SZENT ISTVÁN UNIVERSITY
FACULTY OF AGRICULTURAL AND ENVIRONMENTAL SCIENCES
DEPARTMENT OF NUTRITION
Course booklet
Miklós Mézes Ph.D., DSc., Professor of Nutrition
GÖDÖLLŐ
2004
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Main topics
1. Terminology of toxicology
2. Basic mechanisms of xenobiotic transformation
2.1. Biological oxidation and the oxidative detoxication
2.2. Mechanism of glucuronoid formation
2.3. Glutathione in xenobiotic transformation
2.4. The cytochrome P450 system
2.5. Metals and methallothioneins
3. Chemical mutagenesis and the DNA adduct formation
4. DNA repair mechanism
5. Systematic toxicology
5.1. Amino acid toxicoses
5.2. Vitamin toxicoses
5.3. Lipid peroxidation and lipid peroxide toxicosis
5.4. Metal toxicoses: arsenic, cadmium, copper, iron, iodine, lead, mercury, phosphorus,
sulphur, selenium, zinc
5.5. Sodium-chloride toxicosis
5.6. Nitrate and nitrite toxicosis
5.7. Toxicoses caused by alkaloids and glucosides
5.8. Phytoestrogens and photosensibilising compounds
5.9. Insecticide toxicoses
5.10. Herbicide toxicoses
5.11. Rodenticide toxicoses
5.11. Mycotoxicoses
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TERMINOLOGY OF TOXICOLOGY
TOXICANT: those organic and/or inorganic materials/compounds which are cause toxic
symptoms or toxicoses
TOXIN: biologically derived toxicants (e.g. snake venom, plant toxins etc.)
TOXICITY: amount of toxicant which cause clinical signs of toxicosis
ADDITION: two (or more) different toxicant act through the same organ and those effects
manifested additionally
SYNERGISM: two (or more) different toxicant strengthen the effect of other(s)
(in that case the toxic dose can be smaller)
ANTAGONISM: one toxicant inhibit or eliminate the toxic effect of an other one
(toxicity can be decrease and toxic dose increase)
ANTAGONISM: absorption capacity  degradation / excretion capacity
TOLERANCE: gradually lower reactivity in the case of repeated exposure
DOSES:
LD50 : 50 % of approximate lethal dose ( e.g. mg/kg b.w. p.o.)
MNTD: maximal non-toxic dose - no detectable clinical signs
MTD: maximal tolerated dose - toxicosis without mortality
ACUTE TOXICOSIS: clinical signs appeared within 24 hours
SUBACUTE OR SUBCHRONIC TOXICOSIS: clinical signs appeared between 24 hours and 180
days
CHRONIC TOXICOSIS: clinical symptoms and toxic effects appeared later than three months
CHRONICITY FACTOR: ratio of acute and chronic LD50 value
in case of tolerance:
e.g. KCN
CF: 0.04
same:
e.g. coffein
CF: 1.30
in case of accumulation:
e.g. warfarin
CF: 20
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METABOLISM OF TOXIC MATERIALS
main route of metabolism : lipid-soluble  water- soluble
excretion - kidney  bile juice
changes of chemical structure
PHASE 1. : formation of polar groups (oxidation,reduction, hydrolysis)
PHASE 2. : biosynthetic conjugation - glucoronoids, acetylation, glutathione-complex formation,
Gly-complex formation
PHASE 3. : excretion through blood circulation and kidney to urine
excretion through bile juice to GIT and to feces
Basic mechanism of xenobiotic transformation
Question: Why the higher vertebrates synthetise those enzymes which can metabolise xenobiotics
because most of those compounds - synthetic molecules- are not present in the
environment ?
Answer: Animals and plants are produce some secondary metabolites (toxins) for their defense mechanism (e.g mycotoxins - phytopathogenic fungi , hydrogen peroxide - unspecific
immune response)
Animals have been developed during the evolution some very effective defense against
harmful substances (e.g. xenobiotic transformation against mycotoxins, antioxidant
defense agains hydrogen peroxide )
The animals - mostly herbivorus animals - intake many different plant derived toxins
which are chemically different BUT:
- substrate specificity of xenobiotic transforming enzymes are very wide
- catalytic activity of those enzymes are relatively low
Xenobiotic metabolism have connection with the metabolism of endogenous substrates
Xenobiotic metabolism  Metabolism of endogenous substrates
Xenobiotics  Cytochrom P450
sulphotransferase
Xenobiotics 

steroid metabolism
(e.g. estrone sulphate - faeces)
UDP-glucoronyl - transferase  bilirubin conjugation
WHICH WAS THE FIRST ? OR THEY DEVELOPED TOGETHER ?
Xenobiotic transformation is very important process for the organism because :
- mostly lipophilic xenobiotics excrete from the organism very slowly
- longer exposition time - longer period of toxicity - more toxic processes
- repeated exposition - accumulation in tissues - reach toxic level even at subtoxic level
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MECHANISM OF XENOBIOTIC TRANSFORMATION
1. During the transformation the lipophilic toxicant transferred into water - soluble form
Lipophilic compounds : more effective absorption and resorption , lower rate of excretion
2. Phase I. and Phase II. of xenobiotic transformation can occur separately and Phase II. not necessarily followed the Phase I.
Phase 1. : oxidative bio-transformation
reductive bio-transformation
hydrolytic bio-transformation
Oxidative : smooth endoplasmic reticulum
NADPH + molecular (reactive) oxygen
catalyse by the cytochrome P450 enzyme family
Basic types of reactions:
 aromatic and aliphatic hydroxylation
 N,O,S-desalkylation
 sulphoxidation
 N-oxidation
 epoxidation
Reductive : NADPH-cytochrome c reductase
Cytochrome P450 enzyme family
 convert of azo-, or nitro- compounds to  amino compounds
Hydrolytic : -partly reactions catalyse by hydrolases - breakdown of esters
-partly hydrolytic conversion catalyse by cytochrome P450 monooxygenase in
presence of molecular (reactive) oxygen
Phase 2.: bio-transformation - synthetic conjugation
(metabolic breakdown of xenobiotics are chemically synthesis because in many
cases it produces higher molecular weight compounds )
CONJUGATION : requires electrophil activated donor molecules - except glutathione.
