Thanks easy e… yea, now I remember… .cholesterol for animals, ergosterol for plants. 
I like nutrition and biochem courses… finally, chemistry that makes sense! 
Oh yea, and of course along with the horse, every other animal in horse family (donkeys, zebras, whatever).
And cows in barns that are not in pasture (or even those in pasture, depending on the type of grass) may get some supplements not available on the feed or type of grass. Perhaps a “treat” with more calories, and some minerals that work as co-factors that are lacking on their diet (due to type of soil, weather, vegetation, etc.).