Horses Health - Toxic Plants Part 3

Plants That Can Seriously Damage Your Horses Health

It really is lucky that horses don't find most these plants very palatable. However, there are exceptions and sometimes horses will eat highly toxic or lethal doses, even when forage is adequate. That's why summer is a good time to explore your horse pasture to be sure toxic plants are kept out of your horse's diet. Remember that some of the plants I have covered are evergreen, so they will be around in the fall, winter and spring too.

This issue will cover:

• Fiddleneck and Related Plants
• Crotalaria Species
• Senecio Species
• Chokecherry and Wild Cherry (Prunus)
• Sorghum and Sudan Grass
• Bermuda Grass
• Black Locust
• Oak Trees

Again I need you to know that I have not written the following – I am not a Vet or a plants man, so I have copied this information simply to make it easy for you to read. I would not re-write it because I was afraid of getting something wrong that may prove fatal to your horse, so I make no apologies for copying this.

Fiddleneck and related plants

Several members of the amsinckia species have been linked to causing cirrhosis of the liver. These plants include fiddleneck, tarweed, yellow burr weed, fireweed and buckthorn, which are predominantly found in the semi-arid regions of Idaho,Washington, Oregon and California. The plants appear in late winter and early spring. The seeds are the most toxic parts of these plants and fortunately the mature plants are unpalatable to most horses. Most instances of poisoning occur when mature amsinckia species are bailed in early cuttings of hay or when contaminated grain was threshed for horses. Some poisonings have occurred when horses were pastured on wheat stubble in contaminated fields.

Cirrhosis causes hardening and eventual metabolic shutdown of the liver. The liver can no longer filter out toxic wastes which, among other things, produces disturbances of the nervous system. Affected horses have been known to walk aimlessly for miles, running into objects in their path rather than go around them, pressing their heads into solid objects and occasionally becoming frenzied when they cannot continue. Oftentimes death results from the horse getting hopelessly entangled in a fence or literally walking over the edge of a cliff or ravine.

Other behavioral abnormalities include recklessness, charging, lack of coordination, circling, staggering, "dragging" of the hind limbs, which have been described as the "sleepy staggers". The horse may also appear listless, hang its head and acting sluggish or depressed. Signs of colic may be present, which may include straining, diarrhea and rectal prolapse. Small foul smelling ulcers may appear in the mouth.

The chronic patient will become a poor keeper, show yellow membranes around the eyes and mouth, produce a rough coat and eventually become anemic and die. Fortunately healthy horses need to consume amsinckia plants over a period of time before enough liver damage occurs to produce symptoms. Unfortunately, once cirrhosis of the liver develops, it is for all practical purposes irreversible.

Crotalaria Species
Crotalaria, predominantly found in the south and southeast, has been the cause of many horse losses. Known as wild pea, rattle box and rattle weed, crotalaria has been intentionally planted as an agricultural cover crop to enrich the soil from the Atlantic seaboard, west into Texas. Two species, crotalaria sagittalis and crotalaria spectabilis, are particularly toxic and produce the same effects as fiddleneck.

Senecio Species
Senecios comprise one of the largest genre of plants in the midwest and western US.Not all species are poisonous, and of those which are, only a few contain enough alkaloids to cause problems in horses. Those which do can produce the same kind illness as fiddleneck. Senecio jacobaea is particularly toxic. In the Nebraska region, "walking disease" is caused by senecio. In the Pacific Northwest, the disease is commonly called "Hard Liver Disease" or "Walla Walla Walking Disease."

Other species such as ragwort, common groundsel and "Stinking Willie" are generally considered toxic, however their alkaloid content seems to be less than senecio jacobaea.

Chokecherry and Wild Cherry (Prunus)
Chokecherries, growing in bushes up to 12 feet high, are popular for their jelly producing berries. They are common throughout the US, often found along roadsides or creek bottoms. Unfortunately the leaves, which are particularlytoxic when stressed or wilted, as well as the bark from chokecherries and wild cherries are cyanide producing. Death in horses can occur literally in minutes after the horse has ingested the leaves. The horse will appear to have trouble breathing, show flared nostrils and lose bowel and urinary control. Lack of coordination and trembling may also appear, along with agitation. A severely poisoned horse will drop to the ground, kick a few times, then die. Poisoned horses can be saved, however usually veterinary help cannot arrive in time as the effects of cyanide poisoning progress rapidly.

Sorghum and Sudan Grass
Sorghum and Sudan Grass, both of which can be effective as livestock feed when grown, harvested and cured correctly, can produce cyanide poisoning when improperly managed. After a hard frost or trampling, prussic acid can build up in new growth which grazing horses are likely to seek out. The effects of this poisoning is the same as with choke cherries.

Other problems associated with grazed or improperly baled sorghum and sudan grasses include urinary tract complications, causing thick and viscous urine and bladder infections. Signs of such problems may appear as buildup inside the horse's hind legs. If left untreated, the infection can become fatal. Pregnant mares may abort or give birth to deformed foals.

There are species of sorghum which are developed especially for animal feed, and we have fed them with great success. However, when feeding sorghum to horses, one should be certain what kind of sorghum is being grown and that the grower knows how to properly manage, cure and bale the crop. Unless you really know what you are doing, letting your horse graze on growing sorghum or sudan grass can be a risky proposition.

Bermuda Grass
Berumuda grass can be good feed for horses, however in certain climates a harmful fungus called ergot can be present and which appears as small brown or black nodules on the bermuda grass or dallis grass seed heads. When consumed, a condition known as "Bermuda Grass Shakes" or "Dallis Grass Tremors" can occur, producing such symptoms as lack of coordination, tremors, strange head movements and tongue rolling, and in severe cases, paralysis.

Once the tainted forage is discontinued, horses may recover rapidly, virtually overnight to several days. Pregnant mares, however, may abort.

Black Locust
Horses tied to black locust trees or black locust posts and who have chewed on the bark can become poisoned, becoming very ill in just a few hours. Symptoms include loss of appetite, general weakness and depression.Symptoms of a mild colic may also be present. Horses can ingest enough bark to prove fatal, although most recover after several days or weeks.

Oak Trees Horses have been known to binge on acorns, particularly if they are hungry and are not used to having them around. Acorns and many oak leaves are high in tannin. It is relatively easy for a horse to ingest several pounds of acorns in a relatively short period of time leading to an unfortunate overdose. Well, that’s it from me on poisonous plants. I would suggest that you keep all 3 of these newsletters handy just in case. In fact I have printed them off and am going on a walking tour of my fields and local pastures and see what I can spot that is potentially dangerous. Then I will report it to owners, and if its in my pastures, take appropriate action to ensure that my horses aren’t hurt by it. I would suggest that you find time to do the same.

From the author: Roger Bourdon has written a book on Introduction To Horsebackriding and Horse's Health. (Article Adapted by All About Horses)

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