In the quiet corners of industrial agriculture, a hidden practice links the suffering of horses to the production of pork on dinner tables worldwide. Pregnant mares are subjected to repeated, large-volume blood extractions to harvest a hormone that boosts fertility in pigs — a process that has drawn condemnation from animal welfare organizations for years. This hormone, known as PMSG (Pregnant Mare Serum Gonadotropin) or eCG (equine chorionic gonadotropin), is extracted from the blood of pregnant mares and used to synchronize and increase litter sizes in sows, making pork production more predictable, and profitable.
The scale of this practice is significant. According to documented investigations, more than 10,000 pregnant mares in Argentina and Uruguay, and approximately 5,000 in Iceland, are exploited annually for their blood. On so-called “blood farms,” these animals are often restrained in narrow pens, stressed, and sometimes physically abused during the procedure. Veterinary care is frequently absent, and many mares suffer from severe weight loss, exhaustion, or death due to the repeated loss of up to ten liters of blood per week over several months.
The extracted PMSG is then administered to pigs to induce estrus, increase ovulation rates, and shorten breeding cycles. This allows farmers to synchronize farrowing — the timing of piglet births — across entire herds, streamlining labor, reducing costs, and improving efficiency in large-scale swine operations. While the hormone is also used in sheep and cattle, its primary application remains in industrial pig farming, where economic pressures drive the demand for higher output and faster turnover.
Animal welfare groups have long argued that this practice constitutes systemic animal cruelty. The Animal Welfare Foundation, in collaboration with partner organizations, has documented conditions on blood farms that include physical restraint, blunt force trauma, and prolonged suffering without anesthesia or pain relief. The foals born to these mares are often considered byproducts — many are raised for slaughter shortly after birth, adding another layer to the ethical concerns surrounding the industry.
Despite growing awareness, regulatory oversight remains minimal in many countries where blood farming occurs. There are no international bans on the production or use of PMSG, and few national laws specifically address the welfare of mares used for hormone extraction. In the European Union, while animal transport and slaughter are regulated under Directive 2007/43/EC and Regulation (EC) No 1099/2009, there are no specific rules governing the collection of blood from pregnant equines for hormonal use. This regulatory gap allows the practice to continue largely unchallenged in regions with lax enforcement.
The health implications for the mares are severe. Repeated phlebotomy of this magnitude can lead to hypovolemic shock, anemia, electrolyte imbalances, and compromised immune function. Mares are typically bled from early to mid-pregnancy — a critical window when the placenta produces high levels of PMSG to support fetal development. Disrupting this process not only endangers the mare but may also impair fetal growth, increasing the risk of abortion or stillbirth. Veterinary experts note that recovery between bleeding sessions is often insufficient, especially when performed weekly over extended periods.
From a public health perspective, while PMSG is a protein hormone and not known to persist in meat or pose direct risks to consumers, its use raises broader questions about the ethics of industrial animal production. The reliance on such interventions highlights how economic efficiency is often prioritized over animal welfare in global food systems. Critics argue that sustainable alternatives — such as improved breeding programs, better nutrition, and stress-reducing husbandry practices — could achieve similar productivity gains without compromising animal well-being.
Efforts to end blood farming have gained traction through public awareness campaigns and corporate pressure. Some retailers and food brands have begun auditing their supply chains for links to hormone-induced pig production, though traceability remains tricky due to the complexity of global feed and pharmaceutical networks. Advocacy groups continue to call for clearer labeling, third-party certifications, and incentives for farmers who adopt hormone-free breeding methods.
As of now, there are no scheduled legislative hearings or official investigations announced by major regulatory bodies such as the European Food Safety Authority (EFSA) or the World Organisation for Animal Health (WOAH) specifically targeting PMSG production. Yet, ongoing documentation by NGOs like the Animal Welfare Foundation and the Dr. Med. Henrich Foundation keeps the issue in public discourse, emphasizing the need for transparency and accountability in agricultural practices.
The story of the blood mares is not just about animal suffering — it reflects deeper tensions in how society values life, labor, and profit in the food chain. Until meaningful change occurs, thousands of horses will continue to endure invasive procedures so that piglets can be born on schedule and pork can reach markets at lower cost.
For readers seeking to learn more about animal welfare in agriculture or to support efforts to end exploitative practices, verified information is available through organizations such as the Animal Welfare Foundation (animal-welfare-foundation.org) and the Dr. Med. Henrich Foundation (dr-med-henrich.foundation). These groups provide regularly updated reports, investigation findings, and guidance on how to engage with policymakers and industry stakeholders.
Stay informed. Share this story. And consider how the food on your plate is connected to lives far beyond the farm.