DONORS:
UDP - GLUCOROINIC ACID : glucoronidation
Synthesis of UDP-glucoronic acid :
Glucose-1- P + UTP  UDP-glucose + Pi  +2 NAD  UDP-glucoronic acid + 2NADH
Catalysing enzyme: UDP-glucuronosyl-transferase
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Example for the mechanism of glucoronidation:
Hem catabolism: - FUNTION: excretion of free hem from the organism because the
free hem can initiate oxygen free radical formation
Hem  hem-oxygenase biliverdin  + NADPH  bilirubin + NADP
 + UDP-glucoronic acid  bilirubin - glucuronoid
PAPS ( 3’-PHOSPHO-ADENOSINE-5’-PHOSPHO-SULPHATE) : sulphation
Mechanism of PAPS formation :
ATP + SO4  Adenylyl - sulphate + 2 Pi  + ATP  PAPS + ADP

rate-limiting factor (sulphated polysaccharide (GAGPS) catabolism)
Catalysing enzyme: sulpho-transferase
S-ADENOZYL-METHIONINE : methylation, alkylation
Formation of S-adenozyl methionine :
Methionine + ATP  S-adenozyl-methionine + Pi + PPi
Catalysing enzyme: methyl-transferase
S-ACETIL - COENZYME A : acetylation
GLUTATHIONE (-L-GLUTAMYL-L-CISTEINYLGLYCINE) CONJUGATION
GLUTATHIONE SYNTHESIS: glutathione is a tripeptide but it does not synthesise
during the traditional peptide (protein) synthesis .
i. Glu + Cys   - glutamylcisteine-synthetase  -L-glutamyl -L- cysteine
ii. -L-glutamyl -L- cysteine + Gly  glutathion-synthetase  GSH
Regulation of GSH synthesis: GSH inhibits the -glutamylcysteine - synthetase
Alternative route : Glu + Cys  -glutamyl-cyclotransferase  5-oxoproline
REACTIONS OF GLUTATHIONE :
GSH + GSH  GSSG (glutathione disulfide)
generally used name : oxidised glutathione
But oxidised glutathione would be ( in biological systems ) :
- glutathione sulphoic acid : GSO2H
- glutathione sulphonic acid : GSO3H
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- S-sulphoglutathione :
GSSO3H
GSH + xenobiotic (electrophilic compound )  GSH-transferase  GSH-conjugate
GSH-S-TRANSFERASE INDUCERS:
(according to the chemical form of xenobiotics)
P-450 1A1  1A2 : 3-metylchlorantrene , -naphtoflavon
P-450 2B1  2B2 : phenobarbital, isosafrol
P-450 2E1 :
ethanol, acetone
P-450 3 :
dexamethasone
P-450 4 :
clofibrate (peroxisome proliferating agent )
All of P450 compounds activate by dimethyl-amino-azo-benzene , arochlor (PCB)
EXAMPLE : NEGATIVE EFFECT OF GLUTATHIONE-CONJUGATION :
1,2-Dibrome-ethane (ethylene-dibromide) - insecticide
GSH + EDB  S-(2-haloethyl)-conjugate  half mustard
(1 chlorinated group - mustard gas : 2 )
CHEMICAL MUTAGENEIS
DNA ADDUCT FORMATION: formation of covalent bond(s) between the carcinogenic and/or
mutagenic compound and the DNA molecule
Some of compound form DNA binding (adduct) directly some others only after metabolic
activation.
DNA adduct formation by different compounds:
(1) Polycyclic aromatic hydrocarbons: bound through exocyclic amino groups of A and G
(2) Aromatic amines : bound through C-8 group of G
(3) Nitrosoamines : alkilation of exocyclic oxygen atom at T,C,G
(4) High-energy radiation: - direct radiation energy
- indirect–through the radicals formed from the radiolysis of water
e.g. O2 + e- aq  O2e- + H2O  e- + H2O+ + ee-+ nH2O  e-aq
H2O+ + H2O  OH + H3O+
e-aq + H2O  H + OHThe effects – adduct formation – leave a fingerprint on DNA molecule, which is detectable
Problem I.: amount of DNA is low in the cells
e.g. composition of liver cell : 70 % water, 20 % protein, 5 % lipid, 1 % RNA, 0,2 % DNA
Problem II.: amount of DNA adducts within the DNA also very low and some compound
metabolise
even in the cytosol.
e.g. 6 mg benzo(a) pyrene : it means 25 mol --- DNS adduct :  10 pmol/ mg DNA
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1 g liver contains approximately 2 mg DNA which means approximately 20 pmol/g compound
Practically only about 1 ppm benzo(a)pyrene bound to the DNA
Detection of fingerprints: requires synthetic metabolites as standards
Detection of modified bases – very difficult because of the extremely low amount in biological
systems.
