Sudangrass in the green growing stages can produce a horse urinary tract disease called cystitis syndrome or cystitis/ataxia (staggering). The disease is irreversible and believed to be associated with low levels of cyanide (prussic acid) in forage. Piper sudangrass is a low-prussic-acid variety and may be a good choice to minimize this problem.

Hay produced from sudangrasses will not likely cause cystitis/ataxia syndrome because prussic acid dissipates as hay cures. Sorghum pasture can also cause a problem for pregnant mares in the first three months of pregnancy, presumably because of prussic acid content. Foals can be born with contracted tendons, or mares can abort.

We must be cautious about high nitrate content in sorghum pasture and hay. The potential for it can be limited somewhat by cutting plants when they are growing under low stress conditions and on a sunny afternoon.

Sweet-stemmed sudangrasses and other sorghums that are relatively high in sugar also cause a laxative reaction in horses. If it is necessary to use sudangrasses, be sure to use a nonsweet starchy type and try to use other roughages as part of the ration.

Johnsongrass, which is a sorghum, and other sorghums can be high in prussic acid (cyanide), which can occur in any green plant and especially stressed ones. Rapid growth after a drought, drought or cold-stressed plants, and plants at and soon after frost are especially hazardous. Prussic acid does not occur in dangerous amounts in properly cured, dry hay. Prussic acid poisoning is not as severe a problem in horses as in cattle, but it can occur. Johnsongrass can also have a high nitrate content.

1. Alfalfa needs to be used with special caution to avoid overeating syndromes and blister beetle ingestion, which can cause colic and death.
2. Bermudagrass fungus can cause some problems in cattle. Its effect on horses is unknown, but they have been known to develop colic on bermudagrass pastures and hay.
3. Clovers, particularly red clover, can develop a mold that causes some problems in horses, such as slobbering or diarrhea.
4. Ergot is a fungus that occasionally grows in the seed head of dallisgrass, wild rye, Old World bluestems, and other grasses. It can induce blood vessel constriction and other associated problems.
5. Fescue toxicity syndromes are detailed elsewhere in this report.
6. German millet is a nitrate accumulator and can cause oral lesions.
7. Horses sometimes relish johnsongrass rhizomes, which cause possible sand colic from ingestion of soil dug up with the rhizomes. Johnsongrass also contains prussic acid. The rhizomes can be more than 10 percent crude protein.
8. Some pearl millets can accumulate nitrates and alkaloids.

1. colic
2. founder and other intestinal disorders
3. diarrhea
4. sand colic from eating rhizomes from forage such as bermudagrass and johnsongrass
5. excessive slobbering attributed to legume grazing

Potential Fence Toxicities
Treated wood rails and posts create potential toxicity reactions to cribbing horses. The CCAC treated wood commonly contains residue of chromate copper arsenate (CCA-C). Penta treated wood contains residue of pentachlorophenol. Both of these chemicals can potentially induce colic and other reactions. Caution prevails-if horses crib and then eat the treated wood, measures to prevent that behavior should be in force.

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