HAY AND GRAIN TOXICITY
Although there are many kinds of hay and grain toxicity, I will concentrate on the most common forms with which goat breeders have to contend.
Prussic acid poisoning, nitrate-nitrite toxicity, and aflatoxin result from extreme changes in weather conditions. Specifically, periods of heavy rainfall that are followed by very dry heat (or vice-versa) stimulate the development of these toxins in hay and grains.
PRUSSIC ACID POISONING
Also known as cyanide poisoning, prussic acid toxicity comes on suddenly, usually within 15 minutes of the goats' ingesting the toxic plant material, and is characterized by slobbering or frothing at the mouth and an increase in respiratory rate. Mouth breathing develops within five to fifteen minutes. The heartbeat is rapid and weak. Muscle twitching occurs quickly and spasms precede death. Muscous membranes are bright red, indicating a lack of oxygen transfer throughout the body that is necessary for continued survival. Death from respiratory paralysis comes during severe convulsions. The heart continues to beat for several minutes after struggling ceases and breathing stops. Blood often passes from the nostrils and mouth near the time of death. This entire process seldom takes longer than 30 to 45 minutes. If animals survive for more than two hours after the onset of signs of this illness, a high percentage of them will recover.
Ruminants are more susceptible to prussic acid (cyanide) poisoning than non-ruminant species, probably because the rumen releases larger quantities of hydrocyanic acid.
Cyanide-containing plants include Gregg's catclaw, acacia, catclaw acacia, devil's catclaw, mountain mahogany, iris, blue flag, common flax, western choke cherry, pine cherry, wild red cherry, bird cherry, fire cherry, wild black cherry, apple, Johnson grass*, sudan grass*, common sorghum*, poison suckleya, white clover, arrow grass, goose grass, sour grass, pod grass, maize, corn*. The plants indicated by an asterisk (*) are most commonly encountered by goat breeders in my part of the United States (Texas). Several of these crops are used as hay or grain feed.
Intravenous administration of sodium nitrite in a 20% solution is the treatment of choice for prussic acid poisoning. Because of the importance of speed in treating cases of cyanide toxicity, sodium nitrite and sodium thiosulfate are usually administered together. Some success has occurred by using oral preparations of sodium thiosulfate.
If you think that the goat's problem is prussic acid/cyanide poisoning, it is time to call the vet!
The risk of prussic acid/cyanide toxicity may be decreased by feeding commercially-prepared sack goat feed before animals are turned out to graze. Do NOT ever feed wet or moldy hay or grain to goats. Wet grain must be thrown out, but wet bales of hay can be broken and aired out until thoroughly dry, then used as goat feed . . . . IF the bales are lightly wet and all mold and mildew has disappeared.
Prussic acid poisoning can and does occur in crops which have NEVER been fertilized.
Few plants ordinarily have high nitrate content, although small quantities of potassium nitrite are found naturally in many plants. Under certain conditions, however, plants have the ability to accumulate large quantities of nitrates which are potentially toxic to goats. Toxic levels of nitrate are found in common pasture grasses and plants during periods of rapid growth, particularly when warm rains follow a very dry summer. Since soluble sugars are low at this time, nitrite accumulates in the rumen by slowing up the rate of metabolism to ammonia. Drought increases nitrate concentration in plants.
Crops grown on summer-fallow land often have a higher concentration of nitrates than land which is in continous production, since the latter conditions result in absorption of nitrates as the crops grow.
Nitrate poisoning usually occurs within several days after the hay has been moistened by rain, snow, or excessive dampness. Plants containing more than 1.5% dry weight potassium nitrate are lethal to goats.
The amount and type of fertlizer used on a field, as well as soil type, influences nitrate accumulation.
Nitrate-accumulating plants and grasses include pigweed, redroot, oatgrass, goosefoots, lamb's-quarter, Canada thistle, jimsonweed, barnyard grass, cockspur, bursage, silver leaf, poverty weed, white ragweed, wild sunflower, fireweed, cheeseweed, sweet clover, smartweed, Russian thistle, Johnson grass*, oats*, beets, rape, soybean, flax, alfalfa*, rye, sudan grass*, wheat* and corn*. The asterisked (*) products are often used to feed goats in Texas and other parts of the United States.
