Although horses are not among the most commonly used animals in laboratories, they are still used in biomedical research and pharmaceutical production. Horses may be used to produce certain medical products or in experiments studying human diseases and injuries. Their large size and some physiological similarities to humans have resulted in horses being used in studies involving infectious disease, respiratory illness, and musculoskeletal injuries.
The use of horses in research and pharmaceutical production raises ethical concerns about animal welfare, including issues related to confinement, invasive procedures, and long-term use in experiments. These concerns highlight the importance of developing and adopting modern, human-relevant research methods that do not rely on animals.
Antibody and Antivenom Production
Horses have long been used to produce antibodies for human medicine. In the late 1800s, scientists developed the first diphtheria antitoxin by injecting horses with bacterial toxins and collecting antibodies from their blood. Horses are still used today to produce some antivenoms for snake bites and other venomous animal encounters. Their large size allows significant amounts of antibody-rich plasma to be collected, and their immune systems can generate strong antibody responses.
Because these treatments are derived from animal serum, they can sometimes cause immune reactions in people, including a condition known as serum sickness. The process also requires horses to be repeatedly injected with toxins or venoms and subjected to blood collection procedures, raising ongoing animal welfare concerns.
Hormone Production
Horses are also used in the pharmaceutical industry to produce certain hormone replacement therapies for post-menopausal women. Some medications contain conjugated equine estrogens derived from the urine of pregnant mares, including the drug Premarin (named for “pregnant mares’ urine”).
To collect this urine, mares are repeatedly impregnated and their estrogen-rich urine is gathered during pregnancy. In pregnant mare urine (PMU) operations, mares may spend months in stalls fitted with urine-collection devices. Animal protection groups have raised concerns about restricted movement, potential injuries caused by collection equipment, and the fate of foals and mares who are no longer used for production.
Use in Biomedical and Behavioral Experiments
Horses are also used in experiments intended to study human diseases and test medical treatments. Experiments on horses have included studies of viral infections and respiratory disease. Horses have been studied in connection with hepatitis infections following the discovery of equine hepacivirus. They have also been used in respiratory disease research, including studies of equine asthma and other inflammatory airway conditions.
In addition, behavioral studies have examined stress responses and depression-like states in horses. Some researchers have suggested that chronically stressed domestic horses, particularly those kept in restrictive environments or subjected to demanding workloads, may display behaviors such as apathy that resemble aspects of human depressive states. These findings have prompted concerns about the psychological effects of confinement, intensive use, and other human-imposed conditions on horses.
Musculoskeletal and Regenerative Research
Horses are used in experiments involving cartilage injuries, osteoarthritis, and tendon damage, including studies testing regenerative approaches such as stem cell therapies. Some studies examine naturally occurring conditions in horses, while others involve experimentally inducing injuries or testing treatments on damaged joints.
Research involving horses requires large facilities, specialized equipment, and extensive handling. Their size and weight can place significant stress on injured joints during experiments, raising additional animal welfare concerns.
Moving Toward Human-Relevant Research
Advances in biomedical science are making it increasingly possible to study human diseases without relying on animals. Modern research approaches can provide insights that are directly relevant to human biology while avoiding the ethical concerns associated with animal experimentation.
Please consider making a donation to NAVS’ Animal Sanctuary Assistance Program which supports sanctuaries and rescue organizations providing lifelong care for animals rescued from research laboratories, PMU farms, and other harmful industries.
