The issue with cresty necks is not just how they LOOK but the fact that they increase the risk of founder, and trust me, you do not want that to happen to any horse you own. Cresty necks usually indicate a metabolic problem, especially insulin resistance, so horses with cresty necks should almost always be on a low starch diet. Sweet feeds are especially bad (anything "sweet"), and grass should be avoided (dry lots or a grazing muzzle). Feeding the lowest starch (NSC or non-structural carbohydrates) hay that you can find, and also the lowest NSC grain - below 10 if you can find it. Remission (or Quiessence) or any Magnesium/chromium supplement should help reduce the risk of founder, but diet is the main thing. You can also soak the hay to remove sugars - not just wet it, but soak it and then throw the water out. If you feed beet pulp be sure to use only the kind without molasses or else rinse it well before feeding. Managing an insulin resistant horse is a challenge but it can be done. Neck sweats DO help, and strong massage can also help.