Flavor Favorites For Horses
If your horse turns her nose up at carrots, try a banana, or better yet fenugreek. In a taste testing trial of 15 flavors, horses picked fenugreek as their favorite.
Eight equine taste testers started off with unflavored pellets of cereal meal. Two horses found these unappealing, refusing to finish their meal.
Over the next several days, the horses went on to sample the concentrate ration in 15 different flavors of fruits, herbs and vegetables. Three of these flavorings were also rejected by some of the testers.

Carrots aren't a horses' favorite flavor.
Out of the dozen flavors all horses approved of, eight got gobbled up the fastest. Further sampling of these revealed fenugreek to be the overall favorite. It was followed by banana, cherry, rosemary, and cumin. Carrot, came in a mere sixth, trailed by peppermint, then oregano.
The taste testers were all horses stabled in the United Kingdom. Researchers who documented the results based their interpretations of the horses' flavor assessments on how quickly and how much of the feed was eaten.
Reference
D. Goodwin, H.P.B. Davidson and P. Harris. 2005. Selection and acceptance of flavours in concentrate diets for stabled horses. Applied Animal Behaviour Science. 95(3-4): 223-232.