Novel possibility: immunological detection of C-8 adducts
e.g. guanosine-8-yl-acetylaminofluorene; dezoxiguanosine-8-yl-aminofluorene
(both are haptens in a protein complex)
Detection of oxidised metabolites – detection of the effects of oxidative stress
e.g. 8-oxoguanosine or 8 - hydroxyguanosine
Mechanism of oxidation and/or reduction of guanine
Guanine  oxidation  8-hydroxy-deoxyguanine  8-oxo-7,8-dihidro-2’-deoxi-guanine
reduction  imidasole ring opening  2-amino-4-oxi-5-formamido-formamidopyrimidine product formation 6-deoxy-ribosyl- aminopyridine
Oxidised product: 8-oxo-guanosine – stable and detectable – excreted trhough urine
DNA conformation changes as effect of adduct formation:
Guanine O-6 or N-2 adduct – release of hydrogen bonds  opening the double helix
Guanine C-8 adduct – intact DNS conformation – hydrogen bonds remain stable
Mutations: also natural process - evolution
BUT
“undesirable” side effects of mutations (genetic diseases, tumour formation)
(1) “Base exchange” mutation: G : C  T : A
G :C  C : G
G:CA:T
A : T  T: A
A:T C:G
A:T G:C
(2) Insertion : more bases in DNA - triplet mistake – frame-shift in transcription
(3) Deletion : less bases in DNA - triplet mistake – transcription mistake
DNA chain break : DNA desoxyribose + phosphodiester bond break
All the compounds damage the “Integrity” of DNA chain which damage the sugar of phosphor part
Single strand break : detectable only in denaturated DNA
Double strand break : detectable in native DNA
SSB – easy repair
DSB – more difficult to repair
DNS repair mechanisms : stucture of DNA chemically more stable than RNA, more resistant to
hydrolysis
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Direct repair: eg. O6-metilguanin – repair by DNA methyl-transferase
(suicide enzyme – inactivite itself - once onlyreaction)
Base-splicing repair: remove the damaged base by the hydrolysis of glycoside bond between base
and
desoxyribose (e.g. damaged uracil with uracil DNA-N-glucosilase
Nucleotide splicing repair: remove one or more nucleotide unit at the site of damage from the DNA
chain (important in case of UV radiation when abnormal base to base
bond formed on the same chain – e.g. cyclobutylimine dimer formation)
ELIMINATION OF HEAVY METALS
PHASE 1. : expression of metallothionein (metal-binding proteins) genes after heavy metal
exposition ( induced by : Cd, Pb, Hg etc.)
PHASE 2. : excretion / store of metal-protein complex
FACTORS AFFECTING TOXICITY
- duration and frequency of exposition ( chronicity factor)
- empty or full GIT - presence of other materials
- factors affecting feed intake (temperature, light intensity etc.)
- biological factors - species, genotype, sex, age (activity of microsomal xenobiotic transforming
enzyme system)
- chemical factors - solubility (non-polar compound absorption regularly higher)
- optical isomers (cis / trans - different toxicity)
- physical factors - droplet size (e.g. herbicides)
GENERAL PRINCIPLES OF THERAPY
1. Decrease / inhibit further absorption
2. Shock therapy
3. Using specific antidotes (if known) - e.g. EDTA against metals
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SYSTEMATIC TOXICOLOGY
AMINO ACID TOXICOSES
CAUSE: mainly in case of excess amount in feed (higher than requirement)
Toxic symptoms are more harmful : young age (lack of enzyme adaptation)
cool season (more feed intake)
L-isomer (except Met)
PHENYLALANINE TOXICOSIS
SENSITIVE SPECIES: poultry
1 % surplus - retarded growth  7 % surplus - mortality
SYMPTOMS: neural disorders ( niacin deficiency improve disorders)
TYROSINE TOXICOSIS
SENSITIVE SPECIES: poultry and mammals
SYMPTOMS: liver necrosis, kidney failure, cataract ( niacin deficiency improves disorders)
BIOCHEMICAL EFFECT: inhibition of ascorbic acid synthesis
TRYPTOPHAN TOXICOSIS
SENSITIVE SPECIES: poultry and mammals
SYMPTOMS: retarded growth (poultry) , kidney failure (mammals), excitement, convulsions
(serotonin overload of brain)
METHIONINE AND CYSTEINE TOXICOSIS - clinical signs mainly cause by cysteine
PATHOLOGICAL SYMPTOMS: enlargement of kidney (dilated tubuli), necrosis in liver and
pancreas.
SYMPTOMS: neural disorders - Met  Cys transformation requires Ser (decrease brain Ser)
HISTIDINE TOXICOSIS
SYMPTOMS: retarded growth (poultry) , kidney failure (mammals)
(Gly and Arg supply decrease symptoms )
GLYCINE TOXICOSIS - non - essential amino acid toxicosis
SENSITIVE SPECIES: poultry
SYMPTOMS: retarded growth ( niacin deficiency improve disorders)
CAUSE OF TOXICITY: extreme ammonia, oxalate and glycolic-acid production
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THERAPY : addition of folic acid, vitamin B12, Met
VITAMIN TOXICOSES
CAUSE: mainly in case of excess amount in feed (higher than requirement)
VITAMIN
TOXIC EFFECTS
GENERAL SAFE LEVEL
A
depressed growth , reduced bone
4-10 x requirement
ash, embryo toxicity
D
weight loss, renal tubular
4-10 x requirement
calcification, blood vessel
calcification
E
weight loss, reduced plasma Ca, P
100-200 x requirement
level, altered prostanoid synthesis
K
no real problem
1000 x requirement
C
no real problem (possibly increase
1000 x requirement
severity of iron toxicosis)
Thiamine
no real problem
1000 x requirement
Niacin
depressed growth, decrease milk
2000 x requirement
production (dairy cow)
(5 g/day dairy cow)
Riboflavin
no real problem
1000 x requirement
Pyridoxine
ataxia, muscle weakness
1000 x requirement
(only in mammals)
Folic acid
no real problem
1000 x requirement
Pantothenic acid
no real problem
1000 x requirement
Biotin
no real problem
10 x requirement
B12
no real problem
10 x requirement
Choline
reduced body weight and feed
10 x requirement
efficiency
(2-5 x in poultry !)
