Horse health bar not displaying un-filled health after relog

When riding a horse which has lost some of its health, if you reload the world or disconnect from a Realm and connect again the horse health bar will only show the remaining. Any health is had lost will not appear as greyed out as it usually would, it appears as though the horse now has less overall health. This health does regenerate however and as it does each of the original health points are again visible as they are regenerated.