A new study led by Australian veterinarians has highlighted the challenge of identifying pain in horses with gastric ulcers and emphasized the need for more reliable detection methods. Gastric ulcers are a common issue in horses, especially in the racing industry, but scientists still struggle to determine which animals are in pain or how serious the ulcers are. Researchers from Adelaide University tested a potential new blood-based method to detect biological changes linked to gastric ulcers. The study, published in The Veterinary Journal, examined whether immune cells in a horse's blood could provide a measurable signal of a condition called Equine Gastric Ulcer Syndrome (EGUS). Blood samples were taken from 77 horses, and immune cells were exposed to substances meant to trigger an immune response. The researchers measured the production of a molecule called interleukin-1 beta (IL-1β), which has been linked to pain and inflammation in other species. However, the test failed to reliably distinguish between horses with gastric ulcers and those without. Dr. Gustavo Ferlini Agne, from Adelaide University's School of Animal and Veterinary Sciences, explained that the result highlights the difficulty of identifying pain in animals that cannot communicate their discomfort. "Horses can't tell us when they are in pain, and signs of discomfort can be subtle, inconsistent, or easily overlooked," Agne said. "We need objective ways of identifying when a horse is suffering, particularly with gastric disease where the presence of a lesion does not necessarily tell us how much pain or discomfort an individual horse is experiencing." Of the 64 horses included in the final analysis, 59—nearly 92.2%—had gastric lesions. However, only 25% of the horses showed a measurable response in the blood-cell test. There was no significant link between the response and the presence of EGUS, and the test could not reliably distinguish between horses with and without the disease. The researchers also found no significant difference in facial pain scores between horses that responded to the test and those that did not. This is partly because EGUS is difficult to assess, as horses may show few obvious outward signs, and behavioral indicators of discomfort are not always consistent. EGUS is highly prevalent, particularly in the thoroughbred racing industry, with previous studies reporting gastric disease in 80% to 100% of racehorses for one major form of the disease. Dr. Agne emphasized that the ability to identify clinically important pain could have major implications for horse welfare, enabling better-informed decisions about treatment and management. However, the researchers stressed that the findings should not be interpreted as evidence that gastric ulcers do not cause pain. Instead, the results suggest that the immune response measured in circulating blood cells may not be sensitive enough to detect the effects of gastric ulcers, especially if the inflammation or pain is localized to the stomach. Agne said larger studies and horse-specific testing methods will be needed. "This is an important step because knowing what doesn't work is just as valuable as identifying a promising test," he said. The next challenge is to develop approaches better suited to horses, combining biological measures with careful assessment of pain-related behavior and inflammation. "Ultimately, the goal is to give veterinarians better evidence to recognize and manage presumptively painful conditions, rather than relying on guesswork."