Feed related toxins

• Often toxins unknowingly infest common feedstuffs
• Awareness of what toxins are and how they work can prevent poisonings

Occasionally feeds that are normally considered safe and are commonly fed to livestock can harbor toxins that cause illness. Knowing how these toxins work and how they infect feeds can help alleviate symptoms and prevent future poisoning episodes from occurring. 

Botulism

• caused by a toxin produced by the bacteria Clostridium botulinum
• toxin is considered one of the most potent poisons known
• Clostridium bacteria are anaerobic and spore-forming, meaning they can lie dormant for long periods of time. 
• spores are very resistant to heat, drying and freezing conditions
• symptoms include: weakness, abnormal facial expressions, drooling, nerve, cardiac and respiratory paralysis, death
• symptoms may appear 1-7 days following ingestion of toxin
• Clostridia are often found in carcasses, so any carcasses baled in hay or packed in silage can contaminate feed.  Improper burial or disposal of carcasses can also be a cause of contamination  

Bovine Spongiform Encephalopathy (BSE, "Mad Cow Disease")

• a neurological degenerative disease in cattle
• has been detected in the U.K. and a few other countries, but not in the U.S.
• can be contracted by feeding animal protein byproducts containing brain or spinal tissue from infected animals (ruminants only)
• visit http://www.aphis.usda.gov/lpa/issues/bse/bse.html for more detailed information  

Ergot Poisoning

• caused by Claviceps spp., a parasite fungus
• attacks and replaces seeds in grasses and cereal grains
• effects of toxicity are cumulative
• acute symptoms include paralysis of limbs and tongue, trembling, frequent urination, abortion
• chronic symptoms includegangrene, sloughing of hooves, ears and tail 

Fescue Toxicity

• occurs when the fescue plant becomes infected with the fungus Acremonium coenophialum
• fungus is an endophyte, living within the plant
• endophyte-free seed is available for planting
  horses tend to be especially sensitive
• symptoms include: decreased conception rate, poor gains, sloughing of hooves and tail, poor hair coat & decreased heat tolerance

Johne's Disease

• caused by the bacteria Mycobacterium paratuberculosis
• occurs when manure from infected animals contaminates feed
• see Johne's an overview  for further details
• symptoms include: chronic diarrhea and emaciation that do not respond to treatment  

Listeriosis or "Circling Disease"

• caused by the bacteria Listeria monocytogenes
• found in aerobic, mildly acidic (> pH 5.4) conditions, such as top layers of silage piles, or improperly packed silage
• vaccines are not available in the U.S.
• can be contracted by humans
• symptoms include fever, depression, abnormal gait, leaning, progressive paralysis and death  

Mycotoxins

• caused by many different types of molds that may grow either in the field or during ensiling
• see Molds and Mycotoxins for further details
• symptoms include: feed refusal, diarrhea, reproductive failure, brain damage and death  

Neosporosis

• caused by protozoan Neospora caninum
• occurs when contaminated dog feces get into the feed
• see Disease Specific Biosecurity part 2 for further details
• symptoms include: abortion outbreaks, reproductive failure  

Nitrate Poisoning

• caused when plants accumulate excessive levels of nitrate
• often a problem during drought conditions, especially with nitrogen fertilization
• levels exceeding 1% nitrate are dangerous
• grasses that tend to accumulate nitrate include: oats, wheat, barley, sudan grass and corn
• symptoms include: weakness, labored breathing, abdominal pain, coma 

Prussic Acid Poisoning

• certain plants tend to form HCN (prussic acid) from naturally occurring compounds
• Environmental conditions, such as killing frost, rapid growth after a period of drought or application of certain herbicides, allow HCN to accumulate to toxic levels
• grasses often affected include: Johnsongrass, sorghum sudangrass, sorghum-sudan hybrids & wild cherry
• HCN levels tend to decrease over time
• HCN interferes with oxygen transfer in cells, causing animals to suffocate
• symptoms include: excessive drooling, panting, tremors, staggering & death 

Salmonellosis

• there are over 2000 serotypes of salmonella ´
• often present in herds at a subclinical level
• can be spread to humans
• herd outbreaks are more likely caused by a plant protein or fat or animal fat, than by manure contamination
• infections tend to be resistant to antibiotic treatment
• practices that are recommended to reduce contamination of feed with salmonella include: sourcing feed from a company that employs salmonella control practices, cleaning and disinfection of feeding equipment, separation of feeding and manure handling equipment, rodent and bird control and ensuring cleanliness of water supply
• symptoms include: severe diarrhea, dehydration, abortion, arthritis and pneumonia