A staple in my feed room. Tried and true.
Have a senior lab panel done on your oldtimer and see if they're anemic. Very old horses tend to not produce enough red blood cells and this product can make a big difference in how they feel. I've had quite a few horses live super long lives...lost my mare at almost 40 last fall. Red Cell is a staple at my barn to keep my old friends living happy, healthy lives.