Blood Doping in Horses: An Insidious Threat to Fair Play

Written by: Camryn McNeill, B.B.R.M.
Reviewed by: Dr. Madison Ricard, DVM, PhD, DACVP, PAS
Veterinary Review: Dr. Jennifer Skaggs, DVM

Blood doping in horses is a performance-enhancing practice that boosts the blood’s oxygen-carrying capacity by artificially increasing red blood cell (RBC) counts. In equestrian sports, blood doping is used to improve stamina, endurance, and recovery, allowing horses to perform at high intensity for a prolonged period.

Blood doping is an effective performance enhancement that poses serious health risks and ethical concerns. This practice undermines fair competition and violates animal welfare principles by prioritizing competitive advantage over the horse’s well-being. As a result, blood doping is banned in equestrian sports, with strict regulations in place to detect and prevent its use.

Blood Doping Methods

Blood doping enhances athletic performance by increasing the oxygen-carrying capacity of blood, which boosts endurance and reduces fatigue during intense physical activity. While blood doping encompasses a range of methods and substances, the following are the most studied in horses:

Synthetic Erythropoietin (rHuEPO)

Erythropoietin (EPO) is a natural hormone that stimulates RBC production in the bone marrow, increasing the blood’s oxygen-carrying capacity.

This process, known as erythropoiesis, is critical for improving endurance and performance during physical exertion.

In horses, recombinant human EPO (rHuEPO), a synthetic version of EPO, is administered to raise RBC levels. This improves endurance and recovery during races and endurance events.

Due to concerns over horse welfare, the Fédération Équestre Internationale (FEI) placed rHuEPO on the banned substances list in 2010.

Filgrastim (Granulocyte Colony-Stimulating Factor)

Filgrastim (a form of human Granulocyte Colony-Stimulating Factor or G-CSF) stimulates production of certain blood cells. It is often used alongside rHuEPO in stem cell treatments and to treat conditions like anemia.

In horses, filgrastim can be misused to enhance performance by boosting red blood cell production.

Hypoxia-inducible factor Modifiers/Stabilizers

Hypoxia-inducible factor (HIF) helps the body respond to low oxygen levels (hypoxia). It activates genes that promote oxygen delivery and increase red blood cell production, allowing cells to adapt to oxygen deficiency.

HIF-1 is a key protein in this process, as it increases red blood cell production and improves oxygen delivery. HIF-1 modifiers mimic this effect, artificially boosting red blood cell production and oxygen-carrying capacity, which may enhance athletic performance.

Common HIF-1 modifiers/stabilizers include cobalt and roxadustat. These substances are banned in equine sports by regulatory bodies such as WADA and IFHA because they have the potential to enhance performance by increasing oxygen availability.

Cobalt Chloride

Cobalt chloride (CoCl2) is believed to act as an HIF-1 modifier, stimulating erythropoietin (EPO) production. EPO signals the bone marrow to produce more red blood cells and potentially enhances the horse’s oxygen-carrying capacity, though there is currently no scientific evidence that it enhances athletic performance in horses.

Moreover, high doses of cobalt chloride can be harmful. Although its long-term effects on horses are not well understood, cobalt toxicity has been documented in other species after prolonged exposure, even at low doses.

Roxadustat

Roxadustat is a drug that stabilizes hypoxia-inducible factor (HIF), which increases levels of erythropoietin (EPO) and boosts red blood cell production.
Roxadustat is used medically to treat anemia in chronic kidney disease patients. Its use is strictly prohibited in equine sports.

Myo-inositol trispyrophosphate (ITPP)

Myo-inositol trispyrophosphate (ITPP) is a drug that boosts oxygen delivery by improving oxygen release from red blood cells. In horses, it is used to boost stamina, particularly in high-performance disciplines such as racing.

Health Risks & Side Effects

Blood doping in horses carries serious health risks. These practices can harm multiple organ systems and severely compromise the horse’s overall well-being.
Complications of blood doping vary based on the substance used and the duration of administration. Affected horses may show:

• Lethargy or Fatigue
• Decreased Performance
• Poor Recovery
• Arrhythmias
• Increased Blood Pressure
• Decreased Peripheral Circulation
• Labored Breathing (Dyspnea)
• Anemia
• Pale Mucous Membranes
• Inflammation

Cobalt Chloride Toxicity

Cobalt salts used in blood doping for horses pose serious health risks. Cobalt is an essential trace mineral in the equine diet, but when used excessively, it can cause toxicity, leading to serious complications. While research on cobalt’s long-term effects in horses is limited, its toxicity is well documented in humans.

While equine studies are lacking, one study in horses showed that intravenous administration of cobalt chloride can lead to irregular blood pressure, signs of distress, and elevated stress markers. Repeated doses may lead to cobalt accumulation in the body and long-term damage to multiple systems.

Recombinant Human Erythropoietin (rHuEPO)

The use of rHuEPO in horses to increase red blood cell production carries significant risks. Repeated administration of rHuEPO, which differs structurally from the horse’s natural EPO, can trigger an immune response.

This immune reaction may interfere with the horse’s ability to produce its own EPO, potentially leading to life-threatening anemia. The immune system may attack both the synthetic and natural EPO, reducing the blood’s oxygen-carrying capacity and causing severe health issues.

Detection of Blood Doping in Horses

Detecting blood doping in horses is paramount for ensuring fair competition and safeguarding horse welfare.

Advanced techniques aim to identify specific biomarkers or metabolites associated with doping. Available testing methods for blood and plasma analysis include:

• Erythropoietin (EPO) Testing
• Cobalt Testing
• Hemoglobin and Hematocrit Tests
• Immunoassays (ELISAs)
• Mass Spectrometry (LC-MS)

Enforcement Challenges

Enforcing doping regulations in equine sports presents significant challenges. The Fédération Équestre Internationale (FEI) has set strict rules against performance-enhancing drugs and practices, including all known forms of blood doping.

Despite existing regulations, detection remains difficult due to advanced techniques and short detection windows, allowing some violations to evade scrutiny.

Additionally, the absence of a unified global authority for doping control in horse racing leads to inconsistent anti-doping programs across regions. This lack of standardization complicates efforts to ensure fair competition, protect equine welfare, and maintain the integrity of the sport.