Metabolic hypophospathemia (postparturient hemoglobinuria PPH)
- Definition
Periparturient hemoglobinuria (PPH), also called post‑parturient hemoglobinuria, is a metabolic and hematologic disorder primarily affecting high‑producing dairy cows during late pregnancy or early lactation. It is characterized by intravascular hemolysis, hemoglobinuria, anemia, and, in severe cases, death. The disease is closely associated with severe hypophosphatemia, oxidative stress, and increased metabolic demands during lactation.
PPH is reported globally but is most common in high‑yielding dairy breeds such as Holstein‑Friesians. Cows between 4–8 years and those in the first 4–6 weeks of lactation are most frequently affected. Incidence increases in areas with dietary phosphorus deficiency or in herds fed high‑oxalate roughages.
Etiology
1-Hypophosphatemia: The central etiological factor. Low phosphorus leads to:
- reduced ATP synthesis
- fragile erythrocyte membranes
- decreased 2,3‑DPG levels
- impaired glycolysis: This instability increases susceptibility to oxidative hemolysis.
2-Oxidative Stress: High milk production increases oxidative load. Reduced glutathione levels weaken erythrocytes, leading to hemolysis.
3-Dietary Risk Factors
- Diets deficient in phosphorus (like Barseem rich in Ca deficiency in P)
- High-oxalate feeds (beet tops)
- Imbalanced Ca:P ratio (2:1).
- The disease mostly occurs in spring season in egypt due to feeding mainly on Barseem
4-Increased Metabolic Demand
During early lactation, phosphorus is heavily diverted toward milk production, exacerbating pre-existing dietary deficiency.
Pathogenesis
PPH develops through a sequence of metabolic events:
1. Negative phosphorus balance occurs due to increased lactational demand.
2. Serum inorganic phosphorus falls below 1.0 mmol/L, impairing erythrocyte energy metabolism.
3. ATP depletion leads to membrane fragility.
4. Oxidative stress causes massive intravascular hemolysis.
5. Free hemoglobin saturates plasma-binding proteins and spills into urine → hemoglobinuria.
6. Resulting anemia, hypoxia, and renal hemoglobin damage contribute to morbidity.