Horses are living longer, healthier lives thanks to improvements in veterinarian care and advancements in biology and chemistry. The new challenges with caring for older horses is the potential of more years of poor health. Understanding how nutrition supports an older horse’s immune system can help keep senior equines healthy.

A better understanding of the mechanisms leading to a decline in physiologic function with age would provide new predictive biomarkers and potential therapeutic targets. 

It has been well-documented that the aged, including horses, have increased susceptibility to and prolonged recovery from infectious diseases, poor responses to vaccination, and increased incidence of various cancers. Furthermore, it is now accepted that chronic inflammation (inflamm-aging) is a major underlying condition of many age-related diseases, such as atherosclerosis, arthritis, cancer, diabetes, osteoporosis, dementia, vascular diseases, obesity, and metabolic syndrome. 

In anti-aging research, much attention is focused on nutritional interventions as practical, cost-effective approaches to mitigating this age-related breakdown in immune function. These natural dietary compounds found in a variety of fruits, vegetables, nuts, and seeds are promising candidates in helping to combat the effects of aging. They possess broad biological activities: anti-oxidative, anti-inflammatory, detoxification, regulating signaling pathway, and modulation of enzyme activities.

Since aged horses (>20 years) have increased levels of inflammation, and treatment with long-term use of non-steroidal anti-inflammatory drugs (NSAIDs) such as flunixin meglumine and phenylbutazone can pose health problems, we are interested in nutritional interventions to counteract this process. 

Flavonoid (quercetin) and polyphenolic compounds (curcuminoids, resveratrol, pterostilbene, and hydroxypterostilbene) were compared to phenylbutazone and flunixin meglumine to determine differences in equine cytokine production in cell culture. White blood cells from aged horses were isolated and incubated overnight with each compound or NSAID at multiple concentrations. Inflammation production was measured when cells were stimulated.

At varying doses (measured in micromolar units [μM]), each of the compounds and NSAIDs significantly reduced cellular inflammation: curcuminoids (20 μM), hydroxypterostilbene (40 μM), pterostilbene (80 μM), quercetin (160 μM), resveratrol (160 μM), flunixin meglumine (40 μM) and phenylbutazone (>320 μM). Interestingly, curcuminoids at a concentration of 20 μM reduced inflammation to the same level as higher doses of flunixin meglumine (40 μM) and phenylbutazone (>320 μM). All-natural compounds outperformed phenylbutazone by being effective at lower doses.

This preliminary research has led to two studies using aged horses to determine: 1) if a relationship exists between circulating vitamin and fatty acid levels to systemic inflammation and muscle mass, and 2) if anti-inflammatory supplementation affects immune responses to vaccination. These are preliminary steps to identify effective nutritional intervention regimens to improve the function of the immune system in the aged horse.

By Amanda Adams, DVM and first published in the Equine Disease Quarterly.