fishy taint in eggs (poultry)
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METAL TOXICITY
ALUMINIUM - route of toxicity mainly feed (contamination of zinc)
SENSITIVE SPECIES: poultry, sheep
CAUSE OF TOXICITY: secondary phosphorus deficiency (Al-P complex)
SYMPTOMS: retarded growth, muscle weakness, neural disorders
PATHOLOGICAL SIGNS : liver necrosis, lipofuscin accumulation in substantia nigra
ANTIMONY ( Sb+3 more toxic than Sb+5 ) - route of toxicity mainly inhalation
SENSITIVE SPECIES: all farm animal
SYMPTOMS: interstitial pneumonia
PATHOLOGICAL SIGNS : fatty liver degenerative necrosis
ARSENIC ( As+3 more toxic than As+5 , organic form more toxic than inorganic ) - route of toxicity
mainly with feed
SENSITIVE SPECIES: all farm animal
CAUSE OF TOXICITY: inhibition of -SH groups, specific inhibition of lipoate dependent enzymes
(pyruvate dehydrogenase complex)
SYMPTOMS: vomiting, diarrhoea, convulsions, dehydratio
BARIUM - route of toxicity mainly with water
SENSITIVE SPECIES: all farm animal
CAUSE OF TOXICITY: extreme muscle contraction activation
SYMPTOMS: GIT - vomiting, diarrhoea
cardiovascular system - hypertension, heart break in systole
skeletal muscle - convulsions
BISMUTH (inorganic - low absorption, organic - through skin) - route of toxicity mainly with feed
SENSITIVE SPECIES: all farm animal
CAUSE OF TOXICITY: encephalopathia, inclusion in proximal tubuli of kidney
SYMPTOMS: convulsions, lethargy, kidney failure
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BORON (absorption from GIT also from lung) - route of toxicity through water and
inhalation ( BH3 or B2H6 )
SENSITIVE SPECIES: all farm animal
SYMPTOMS: reproductive problems in both sex
BROMIUM - route of toxicity mainly with water (no real practical problem)
SENSITIVE SPECIES: all farm animal
SYMPTOMS: impaired movement, kidney failure
BARIUM - route of toxicity mainly with water
SENSITIVE SPECIES: all farm animal
CAUSE OF TOXICITY: extreme muscle contraction activation
SYMPTOMS: GIT - vomiting, diarrhoea
cardiovascular system - hypertension, heart break in systole
skeletal muscle - convulsions
CADMIUM - route of toxicity mainly with water and feed (contamination of Zn)
(absorption rate is very low 2-3 %, but retention is high)
SENSITIVE SPECIES: all farm animal
CAUSE OF TOXICITY: secondary iron and magnesium deficiency
SYMPTOMS: kidney failure, testicular atrophy, decrease hydrogen-peroxide production of
macrophages (pre-carcinogenic)
CHROMIUM (Cr2+ more toxic except Cr2O3) - route of toxicity mainly with water
SENSITIVE SPECIES: all farm animal (decrease toxicity of V in chicken)
CAUSE OF TOXICITY: protein precipitation and oxidation
SYMPTOMS: dermatitis - direct skin contact
ulcerogenic- stomach + inflammation in GIT
COBALT - route of toxicity mainly with feed (no real problem)
SENSITIVE SPECIES: all farm animal
CAUSE OF TOXICITY: secondary iron deficiency
SYMPTOMS: depressed growth rate, anaemia
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COPPER - route of toxicity mainly with feed
SENSITIVE SPECIES: acute toxicity (sheep and turkey), chronic toxicity (all)
CAUSE OF TOXICITY: copper accumulation in liver + haemolytic crisis
inhibition of -SH groups (e.g. GSH-copper complex)
SYMPTOMS: reduced growth rate, weight loss, low appetite (before crisis)
icterus, haemolysis (high mortality)
PATHOLOGICAL SIGNS : lipofuscin granules in tubular epithelium and in parenchymal tissue of
liver (lysosomal reaction)
FLUORINE - route of toxicity mainly with water also with rock phosphates
SENSITIVE SPECIES: all farm animals
CAUSE OF TOXICITY: accumulation in bones (and teeth)
SYMPTOMS: chronic : spots on teeth, osteofluorotic bone lesions (first at metatarsus)
acute: anorexia, vomiting, depression - lethal within one day
(sodium -fluorosilicate (rodenticid), NaF (antihelminthicum) toxicosis)
IODINE - route of toxicity mainly with feed (contamination with soil)
SENSITIVE SPECIES: all farm animals
CAUSE OF TOXICITY: accumulation in thyroids - inhibition of iodine uptake by thyroids
SYMPTOMS: antithyroid, goitrogenic , embryotoxic (rodents), weight loss (cattle)
IRON - route of toxicity mainly with feed ( iron supplementation)
( Fe2+ more toxic, per os application less toxic than i.m.)
SENSITIVE SPECIES: acute toxicity (piglets), chronic toxicity (young animals)
CAUSE OF TOXICITY: iron accumulation (free iron in blood circulation),
secondary copper, phosphorus and selenium deficiency
SYMPTOMS: reduced growth rate, weight loss, lower feed intake, diarrhoea
acute toxicosis in piglets: anorexia, oliguria, diarrhoea, hypothermia, shock
PATHOLOGICAL SIGNS : oedema
LEAD - route of toxicity mainly with feed ( + inhalation and through skin)
absorption from GIT is low : 10 % (  3 % ruminants) BUT young animals 50-90 % !
