: Larger fetal burden and lower DMI
- Dystocia: Stress contributes to a decline in DMI
- Excess energy during the dry period: Overconditioned cows at calving predispose to type II ketosis
- Insufficient bunk space: Dominant cows eat first while others are restricted
- Stress from regrouping: Frequent group changes before or after calving
- Poor-quality silage: High butyric acid predisposes to butyric ketosis
- Heat stress: Can reduce DMI by 10-30%
- Insufficient water access: Limits DMI and recovery
6. Prevention Strategies
6.1 Nutritional Strategies
| Strategy | Application | Effect | Strength of Evidence |
|---|---|---|---|
| Controlled energy during the dry period | NEL 1.25-1.35 Mcal/kg DM, energy ≤100% of requirement | Postpartum NEFA and BHB ↓, DMI ↑ | Strong |
| Protected choline | 12-15 g/day RPC from −21 to +21 days | Hepatic lipidosis ↓, VLDL export ↑ | Strong |
| Propylene glycol (prophylactic) | 300 mL/day orally from 10 days before to 10 days after calving | SCK incidence ↓ by 40-50% | Strong |
| Protected methionine | Methionine at 2.2-2.5% of MP | Glutathione synthesis ↑, oxidative stress ↓ | Moderate to strong |
| Monensin (CRC bolus) | Controlled-release capsule, 3 weeks before calving | Rumen propionate ↑, SCK incidence ↓ by 25-30% | Strong |
| Niacin (vitamin B3) | 6-12 g/day, preferably in protected form | Possible inhibition of lipolysis (evidence mixed) | Weak to moderate |
6.2 Management Strategies
Ketosis Prevention Management Protocol
- BCS management: BCS of 3.0-3.25 at dry-off and again at calving
- Bunk space: At least 76 cm of bunk space per cow in the fresh group
- Grouping: Separate prepartum and postpartum groups with minimal regrouping
- Comfort: Adequate bedding, ventilation, and unrestricted access to water
- TMR management: Push up feed at least twice daily, provide fresh TMR, and control particle size
- Stress minimization: Quiet calving area and avoidance of overcrowding
- Routine screening: BHB testing from 3 to 16 DIM
7. Relationship Between Ketosis and Other Diseases
Ketosis is not an isolated disorder. It sits at the center of the transition-cow disease cascade. Subclinical ketosis sharply increases the risk of many secondary disorders (Suthar et al., 2013).
Ketosis → Secondary Disease Cascade
| Secondary Disease | Increase in Risk | Mechanism |
|---|---|---|
| Displaced abomasum (DA) | 6-8 times | Hypomotility, abomasal atony, gas accumulation |
| Metritis | 3 times | Immunosuppression and neutrophil dysfunction |
| Clinical mastitis | 1.5-2 times | BHB reduces leukocyte chemotaxis and phagocytosis |
| Retained placenta | 2-3 times | Immunosuppression and reduced uterine contractility |
| Lameness (laminitis) | 2 times | Linked with subclinical acidosis and vascular damage |
8. NEFA and BHB: Predictive Value
The large study by Ospina et al. (2010) showed that prepartum NEFA and postpartum BHB values have strong predictive value for metabolic disease risk.
| Biomarker | Period | Threshold | Predicted Risk |
|---|---|---|---|
| NEFA | Prepartum (−14 to −3 days) | ≥0.3 mEq/L | DA risk ×3.6, ketosis risk ×2.0, metritis risk ×1.8 |
| NEFA | Postpartum (3-14 days) | ≥0.7 mEq/L | DA risk ×4.0, culling risk ×2.0 |
| BHB | Postpartum (3-16 days) | ≥1.2 mmol/L | DA risk ×6.3, metritis risk ×3.3 |
| BHB | Postpartum (first test) | ≥1.4 mmol/L | Clinical ketosis risk ×5.0 |
9. Herd-Level Monitoring and Success Criteria
| Parameter | Target | Alarm Threshold | Measurement |
|---|---|---|---|
| SCK prevalence (BHB ≥1.2) | <15% | >25% | Weekly BHB screening |
| Clinical ketosis incidence | <5% | >8% | Clinical records |
| Milk fat:protein ratio >1.5 | <15% (first test) | >25% | DHI / milk analysis |
| DA incidence | <3% | >5% | Clinical records |
| Postpartum BCS loss | ≤0.75 points within 60 days | >1.0 point | BCS evaluation |
| Time to peak milk yield | Weeks 6-8 | >10 weeks | Milk records |
10. References
- Duffield, T. F. (2000). Subclinical ketosis in lactating dairy cattle. Veterinary Clinics of North America: Food Animal Practice, 16(2), 231-253.
- Duffield, T. F., et al. (2009). Impact of hyperketonemia in early lactation dairy cows on health and production. Journal of Dairy Science, 92(2), 571-580.
- Herdt, T. H. (2000). Ruminant adaptation to negative energy balance: Influences on the etiology of ketosis and fatty liver. Veterinary Clinics of North America: Food Animal Practice, 16(2), 215-230.
- Iwersen, M., et al. (2009). Evaluation of an electronic cowside test to detect subclinical ketosis in dairy cows. Journal of Dairy Science, 92(6), 2618-2624.
- LeBlanc, S. J., et al. (2005). Major advances in disease prevention in dairy cattle. Journal of Dairy Science, 88(4), 1267-1279.
- McArt, J. A. A., et al. (2012). Epidemiology of subclinical ketosis in early lactation dairy cattle. Journal of Dairy Science, 95(9), 5056-5066.
- McArt, J. A. A., et al. (2015). Hyperketonemia in early lactation dairy cattle: A deterministic estimate of component and total cost per case. Journal of Dairy Science, 98(3), 2043-2054.
- Ospina, P. A., et al. (2010). Evaluation of nonesterified fatty acids and β-hydroxybutyrate in transition dairy cattle in the northeastern United States: Critical thresholds for prediction of clinical diseases. Journal of Dairy Science, 93(2), 546-554.
- Suthar, V. S., et al. (2013). Prevalence of subclinical ketosis and relationships with postpartum diseases in European dairy cows. Journal of Dairy Science, 96(5), 2925-2938.
- Walsh, R. B., et al. (2007). The effect of subclinical ketosis in early lactation on reproductive performance of postpartum dairy cows. Journal of Dairy Science, 90(6), 2788-2796.