There is a web site that really helps me in deciding what to do but unfortunatley it leaves me with more questions than answers. Every horse owner should become very familiar with www.safergrass.org .
The most effective way to decide what to feed your horse is to have your hay analyzed by a laboratory to figure out what minerals are in it, and what is lacking. Then you supplement the minerals that are not in your hay, or what your horse is not getting enough of.
That's great, but typically we just buy enough hay to last us a month, and then get another source.... so it is not practical to keep analyzing and adjusting monthly.
My trimmer friend Sally Hugg has Cushings horses and she has analyzed a lot of hay samples from all over Northern California and Oregon.... She found trends! We are very low in zinc, copper, selenium, iodine, and a few other minerals. She worked with Uckele to develop a custom mineral blend that we can feed to our horses in Northern California that on average balances our hay and provides our horses with optimal levels of minerals.
I now sell this mineral to my clients for $50 per five pound bag.
Here is more information on CA Trace Plus:
"CA Trace Plus* is a concentrated trace mineral supplement designed specifically for horses on unsupplemented west coast grass hay diets. In addition to the balanced trace minerals, each serving provides 20 mg of biotin, 15,000 IU of vitamin A, 750 IU of vitamin E, plus additional lysine and methionine to support optimal hoof growth and strength. As an added bonus, horses on CA Trace Plus* develop lustrous, richly colored coats that resist sun bleaching and fading, even during winter. A common comment from customers after just a few months of feeding CA Trace Plus* is that their horses seem to "glow". Although I can make no promises or claims, it's not unusual to see the incidence of skin problems and allergies decrease over time while feeding CA Trace Plus*.
CA Trace Plus* is a custom formula and is not available in feed stores. The minerals are in a stabilized flax base to prevent clumping, but otherwise it is a highly concentrated product. Do NOT feed CA Trace Plus* with any other supplements containing trace minerals. If a commercial grain mix is fed, the daily serving of CA Trace Plus* may be adjusted. For best results, add 1/2 cup of ground flax daily in addition to the CA Trace Plus*. A small amount of moistened beet pulp or hay pellets makes a good carrier for the minerals. Some horses may be a little picky - start with just a pinch and increase the amount over a few days until the full 22 g daily serving is consumed. "
CA Trace Plus* has been formulated to save horse owners money over similar products. There is no fancy packaging to toss in the trash and no plastic pails to clutter up your feed room.
To Purchase CA Trace Plus, contact me at : firstname.lastname@example.org