Ketosis in Dairy Cattle

Ketosis is a metabolic disorder that arises when the balance between carbohydrate and fat metabolism is disrupted, leading to excessive production of ketone bodies. It primarily affects highproducing dairy cows during the early lactation period, when energy demands outpace dietary intake.

1. Physiology of CarbohydrateFat Metabolism

During the transition from the dry period to lactation, cows experience a sudden increase in glucose requirement for milk synthesis. The liver maintains blood glucose through three main pathways:

• Gluconeogenesis synthesis of glucose from noncarbohydrate precursors (propionate, lactate, glycerol).
• Glycogenolysis breakdown of hepatic glycogen stores.
• Dietary glucose absorption limited in ruminants because most carbohydrates are fermented to volatile fatty acids (VFAs) in the rumen.

If dietary intake cannot meet the demand, the cow mobilizes adipose tissue. Triglycerides are hydrolyzed to nonesterified fatty acids (NEFAs) that travel to the liver. In the liver, NEFAs can be:

• Oxidized for energy.
• Reesterified into triglycerides (risking fatty liver).
• Converted to ketone bodies (acetone, hydroxybutyrate, acetoacetate).

When NEFA influx overwhelms hepatic oxidative capacity, ketogenesis accelerates, and ketone bodies accumulate in blood the hallmark of ketosis.

2. Types of Ketosis

3. Predisposing Factors

• High milk yield potential rapid glucose demand.
• Negative energy balance (NEB) inadequate drymatter intake (DMI) after calving.
• Excessive body condition score (BCS) (>3.5/5) larger fat reserves lead to greater NEFA release.
• Short or abrupt diet changes that impair rumen fermentation.
• Concurrent diseases (e.g., metritis, retained placenta) that further reduce intake.

4. Clinical Signs & Diagnosis

4.1 Clinical Signs

Early signs are often subtle. Look for:

• Lethargy or reduced responsiveness.
• Decreased feed intake, especially of concentrates.
• Reduced milk volume (1030% drop).
• Sweet or acetonelike odor on breath.
• Weight loss despite adequate intake.

4.2 Laboratory Diagnosis

The most reliable indicator is blood hydroxybutyrate (BHB). Common thresholds:

• <1.2mmol/L normal.
• 1.23.0mmol/L subclinical ketosis.
• >3.0mmol/L clinical ketosis.

Other useful tests:

• Milk ketone test strips (quick screening).
• Serum NEFA concentrations (>0.7mmol/L suggest NEB).
• Liver function enzymes (AST, GGT) if fatty liver is suspected.

5. Treatment Strategies

5.1 Immediate Management

• Glucose precursors: Oral dextrose drench (500g/cow) or propylene glycol drench (300mL) administered 23times daily for 23days.
• Intravenous therapy: 500mL of 5% glucose solution or sodium bicarbonate for severely depressed cows.
• Ensure fresh, palatable water and easyaccess feeding stalls.

5.2 Nutritional Adjustments

• Increase dietary energy density add protected fats, ground corn, or rumenbypass starch.
• Provide a glucogenic feed additive such as propylene glycol or monensin.
• Maintain a balanced ration with adequate fiber to preserve rumen function.
• Gradually transition drycow diets to lactation diets to avoid abrupt changes.

5.3 Preventive Measures

• Target BCS of 3.03.25 at calving.
• Monitor DMI closely during the first two weeks postpartum; aim for 1.5% of body weight (dry matter).
• Implement a transition program: 3week diet that gradually increases fermentable carbohydrates and reduces fiber.
• Routine BHB screening at 3, 7, and 14days after calving.
• Address concurrent health issues promptly (e.g., metritis, retained placenta).

6. Economic Impact

Ketosis directly reduces milk production (average 710% loss) and increases the risk of secondary disorders such as displaced abomasum, mastitis, and reproductive failure. The cost per affected cow can range from $150 to $300, factoring treatment, reduced milk revenue, and extended calving intervals.

7. Summary

Ketosis is a common, yet manageable, metabolic disorder in highproducing dairy cattle. Understanding the relationship between carbohydrate shortage and excessive fat mobilisation allows producers to detect early signs, apply rapid treatment, and, most importantly, implement preventive nutrition and management programs. Regular monitoring of BHB and NEFA, combined with a wellstructured transition diet, are the cornerstones of an effective control strategy.

For further reading, see the National Research Council guidelines and the USDA Dairy Production Handbook.