(vitamin D improve absorption)
SENSITIVE SPECIES: all farm animals (mainly grazing animals)
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CAUSE OF TOXICITY: lead accumulation in liver and kidney (muscle, milk)
inhibition of porphyrin and hem, impaired protein synthesis,
increase RBC fragility, impaired endocrine functions
SYMPTOMS: hypochrom anaemia, anorexia, reduced growth rate, weight loss, low appetite,
diarrhoea, vomiting, salivation, blindness (cattle), abortion, excitement (calves)
PATHOLOGICAL SIGNS : protein bound lead-, calcium- and phosphorus granules in kidney
tubuli
MAGNESIUM - route of toxicity mainly with feed ( limestone of dolomite origin and green grass)
SENSITIVE SPECIES: all farm animals
CAUSE OF TOXICITY: magnesium overload - Ca/Mg imbalance (inhibition of parathormone
synthesis)
SYMPTOMS: moderate toxicosis : diarrhoea (severity depend on the amount of intake),
decrease egg shell thickness
severe toxicosis: impaired reflex functions (heart, breath)
MANGANESE - route of toxicity mainly with feed ( and dust)
iron decrease toxicity
SENSITIVE SPECIES: all farm animals
CAUSE OF TOXICITY: secondary iron deficiency
SYMPTOMS: reduced growth rate, reproduction problems (females only)
PATHOLOGICAL SIGNS : low haemoglobin content of blood,
necrosis of basal ganglions (in case of inhalation only)
MERCURY - route of toxicity mainly with feed
alkyl-Hg higher rate of absorption than others, methyl-Hg 100 %
absorption (selenite reduce mercury toxicity)
SENSITIVE SPECIES: all farm animals
CAUSE OF TOXICITY: mercury accumulation in kidney and liver (t1/2 : 70 d in poultry),
alkyl-Hg can pass through the blood-brain barrier
SYMPTOMS: acute toxicosis: shock, arrhythmia, vomiting
chronic toxicosis: reduced growth rate, weight loss, forced breath, salivation,
teeth loss (horse)
PATHOLOGICAL SIGNS : glomerulonephritis, colon necrosis
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MOLYBDENUM - route of toxicity mainly with feed (absorption depends on the actual sulphur
supply)
SENSITIVE SPECIES: all farm animals
CAUSE OF TOXICITY: secondary copper deficiency
SYMPTOMS: diarrhoea, anorexia, anaemia (coeruloplasmin deficiency), haemoglobinuria,
reduced libido, testicular atrophy, paralysis (deficiency of dopamin--hydroxylase), retarded growth (deficiency of cytochrome-c-oxidase)
NICKEL - route of toxicity mainly with feed and water (absorption : 10 % )
SENSITIVE SPECIES: all farm animals
CAUSE OF TOXICITY: nickel accumulation in tissues, secondary Zn deficiency
SYMPTOMS: low appetite, moderate anaemia, polyuria, low hatchability (poultry), dermatitis,
parakeratosis
PATHOLOGICAL SIGNS : lesions in lung
PHOSPHORUS - route of toxicity mainly with feed supplements
SENSITIVE SPECIES: all farm animals
CAUSE OF TOXICITY: calcium/phosphorus imbalance
SYMPTOMS: urolithiasis (in kidney of ruminants), impaired movement
PATHOLOGICAL SIGNS : osteodistrophia fibrosa - fibrous tissue in bones instead of mineralised
structure
POTASSIUM - route of toxicity mainly with feed ( no real problem in practice)
SENSITIVE SPECIES: all farm animals (mainly ruminants)
CAUSE OF TOXICITY: excess potassium inhibit the absorption of magnesium
SYMPTOMS: tetany (hypomagnesaemia)
SELENIUM - route of toxicity mainly with feed additives and some selenium accumulating plant
(e.g. Astragallus ssp. ) ; organic selenium absorption is higher, but less toxic
SELENIUM COMPOUNDS IN FEEDS:
- hydrogen-selenide - very toxic gas
- organic selenides - volatile compounds
- heavy metal selenides - insoluble compounds
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- selenium - insoluble
- selenite - soluble and potentially toxic ( transform into elemental selenium in acidic
environment- e.g. acidosis in rumen)
- selenates - soluble and potentially toxic
SENSITIVE SPECIES: all farm animals
CAUSE OF TOXICITY: selenium accumulation in tissues
SYMPTOMS: acute toxicosis: distress effect - forced breath, ataxia, diarrhoea, vomiting,
impaired movement
chronic toxicosis: impaired movement, hair loss, reproduction problems,
abnormal hoof development, weight loss
PATHOLOGICAL SIGNS : liver and kidney necrosis, haemorrhages in myocardium
SILICA - route of toxicity mainly with feed (dust) ( no real problem)
SENSITIVE SPECIES: all farm animals (mainly ruminants and horse)
CAUSE OF TOXICITY: extreme silica intake
SYMPTOMS: urolithiasis (in kidney of ruminants), low feed intake, impaired reproduction
SILVER - route of toxicity mainly with feed (quick excretion)
SENSITIVE SPECIES: all farm animals (mainly poultry)
CAUSE OF TOXICITY: secondary selenium deficiency
SYMPTOMS: heart enlargement, muscle dystrophy in gizzard, exudative diathesis
SODIUM CHLORIDE - route of toxicity mainly with feed supplements
SENSITIVE SPECIES: all farm animals
CAUSE OF TOXICITY: ion imbalance
SYMPTOMS: ruminants: anorexia, low water intake, weight loss, diarrhoea, vomiting
poultry: increase mortality, retarded growth, convulsions
PATHOLOGICAL SIGNS : kidney necrosis
STRONTIUM - route of toxicity mainly with feed supplements
SENSITIVE SPECIES: all farm animals
CAUSE OF TOXICITY: replacement of calcium in physiological processes (lower activity)
SYMPTOMS: rachitis - strontium form insoluble complex with phosphorus
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SULPHUR - route of toxicity mainly with feed supplements (inhalation)
(both organic and inorganic form absorption is high)
SULPHUR IN FEEDS
elemental sulphur - non toxic
H2S - very toxic
sulphur - dioxide - non toxic
organic sulphur - Met and Cys can be toxic
SENSITIVE SPECIES: all farm animals
CAUSE OF TOXICITY: impaired metabolism of sulphur (e.g. vitamin A deficiency impair
sulphotransferase activity - not bound to mucopolisacharides)
SYMPTOMS: general symptoms: anorexia, retarded growth, diarrhoea, depression
in case of inhalation: lung fibrosis + mortality
PATHOLOGICAL SIGNS : lung emphysema, liver necrosis
TIN - route of toxicity mainly with feed (absorption rate is very low)
Toxic symptoms depend on the tin compounds (organic compounds are more toxic : e.g. alkyl-Sn)
SENSITIVE SPECIES: all farm animals
CAUSE OF TOXICITY: induction of hem-oxygenase (increase hem metabolism in kidney and
inhibit hem-dependent cellular functions)
SYMPTOMS: retarded growth, reproduction problems, neural disorders
PATHOLOGICAL SIGNS : pancreas atrophy, testicular degeneration, calcification in kidney,
brain damage (status spongiosus)
TUNGSTEN - route of toxicity mainly with water
SENSITIVE SPECIES: all farm animals
CAUSE OF TOXICITY: inhibit xanthine oxidase activity in liver
SYMPTOMS: diarrhoea, coma
URANIUM (non radioactive) - route of toxicity mainly with feed and water
SENSITIVE SPECIES: all farm animals
CAUSE OF TOXICITY: uranium form complex with proteins of the columnal cells of kidney
tubuli
SYMPTOMS: uraemia
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VANADIUM - route of toxicity mainly with feed supplements (rock phosphates)
Absorption rate is very low : 0.5 - 1 % !
