For feeding HYPP horses.
Beet pulp is very low in potassium--about .3%--and high in fiber and calories. It makes an excellent feed for HYPP horses. If you don't want to feed the horse so much grain, then you can feed a combination of grain and soaked beet pulp, then feed the amount of hay that is equal to the combination of grain and beet pulp. That will put you just under the 1%. The beet pulp is low in protein and therefore doesn't make them "high". The only downside to that diet is that the beet pulp and the alfalfa are high in calcium (where the grain is high in phosphorous), and while mature horses can tolerate an imbalance, youngsters will get contracted tendons from too high a calcium level that isn't balanced with phos. Therefore, I add 1-2 cups of soybean meal to the mix to increase the phos. level. It also raises the protein some, which if you are feeding young horses or broodmare in that last part of gestation or during nursing, is just fine. BTW, not balancing the calcium and phos in the latter part of pregnancy will cause the baby to be born with contracted tendons, too, so you really want to be careful about that (this is true whether HYPP is an issue or not).
Most of the literature will tell you to feed grass hay instead of alfalfa, but this is misleading. Several horses in Oregon that had never had any problems but were found to be HYPP+ when this first came out found this out. Their owners switched to grass hay (having to feed considerably more of it to get the same calories as the alfalfa they had been feeding), only to have their horses start episoding. Where alfalfa is 1.5% potassium, it turns out that the level of timothy hay is about 1.8% and orchard grass (the most abundant in the Willamette Valley) is 2.59%! When they started feeding these hays, and increased the amount by two to three times to get the same calories, they pushed the total dietary potassium right thru the roof and the horses episoded. When they went back to their previous levels of alfalfa, the horses did fine. Oat hay is only slightly lower in potassium than alfalfa, (1.35%), but by the time you increase the amount you feed, your levels are back up there.
Two other things to consider with HYPP horses--use WHITE (plain) salt, not the "mineral" or "protein" blocks. Also, DO NOT use commercial electrolytes. All of these contain potassium chloride, instead sodium chloride, which is table salt. If it is felt that the horse needs electrolytes (as in REALLY hot weather), hang a second bucket of water in the stall that contains a package of sweetened Kool Aid and a couple of tablespoons of table salt. This is sugar and sodium chloride. Even with non-HYPP horses, electrolytes should always be an OPTION, not forced as the level of potassium in these solutions can push even an N/N horse into muscle spasms that are the hallmark of HYPP.
Another product that should be avoided is molassas on the grain. It is high in potassium, and really not necessary.
Virtually all HYPP horses do much better on pasture or with as much turn-out as possible, and I know of many HYPP horses who can graze on alfalfa fields or eat their fill of alfalfa with no grain as long as they are out grazing. The movement of grazing stimulates their bodies to keep the potassium levels in check.
In managing the positive horses, it is basically common sense. Keep them well watered, especially when traveling, and keep the diet in balance. I do keep clear Karo syrup on hand and if I see the signs of an episode, or if I am going to put them under a major stress (like anesthetic), I will give them one or two 60cc syringes of it orally. I also keep the acetazolomide on hand and will give a dose if there is a stress (6-8 tabs per twelve hrs is the normal dose). I have never had a horse that had to be maintained on the med, but if you run across one that has, balance the diet and then wean the horse off the med (1 tablet a day, alternating dosages--1 less am day one, 1 additional less day 2, etc.), so the body has a chance to adapt to the new demands.
The biggest factor, after stress, that seems to affect these horses is humidity rather than heat. The mare we had over here had no trouble with the heat last summer--100+ for 30+ days. On those days, I would offer the Kool Aid mix along with all the water they could drink and there should be no problem.
Written by Penny Steward