We humans have a huge diversity of individual dietary preferences. Some have a raging sweet tooth, others prefer salty or spicy, love or hate specific vegetables, etc..
It’s not as complicated for horses. Their instinctive taste preferences are geared toward survival. Try as you might, you won’t be able to create an acquired taste for sushi in a horse.
Calories are the first priority in survival. Every study on horses or other herbivores has shown preference is linked to simple carbohydrate content. High carbohydrate also usually means low fiber (thus high digestibility) and often high protein as well.
The only factor consistently associated with selection of bark for stripping is the carbohydrate content.
Simple carbohydrate, sugars and starches, are the most easily utilized calorie source. Beyond this, there are factors of aroma and possibly texture. Put a pile of freshly cut young grass next to one of straw and you know what the horse will select. Alfalfa vs grass hay is also a predictable selection.
These preferences are virtually universal. Find me a healthy horse that will turn down the offer of a freshly picked mature ear of corn, or a peach. It won’t happen.
Since starch has virtually no taste or aroma, horses basing their choices on simple carbohydrate content are selecting for sugar. The simple sugar content (e.g. like table sugar or fruit sugar) in grasses is relatively low but more complicated plant sugars with less intense flavors may also appeal to horses.
Horses habituated to sweet feed may be difficult to switch to plain grains, brans or beet pulp. Things that other horses find very appealing they will turn down because they have come to expect and look for the more intense sweet flavor. The best way to deal with this is to very gradually replace the sweet feed with the new food item.
When a horse is just picky in general, suspicious of anything new, if a medical cause has been ruled out you can probably experiment to find a taste and aroma that the horse finds irresistible. Apple, banana, peppermint, cherry and fenugreek are all favorites. Red beet root (not sugar beet) powder works for many. Coconut oil has wide appeal but is solid at room temperature and difficult to work with unless you use the combination of soy and coconut in CocoSoya oil. Even barn cats are drawn to this!
Liquid forms like CocoSoya are especially useful because they can also be sprayed in a light layer on hay. Another helpful one is “alfalfa tea”. Take alfalfa hay or a high quality, green alfalfa cubed hay and put it in a gallon glass jar. Fill the bottom 1/4 then top off with water and put into a sunny window until an aromatic green tea forms. Store in the refrigerator.
Horses have good instincts for identifying food items that are at least highly likely to provide them with easily utilized calories. When you know the common preferences, you can utilize that to convince them to clean up foods they might otherwise think are not appealing.
Eleanor Kellon, VMD