Omeprazole Reduces Calcium Digestibility in Thoroughbred Horses.
Authors: Pagan Joe D, Petroski-Rose Laura, Mann Alana, Hauss Ashlee
Journal: Journal of equine veterinary science
Summary
Omeprazole therapy, commonly prescribed to prevent and treat equine gastric ulcer syndrome, significantly impairs calcium absorption in Thoroughbreds regardless of whether limestone or marine-derived calcium sources are used in the diet. In a controlled crossover trial spanning four 21-day periods with 6-day collection phases, researchers measured faecal calcium excretion and blood parameters in horses receiving either 60 g daily marine-derived calcium or 50 g daily limestone (both providing approximately 45 g total dietary calcium), with omeprazole administered at 3.91 mg/kg bodyweight daily for the final 14 days of each period. The proton pump inhibitor reduced apparent calcium digestibility by 20.3% with limestone (from 52.0% to 41.4%) and 15.6% with marine-derived sources (from 55.1% to 46.5%), whilst having no significant effect on the digestibility of phosphorus, magnesium, potassium, sodium, or trace minerals; serum gastrin concentrations doubled in treated horses, reflecting the expected physiological response to acid suppression. For equine practitioners managing horses on long-term omeprazole therapy—particularly performance animals requiring optimal mineral status for bone development and maintenance—these findings suggest the need for increased dietary calcium provision or supplementation to offset the substantial reduction in bioavailability, and warrant consideration during nutritional planning for young stock, breeding stock, and horses with marginal calcium intake.
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Practical Takeaways
- •Horses receiving omeprazole for gastric ulcer treatment may require increased dietary calcium intake or supplementation, particularly if using limestone as the calcium source
- •Marine-derived calcium sources are more bioavailable than limestone regardless of omeprazole use, making them preferable for horses on acid-suppressing medications
- •Monitor calcium status (via blood work and clinical signs) in horses on long-term omeprazole therapy, as reduced digestibility could contribute to deficiency over time
Key Findings
- •Omeprazole reduced apparent calcium digestibility from 52.0% to 41.4% in limestone-fed horses (20.3% decrease) and from 55.1% to 46.5% in BMC-fed horses (15.6% decrease)
- •Marine-derived calcium (BMC) resulted in higher overall calcium digestibility (50.8%) compared to limestone (46.7%)
- •Serum gastrin doubled in omeprazole-treated horses compared to untreated controls
- •Omeprazole had no significant effect on digestibility of phosphorus, magnesium, potassium, sodium, iron, copper, zinc, or manganese