What are the general characteristics of mycotoxins?
-produced by fungi which contaminate feedstuff
-often found in cereal grains or forage
-number of potential toxins is unknown
-presence of fungus does not always mean mycotoxins are present
What are the ideal conditions for mycotoxin production?
-warm temperatures
-high moisture
-plant stressed and/or damaged
What are the two conditions in which mycotoxins tend to be produced?
-plants in the field that undergo stress
-feed stored inappropriately
Which factors can contribute to plant stress?
-drought
-flood
-extreme temps
-insects
-herbicide damage
What are the characteristics of grain screenings and fines?
-chaff and broken/damaged bits left over after cleaning
-contain the highest amounts of mycotoxin contamination
What are the characteristics of mycotoxin detection?
-lab sensitivity is so good that some mycotoxin levels are typically found regardless of if they are causative
-action level is the conc. at which mycotoxins are considered unsafe
-acceptable level is detectable concentrations below action levels for a specific product
-grains for human consumption have lower tolerance than those for animals
How does mycotoxicosis differ from mycosis?
mycosis: disease caused by fungal infection
mycotoxicosis: disease caused by mycotoxin exposure
Which animals are more and less susceptible to mycotoxicosis?
-ruminants are less sensitive
-monogastrics are more sensitive
What are the three factors contributing to mycotoxicosis severity?
-concentration
-duration of exposure
-species
What are the general characteristics of aflatoxins?
-found primarily in corn; also peanuts, cottonseed, and cereal grains
-fungal invasion of seeds/kernels and growth and toxin production
-occurs when plants are damaged and then exposed to warm, humid conditions or drought
What is the pathophysiology of aflatoxins?
-aflatoxin B1 (AB1) is present in highest concentration
-preformed aflatoxin is ingested
-aflatoxin goes to liver and caused direct damage to proteins, enzymes, and DNA
-result is cellular necrosis, immune suppression, mutagenesis, and neoplasm
-AM1 is excreted in milk and infiltrates muscle tissue
What are the clinical signs of acute aflatoxicosis?
-sudden death
-prolonged prothrombin time
-hemorrhage
-petechiation
-bloody diarrhea
-anorexia
-rumen atony
-ataxia
-tremors
-abortion
-liver failure
What are the clinical signs of chronic aflatoxicosis, which is more common?
-poor growth
-poor milk production
-poor feed conversion
-rough coats
-ill thrift
-immunosuppression
-hepatic fibrosis
-infertility
-carcinogenesis
Which species is affected at the lowest concentrations of aflatoxins?
poultry
What are the minimum database tests for aflatoxicosis?
*CBC:
-low RBC count
-low hemoglobin
-thrombocytopenia
*chem (liver failure):
-hypoalbuminemia
-high ammonia
-high bile acids
-high bilirubin
*chem (direct liver damage):
-high AST, ALT, SDH, GGT
Which conditions make an animal more susceptible to aflatoxins?
-growing animals
-high production animals
-poultry
-young piglets
-diets lacking protein, selenium, and/or vitamin E
How does the exposure level of aflatoxin affect the presentation?
*low conc:
-hepatic insult and suboptimal growth in piglets
-decreased performance, depression, ataxia, and resp. infections in calves
*moderate conc:
-affects mature horses, cattle, and swine
-causes hepatic damage
*high conc:
-affects animals regardless of species or age
-causes coma, lateral recumbency, hepatic failure, and death
What is the diagnosis of aflatoxins based on?
-clinical signs
-lesions
-toxic concentrations in the ration
Which samples are taken for aflatoxin testing?
-5 kg (10 lb) of feed that is randomly selected and represents as much of the storage conditions as possible (perimeter and center, moving flow ideal)
-liver and kidney tissue samples
What are the steps to treating aflatoxicosis?
-remove potentially contaminated feeds and replace with healthy feed
-supplement with trace minerals and free radical scavengers
What are the prevention steps for aflatoxicosis?
-store grains at less than 12% moisture
-clean grains/screen before storing
-use water tight grain bins
-ammoniation of feed to reduce fungal colonization
-adding binders
What are the two types of ergot alkaloids toxicities?
*fescue toxicosis:
-infected fescue that produces ergovaline
*ergotism:
-infected small grains that produce ergovaline
What are the three pathologies of ergovaline?
-vasoconstriction
-hypoprolactemia
-fat necrosis
How does ergovaline cause vasoconstriction?
-activates alpha1-adrenergic and serotonin receptors
-inhibits D1-dopamine receptors
-results in vasoconstriction of small vessels and poor peripheral blood flow
-effect is exacerbated by cold weather; leads to ischemia and necrosis
-in hot weather, animals cannot dissipate heat correctly
