This is a relatively new area of scientific investigation in equine health. Lori Warren, PhD, PAS, equine nutritionist in the Department of Animal Sciences at the University of Florida, presented on the topic at the 15th Annual Mid-Atlantic Nutrition Conference, held in Hunt Valley, Maryland, on April 6, 2017.
The Immune System
The immune system has two main components: innate and adaptive. The innate immune system is the general, first line of defense against pathogens (disease-causing organisms) or trauma. You’re born with it, and it has no specificity or “memory.” The adaptive immune system learns to “remember” specific pathogens so it can respond to them faster. Antibodies resulting from vaccination are the most well-known adaptive immune response. The immune system has a lot of redundancy, so if one part fails, there’s often a backup. Innate and adaptive immune systems work together to coordinate a response.
The equine industry in general is interested in things that will improve overall horse health, and owners spend lots of money on nutritional supplements. But do they really help boost immunity? It’s possible.
“The processes of digestion and immunity are interwoven,” Warren said. “Over 70% of immunity is associated with the digestive system.”
Which Nutrients Do What?
The challenge lies in understanding which nutrients play a role in supporting the immune system. To study the immune system, researchers must challenge its needs. Additionally, it’s difficult to study healthy horses, because their immune systems are presumably functioning normally. Therefore, it makes more sense to study horses that might have compromised health (e.g., by way of transport stress, weaning stress, or inflammatory agent exposure) and evaluating their dietary response to a stressor.
Just about all nutrients are important to the immune system, including protein, fat, vitamins, and minerals. Researchers have studied the effects of fat and fiber on immune health, and omega-3 fatty acids are promising for anti-inflammatory properties with respect to osteoarthritis and inflammatory airway disease. Functional fibers (prebiotics such as beet pulp and oat hulls) help bacteria in the gut produce volatile fatty acids and reduce pathogenic bacteria.
More research, however, needs to be done to determine the effects of probiotics on digestive health, Warren said.
Nutrition research focusing on immune function is relatively new in horses, with increased interest in the last 10-15 years. It’s unlikely that diet can improve normal immune function, but horses with compromised immune systems might benefit from the addition of certain nutrients. More research is needed to draw definitive conclusions, because stressed or immunocompromised horses’ nutrient requirements are still unknown.