Deaths have also occurred from animals consuming water from shallow wells in certain areas of the Great Plains. An increase in the concentration of nitrates in stock tanks above that of the well water's nitrate level happens, often during freezing weather, perhaps by ground-water's being contaminated from heavily-fertilized soil or by barnyard runoff.
Signs of nitrate/nitrite poisoning appear suddenly. Difficulty in breathing is usually the first sign. Mouth breathing, weak and rapid heartbeat, low body temperature, extreme apprehension, anxious behavior, muscular weakness, and foaming at the mouth are symptomatic of this illness. The blood is brown colored because of the presence of methemoglobin; methemoglobin cannot bind oxygen. Death usually occurs within three to four hours; in extreme cases, the goat dies in convulsions within an hour. Goats who survive nitrate poisoning may have continual health problems associated with this toxic reaction. Respiratory distress in the form of labored, heavy breathing and occurences of interstitial pneumonia often happen. For those goats who recover from nitrate poisoning, the timeframe is 10-14 days, but pregnant females usually abort following recovery.
The most sensitive and reliable simple test for nitrites is the dephenylamine blue (DPB) test. Treatment for the illness is best accomplished by the administration of a 2% solution of methylene blue, which through a series of chemical reactions, allows the toxic methemoglobin to be converted to hemoglobin. A vet is needed for these procedures, which can be combined with the oral introduction of mineral oil to protect irritated mucous membranes. Stimulants usually don't help.
Goats fed rations containing grain (processed sack goat feed) can survive higher level of nitrates than animals maintained on pasture alone. The soluble carbohydrates in processed grain feed permits metabolism of nitrates without harming the goats.
Both prussic acid poisoning and nitrate/nitrite toxicity have several items in common. First, symptoms are remarkably similar and overlapping, with few exceptions, making diagnosis by a veterinarian essential. Secondly, producers should feed dry roughage (grass hay - NO sileage) and supplement their goats with a formulated pelleted goat ration. Breeders who insist on making their animals survive without supplements are destined to lose goats to problems like those described in this article.
Aflatoxin is a by-product of mold growth and is one of Nature's most potent carcinogens. When aflatoxin-contaminated feed is fed to goats, many health and performance problems result. Commodities in which aflatoxins have been detected include corn, peanuts, wheat, rice, cottonseed, tree nuts, milo, and milk. Corn is the crop that is most often associated with aflatoxins.
Once produced, aflatoxin does not go away, even if the molds die. There are two molds which are the major producers of aflatoxin, Aspergillus flavus and Aspergillus parasiticus. These fungi are found everywhere in the world. They are soil-borne but like to grow on the rich nutrients of seeds. Their toxins occur both in the pasture and when the feed is in storage. Weather-created stress, such as drought changing to heavy moisture conditions, help the fungi invade the plants. The fungi require moisture above 14% and temperatures higher than 75 degrees Farenheit. Feed in storage in closed, poorly-ventilated areas creates and maintains this deadly environment.
Because aflatoxin does not result in distinct disease symptoms, it is often not even suspected as being the cause of poor caprine performance. Aflatoxin suppresses the immune system, thereby allowing the goat to develop diseases that it would not likely have succumbed to had aflatoxin-contaminated feed not been fed. Aflatoxins can also be passed into milk by dairy goats.
The most accurate and cost-effective method available to detect mycotoxins, including aflatoxin, is the ELISA test (enzyme-linked immunosorbent assay). Quanta Lab in Selma, Texas (north of San Antonio on IH35) does this testing. Quanta Lab also tests for Prussic Acid and Nitrate/Nitrite toxicity. 1-210-561-5799.
Young goats are most susceptible to the effects of aflatoxin, although all ages can be affected. In all animals, aflatoxin can cause liver damage, decreased reproductive performance, reduced milk production, death in utero, tumors, birth defects, and lowered immune system function.
Periods of extreme weather conditions demand that goat producers keep a watchful eye on grain and roughages, whether they are out on pasture or being fed commercially-produced grain products. Extreme dry conditions interspersed with heavy rains should make you watch for toxic reactions of all types. When these conditions present themselves, testing of grains and hay must be done before feeding these products to goats. The cost of testing is minimal compared with the animal loss that may occur.
Suzanne W. Gasparotto, Onion Creek Ranch, Texas 9/11/16
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