( chromium decrease, selenium increase severity of toxicity)
SENSITIVE SPECIES: all farm animals
CAUSE OF TOXICITY: inhibition of Na/K-ATP-ase, activation of adenylate cyclase in heart
SYMPTOMS: only acute toxicosis : diarrhoea, desiccation, impaired movement
PATHOLOGICAL SIGNS : haemorrhages in heart, liver, kidney, intestine
ZINC - route of toxicity mainly with feed supplements
( high - non toxic - zinc potentiate the effect of some pesticides - e.g. DDT)
SENSITIVE SPECIES: all farm animals
CAUSE OF TOXICITY: secondary calcium, copper, iron deficiency
SYMPTOMS: weight loss , anaemia, lowers bone ash content, embryo toxicity
(selenium deficiency improve the severity of symptoms)
NITRATE - NITRITE TOXICITY
General principles: nitrate less toxic than nitrite but during the digestion / rumen fermentation very
toxic compounds will be form - hydroxylamine, ammonia, nitrosoamines etc.
Nitrite: absorption is very quick – Hb  MetHb + vasodilatation
Causes of toxicity: - high nitrite containing feed
- excess dose of antihelminthic drug ( dog )
- nitrate accumulating plants (in ruminants)
Symptoms: ( clinical symptoms can be found only after approximately 50 % transformation of Hb)
- quick and weak pulse, subnormal body temperature, muscle weakness, ataxia,
cyanosis
19
Maximum tolerable level of metals in farm animals (NAS, 1986)
(predicted values in brackets)
METAL
Aluminium
Antimony
Arsenic (inorg.)
Arsenic (org.)
Barium
Bismuth
Boron
Bromium
Cadmium
Calcium (%)
Chromium
Cobalt
Copper
Fluoride
Iodine
Iron
Led
Magnesium ( %)
Manganese
Mercury
Molibdenum
Nickel
Phosphorus( %)
Potassium (%)
Selenium
Silica ( %)
Silver
NaCl ( % )
Strontium
Sulphur ( %)
Tin
Titan
Wolfram
Uranium
Vanadium
Zinc
CATTLE
1000
50
100
(20)
(400)
150
200
0,5
2
(1000)
10
100
40-100
50
1000
30
0,5
1000
2
10
50
1
3
(2)
(0,2)
4-9
2000
(0,4)
(20)
50
500
SHEEP
1000
50
100
(20)
(400)
(150)
(200)
0,5
2
(1000)
10
25
60-150
50
500
30
0,5
1000
2
10
(50)
0,6
3
(2)
0,2
9
(2000)
(0,4)
(20)
50
300
PIG
(200)
50
100
(20)
(400)
(150)
200
0,5
1
(1000)
10
250
150
400
3000
30
(0,3)
400
2
20
(100)
1,5
(2)
2
(100)
8
3000
(20)
(10)
1000
POULTRY
200
50
100
(20)
(400)
(150)
2500
0,5
1,2 - 4
1000
10
300
150-200
300
1000
30
(0,3)
2000
2
100
(300)
0,8 -1
(2)
2
100
2
10000
20
10
1000
HORSE
(200)
(50)
(100)
(20)
(400)
(150)
(200)
(0,5)
2
(1000)
(10)
800
(40)
5
(500)
30
(0,3)
(400)
(2)
(5)
(50)
1
(3)
(2)
(3)
(2000)
(20)
(10)
(500)
RABBIT
(200)
70-150
50
(100)
(20)
2000
(150)
(200)
(0,5)
2
(1000)
(10)
200
(40)
(500)
(30)
(0,3)
(400)
(2)
500
(50)
1
(3)
(2)
(3)
(2000)
(20)
(10)
(500)
20
OTHER TOXIC COMPOUNDS AND ANTINUTRIENTS IN FEEDSTUFFS
GLUCOSIDES:
CYANOGENIC GLUCOSIDES
Occured in: linseed, cassava (linamarin), javabean (phaseolunasin) sudan grass and sorghum
(durrin)
Cause of toxicity: HCN release from glycoside (HCN inhibit cytochrome oxidase ) - cyanosis
GLUCOSINOLATES
Occured in: Brassica sp., rapeseed
Cause of toxicity: glucosinolates are not toxic but myrosinase enzymes hydrolyse them to toxic
metabolites (thyocyanate, isothyocyanate, nitriles, goitrin) in GIT
Toxic effects: reduced uptake of iodine by the thyroid gland
Symptoms: growth depression, thyroid and kidney enlargement, abortion
ALKALOIDS:
SOLANINE - glycoalkaloid (alkaloid + glucoside)
Occurred in: potato
Toxic effects: severe gstrointestinal disturbances and neurological disorders
Symptoms: acute hemorrhagic gastroenteritis, salivation, forced breath, progressive paralysis
LUPIN ALKALOIDS : LUPANIN, LUPININ, LUPANIDIN, SPARTEIN
Occurred in: sweet lupin
Symptoms: anorexia, forced breath, teratogenic ( cattle)
LATHYRISM (dual problem but same name)
Lathyrism of cattle and horses : chronic, progressive neurological disorder
Symptoms: paralysis of back side of body (mainly after sorghum intake)
polyuria, haemoglobinuria
Lathyrism followed by Lathyrus seed intake: beta-amino-proprionitrile toxicosis (alkaloid)
Symptoms: paralysis of larynx (horse) , aorta rupture (turkey pullets)
21
ANTINUTRIENTS
Groups of antinutrients :
1. Group of those factors which are inhibit digestion and /or utilisation of proteins:
( trypsin-, chymotripsin inhibitors, lectins, polyphenol compounds, saponins)
2. Group of those factors which are inhibit digestion of carbohydrates:
(amylase inhibitors, polyphenolic compounds)
3. Group of those factors which are inhibit utilisation of minerals:
(glycosynolates, oxalic acid, phytic acid, gossypol)
4. Anti-vitamins - inactivate vitamins and increase requirement
PROTEASE INHIBITORS
Colostral milk trypsin inhibitor: serine-protease inhibitor which improve the development of
colostral immunity
Soya trypsin inhibitors: serine protease inhibitors which are inhibit beside trypsin chymotrypsin, as
