Question:  I have a 17 year old Friesian gelding. I started analyzing hay and following the balanced supplement program 3 years ago. At that time, Tabe (ta-ba) did not have cushings but since then tested positive and is being treated successfully with pergolide.

Tabe has had an ongoing problem with chorioptic mites in his feathers since he came to me at age 5. I have tried every possible solution; internal, external, natural, chemicals and wormers with no avail. I have shaved his legs and treated him. He gets relief for a short period of time but within a short time they always return. I know the mites are in the environment so it clearly is allergic/immune problem that he has. In addition, he has skin issues such as dry skin, psoriasis and sweet itch.
The following is the program I put Tabe on hoping to balance his needs and assist his immune system.

Magnesium 5 gm
Copper 2.449 gm
Zinc 4.668 gm
Salt 2 tbsp
Selenium 2 mcg
Vitamin E 2400 UI
Glutamine 30 gm
Chondroitin 5 gm
Spirulina 3 tbsp
Flax 6 oz
BioVet Equine Generator – Pre-Pro-biotic

I mixed this with either beet pulp or balanced cubes. The skin issues seemed somewhat better, however the mites did not go away or his reaction to the mites. His mane and forelock, that at one time were very full, have not grown back. Fortunately, he does have fantastic feet that grow very well. He began to become less and less interested in his meals. Also because I have to board him out, it is very difficult to have people follow through with his meals.

Currently he is not on anything but flax, hay stretcher and MVP Poulin grain. I know he is not getting all that he needs on this grain but until I figure out what you suggest. He is on hay stretcher because he started to have watery bowl movements, somewhat ball formations but watery and loose. The vet suggested the hay stretcher as it may help with the watery poops. It somewhat helped. Not sure but hoping that getting him balanced again will minimize this issue as well.

I wanted to see if there were any other ways to balance his diet other than with the powdered minerals that need to be weighted and mixed so meticulously. I am willing to do whatever is best but if the pelleted copper, zinc and/or magnesium are comparable I would like to go that route.

So my questions are as follows:
What would be your suggestions for the mite issue?
Would the U Balance Foundation be a good start and add copper/zinc, etc.?
What type of pre/pro-biotic do you recommend?
Would alfalfa pellets or cubes be ok to use for mixing supplements?

Dr. Kellon: Chorioptic mites plague many, many horses with long feathers on their legs.  There isn't necessarily anything wrong with his immune response.  In fact, since this mite does not bite or feed on blood, existing only on dead skin cells, it really doesn't interact with the immune system much at all.

The program you have him on looks good to me although depending on his weight you might need to adjust the spirulina and chondroitin dosages up to cover possible allergic reaction. 
Using U Balance Foundation as your base is an excellent approach and one I often recommend.  Determine your zinc and copper needs from your diet balancing then use the pelleted Poly Zinc and/or Copper to adjust to your needs.  It's also a good choice because the broad spectrum B vitamins and vitamin A will help with the skin issue.  The dryness/flaking can have a nutritional component or be related to irritation from the mite - or (most likely) both.
This mite has to be treated topically.  A wide variety of things have been tried but lime sulfur dip is the best:
The mites can persist in the environment in high numbers for several months once established so no surprise this problem keeps coming back.
For the issue of formed fecal balls with fluid around it, especially in horses this age, the problem is often a hay that is too fibrous.  You want a product with live yeast and digestive enzymes, like Quadra-Fac.

As for alfalfa pellets or cubes  for mixing supplements, y
es, just watch your amounts so that you don't upset the Ca:P balance.  If you move to pelleted supplements you won't have to worry about carriers as much.