Horses need only minute quantities of micronutrients to sustain bodily processes, including essential immune functions. As summarized in a recent review article*, a faulty immune system not only makes horses susceptible to infections they could normally fight off but also results in a decreased response to vaccination.
“When faced with a pathogenâ€”any disease-causing organism such as bacteria, fungi, or virusesâ€”the body recruits an array of infection-fighting cells, small proteins, and other molecules to battle the invading organism. When a horse’s diet runs short of key micronutrients, the cascade of events leading to the successful destruction of the pathogen is compromised,” explained Kathleen Crandell, Ph.D., a nutritionist at Kentucky Equine Research.
Based on currently available research, important micronutrients for optimal immune function include folic acid, zinc, iron, selenium, and vitamins A, D, and E. These micronutrients help bolster both the “innate” and “acquired” arms of the immune system. Key examples include:
- Deficiencies in vitamins A and D have been linked to changes to cells lining the respiratory and gastrointestinal tracts. Those layers of cells serve as the first line of defense against invading organisms; therefore, damage to these tissues can increase the risk of infection.
- Levels of vitamins A and D, as well as iron and selenium, affect the intestinal microbiome of horse. The microbiome helps fight gastrointestinal infections such as salmonellosis and clostridiosis.
- Micronutrient deficiencies decrease the efficacy of antibacterial peptides, which are small proteins circulating throughout the body to fight infection; reduce the ability of macrophages to destroy pathogens; and diminish the function of neutrophils, which are white blood cells that are among the first line of defense against invading microorganisms.
As summarized in the article, “micronutrient status has wide-ranging effects on most cell types involved in innate and acquired immunity, and deficiencies generally lead to dysregulation of immune function.”
“Kentucky Equine Research offers products to help horse owners ensure all macro- and micronutrient needs are met,” Crandell explained. A well-fortified feed will supply these nutrients in appropriate amounts so long as the recommended quantity is fed daily. If a feed is not part of your horse’s diet, or if you feed below the recommended amount, look for a high-quality vitamin and mineral supplement, such as Micro-Max. In Australia, choose Gold Pellet, Perform, or Nutrequin. Horses on all-forage diets also benefit from supplementation with a bioavailable source of natural vitamin E, such as Nanoâ€¢E.
*Smith, A.D., K.S. Panickar, J.F. Urban, et al. 2018. Impact of micronutrients on the immune response of animals. Annual Review of Animal Biosciences 6:227-254.