well (trypsin inhibitors have important functions in plants : e.g. defence against proteolysis and/or
autolysis)
Kunitz inhibitors : active centre Arg
Bowmann-Birk inhibitors: active centre Lys-Ser (trypsin inhibition)
Leu-Ser (chymotrypsin inhibition)
Aspartate protease inhibitors: active centre Asp
Metallo-protease inhibitors: inhibition of carboxy-peptidases
NUTRITIVE EFFECTS OF PROTEASE INHIBITORS:
- GROWTH RETARDATION
- ENLARGEMENT OF PANCREAS (negative feed back mechanism)
LECTINS OR PHYTOHEMAGGLUTINS
LECTINS are proteins that bind reversibly with sugars and glycoconjugates on the surface of the
microvilli lining in the small intestine:
cause impairment of the absorption if nutrients (e.g. glucose, amino acids etc.) across the
intestinal wall for that reason they are reach the colon where fermented
LECTINS IN FEED : soya lectin - soyin
bean lectin - phasin
22
SAPONINS
Chemical structure of saponins: steroid or triterpene groups attached to sugar moieties
Effects of saponin: - inhibit digestive and metabolic enzymes
- form insoluble complexes with zinc
- foam formation during ruminal fermentation (also inhibit rumen wall receptors)
Occurrence in feed: alfalfa - limiting factor of alfalfa meal inclusion in monogastric diets
POLYPHENOL-TYPE COMPOUNDS
Positive effect of polyphenols : reduce severity of diarrhoea (e.g. tannins)
Negative effects of polyphenols: decrease (inhibit) digestion of proteins (e.g. bypass proteins in
ruminants)
Phenolic compounds + polyphenol oxidase  kinons + amino acids, peptides  irreversible
complex
Form insoluble (not absorbable) complex with some metals (e.g. iron)
Symptoms of tannin intake: - reduced growth
- anaemia
Occurrence in feeds: rapeseed, faba beans, sorghums
PHOTOSENSITING COMPOUNDS
Photosensibilisation: poorly pigmented skin show hyperactive reaction against sunshine because of
presence of some photosensitising compound in skin.
Those compounds bound the energy of sunshine and given it to other molecules - e.g. initiate
oxygen free radical formation
Possible cause of photosensibilisation:
- direct contact ( e.g. plant psoralenes)
- ingestion (e.g. chlorophyll accumulation in skin)
- endogenous route (e.g. aberrant metabolism of haemoglobin )
Occurrence in feedstuffs:
Primary compounds: hypericin (Hypericum sp.)
furocoumarin (Umbelliferae, Rutaceae)
Secondary or hepatogenous compounds : unknown compound in alfalfa
Photosensibilising mycotoxins : psoralenes (Sclerotinia sp.)
sporidesmin (Pithomyces sp.)
23
ANTIVITAMINS
Competitive antagonist compounds :
COUMARIN or dicoumarol : antagonist of vitamin K
Cause of toxicity: inhibition of Ca-binding side chain formation of prothrombin
Symptoms: bleeding (capillary rupture), delayed clotting
SULPHONAMIDE: inhibition of para-amino-bensoic acid (PABA)
Symptoms: vitamin deficiency ( inhibition of bacterial vitamin synthesis)
Vitamin decomposition compounds:
THIAMINASE : decomposition of thiamine
Toxic symptoms: loss of appetite, high fever, forced breath
Occurrence in feedstuffs: raw seafish meat
LIPOXYGENASE: oxidation of PUFA and PUFA-esters (e.g. linoleic, linolenic, arachidonic acid)
also vitamins A and E
Toxic symptoms: retarded growth, reproduction/fertility problems, deficiency of vitamins A and E
Occurrence in feedstuffs: soya, alfalfa, bean, sweet lupin
PHYTOESTROGENS
Oestrogen-like compounds in plants : isoflavons, coumestans, resorcyclic acid lactons
Toxic effects: irreversible binding to oestrogen receptors
Toxic symptoms: low fertility, acyclia, metritis, abortion, early puberty
Occurrence in feed stuffs: mainly in grass species - red clover, red fescue etc.
24
TOXICOSES CAUSED BY CHEMOTERAPEUTICS
Chemoterapeutics are antimicrobial compounds which are use regularly in very low dose as growth
promoter in feed (up to 01.01.2006)
FURAZOLIDONE toxicosis (nitrofurane group ) – banned
Nitrofuranes : nitrofurantoin, nitrofurasone, furazolidone
- mainly ruminant feed contains nitrofuranes - problems with milk replacers
Symptoms: acute toxicosis - clinical symptoms develop very quickly - mortality within 12-24
hours
- quick decrease of appetite, convulsions, salivation,
- high pulse rate, extremely high breath rate,
- calves unable to weak up again
chronic toxicosis - symptoms develop shorter or longer period of time according to dose
- damage of bone marrow - severe anaemia, marked reduction of thrombocyte and WCB
- clinical symptoms: diarrhoea, depression, exciting, convulsions
Pathological symptoms: necrosis in spleen, liver, kidney, inflammation in small intestine,
haemorrhage in organs (muscle)
COCCIDIOSTAT toxicoses
Monensin toxicity ionophore (polyether - type) antibiotic.
