I would use barrel bedding epoxy to close the holes. The stuff can be sanded down. You may have to put something on the inside of the horn to control how much glue goes into the horn, depending on how big a hole it. If the holes are located in the neck area, you might want to consider making a composite horn out of what is left, cutting away the neck that has the holes, and then finding another horn with a good nec that fits the base of your, cutting the new horn off to fit, and epoxying the two horns together.With scallups at the border of the two horns, this makes a very fancy styled horn out of what might have been a throw away. If the holes are all over the base of the horn, or on a couple of different side, then you might have to consider getting a new horn altogether. But you can cut strips out of your horn to use to make spoons, forks, combs, etc. All you need is an imagination, and maybe some idea from looking through some of the supplier catalogues to see what kind of horn impliments are being made and sold these days. I bought a horn spoon and fork at a rendezvous several hears ago. I also have a mug made from a large horn, with a wood base that was epoxied into the horn, and a strip of the horn extending up from the top edge of the mug and then steamed and bent over to form the handle of the mug.Drinking hot drinks out of the mug is not recommended, unless you like the smell and taste of horse hooves, but cold drinks seem to be okay. ( Beer?)