A recent study out of Sam Houston State University, Huntsville, Texas, showed high starch meals can lead to inflammation, and feeds high in starch are not recommended for some horses, increasing the level of interleukin 1b, a potent inflammatory maker.

The publication The Horse said that this study found both overweight and older horses had higher levels of interleukin 1 b after consuming diets high in starch. The study involved two trials, and in the first trial, researchers divided middle-aged horses into two groups, those with normal weight and those that were overweight.

The horses were fed the same diet including, hay and steam-rolled barley. On day 14, they checked blood samples and found overweight horses had an immediate increase in interleukin while the normal weight horses only had increases in interleukin after 14 days.

Overweight horses were affected the quickest, but even normal horses had an increase in systemic inflammation following high starch diets.

The second trial involved two groups of horses aged 12-14 years old and 20-23 years old. Both groups were fed steam-rolled barley, hay, and a concentrate. After 36 days, blood testing revealed older horses had higher levels of increased interleukin il-1b compared to the younger horses.

These trials showed older and overweight horses had increased systemic inflammation compared to younger and fit horses. In humans, recent studies have shown that systemic inflammation like that caused by interleukin can cause neuroinflammation as is found with Alzheimer’s disease. Neuroinflammation is described as the brain's protective response to an inflammatory issue or challenge. 

Based on this study, feeding a high starch diet if your horse is overweight or is older is not recommended. Check with your veterinarian about your horse’s nutritional needs.