So I like to carefully cruise through the official forums for random tidbits of info. Mostly I still to the dev tracker. Anyways, I saw this little nugget of info and thought I would share.
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So basically, mounds and feeding your mount is going away. You will have mount "skins" that you can use via your collections screen. The skins are (as far as I understand) account wide. The riding skill is now going to replace feeding each horse individually. Instead, you will go to the stable master, and take a daily riding lesson to improve one of the three areas. From what I understand, you can get max skill in all areas. In transition, they are going to take the max obtained horse stat for all your individual characters horses and apply it to that characters riding skill. So, my main guy has three imperial horse. One is all speed. One is a mix of speed and bags, and one I have no clue what the heck is on him. Come 1.6, I will get 50 points in speed, and 30(ish) points on bag space. The 30 bag space comes from the oats I fed to my mixed horse, and the 50 speed comes from the horse I fed pure apples. My sorc on the other hand has 2 horses. One is the 42k speed horse with full apples. That will grant him 60 speed. He also has a full bag space imperial horse. That will grant him 50 bag space. So, if you have the extra cash, it will be beneficial to you to get some new horses, and feed them exclusively one food. Essential this will be the same as "training" your skill 3 times per day versus once per day when 1.6 comes out. If you REALLY have the extra cash, get one of each of the three 42k horses for that extra boost in stats. Me, I'm just going to get more imperial horses.
TL:DR Horses are changing. To get a head start, you should have three horses and feed each one ONLY 1 food type to get a head start on the new system.
Hope I didn't cause any confusion, but I am sure I did. Feel free to post questions and I will answer to the best of my abilities.