Metabolic product of Streptomyces cinnamonensis.
Incompatibility with tiamulin.
Toxicosis in relatively few cases - e.g. Poultry : > 120 ppm
Symptoms: retarded growth (broiler chicken), egg production decrease (layers)
paralysis of legs (turkey)
Pathological symptoms: liver damage (mitochondrial swelling).
Salinomycin toxicity
Toxicity : > 100 - 120 ppm Incompatibility with tiamulin
Cattle : optimal 40 ppm, toxicosis over 200 ppm
Symptoms: low feed intake (mainly concentrate), severe diarrhoea, ataxia, high pulse rate, forced
breath, uncoordinated movement
Pathological symptoms: damage of heart- and skeletal muscle ( similar as vitamin E / Se
deficiency)
25
HERBICIDE AND PESTICIDE TOXICITY
INSECTICIDES
NICOTINE-SULPHATE - banned
Symptoms: diarrhoea, vomiting, convulsions, paralysis, forced breath
Pathological symptoms: haemorrhages in heart and lung
PIRETRINES and PIRETROIDS
Piretrines: natural compounds isolated from Chrysantemum cinerariaetolicum
Piretroids: synthetic derivatives of natural piretrines (allethrin, cypermethrin, decamethrin,
fenvalerate, flevanilate, pamethrin, atrametrin).
Symptoms: allergy reactions (direct skin contact), paralysis (high dose)
Note: carrier materials can be also very toxic sometimes more than piretroid (e.g. petroleum
products (crude oil, xylene etc.)
Toxic effect of carriers: direct effect - skin irritation
indirect effect - aspiration pneumonia.
Symptoms: quick extremely high increase of body temperature
anterior - ventral lesions in lung, pleura exudatio.
ORGANIC PHOSPHATE ESTER TOXICOSIS
CAUSE OF TOXICOSIS: contamination of feed ( period of decomposition 1 to 90 days). Drying
increase stability .
Groups of organic phosphorus esters : orthophosphate - esters (very toxic compounds)
thiophosphate - esters (moderately toxic compounds)
pirophosphate -esters (weak toxic compounds )
Toxicity depends on :
- length of side chain - longer more toxic
- presence of selenium in side chain improve toxicity
- more severe symptoms in young animals ( lack of enzyme adaptation),
- weak body condition - more severe symptoms
- rumen acidosis improve severity of symptoms (more stable at low pH)
Biochemical effects: phosphorilation of acetylcholine esterase enzyme and degradation of its active
side chain.  irreversible inhibition of enzyme activity.
Enzyme inhibition : specific acetylcholine esterases ( CNS, muscles)
unspecific cholin-esterases (blood plasma, liver )
26
Symptoms of acute toxicity: (effects on parasympathetic nervous system)
- Muscarine-like effect - glandular secretion (salivation) + smooth muscle (diarrhoea) - 10-30 min.
- Nicotine-like effect - convulsions, impaired movement - within 1-6 hours
- Central (CNS) effect - excitement and later ataxia - between 6-12 hours
Symptoms of chronic toxicity: inflammation in intestine
neurotoxic effect - (within 1-2 weeks)
paralysis of back side
CARBAMATE TOXICOSIS (cabaryl, dioxicarb, carbofurane)
Less toxic than organic phosphate-esters - period of decomposition much shorter (within hours)
Note: carbamates inhibit substrate specific -acetylcholine esterase - enzyme only
Toxic effects: same as organic phosphorus ester toxicosis
Symptoms: develop very quickly (within 10-15 minutes) , mortality within 1-2 hours
CHLORINATED HYDROCARBON TOXICITY
NOTE: several compounds of this group out of use because of their hepato-carcinogenic side effect
( e.g. DDT, Aldrine, Dieldrin, HCH )
Physiological effects: general excitement compounds of CNS
Symptoms of toxicity (acute): neuromuscular effects - convulsions, salivation, polyuria, depression
Chronic toxicity: chronic encephalitis, hepatotoxic effects
Toxicity depend on :
- age - more severe in young animals,
- hypocalcaemia (calve) improve severity of symptoms
BIPYRIDYL-DERIVATIVE TOXICOSIS (diquat, paraquat)
PARAQUAT
-decomposition very quick on pasture (sunshine) - asympthomatic in cattle, sometimes lesions in
mouth cavity (horse)
Symptoms of toxicosis: - acute: diarrhoea, forced breath, pulmonary edema, uncoordinated
movement
- inhalation: progressive inflammation of bronchus and lung
- per os : lesions in GIT
Note: vitamin E / selenium deficiency improve severity of symptoms
Pathological symptoms: lung fibrosis, kidney- and liver necrosis
27
DIQUAT:
symptoms develop very slowly (sometimes 1-4 weeks after exposition)
Symptoms of toxicosis: - acute: symptoms develop within one day : uncoordinated movement,
excitement, diarrhoea, lung oedema, lesions in mouth cavity and
oesophagus (kidney failure)
Pathological symptoms: liver dystrophy, nephrosis, lung oedema
DINITROPHENOL-TYPE COMPOUND TOXICOSIS (DNOC, Dinobuton, DNBP, Dinocap,
Dinoseb-acetate)
Biochemical effects: uncoupling of oxidation and phosphorylation (ATP production during
carbohydrate metabolism. Extreme heat production from oxidation.
Symptoms of toxicosis: -acute: hyperthermic body temperature > 40-41 oC
cyanosis ( hypoxia (anoxia) - because of hyperventilation)
rigor mortis develop very quickly (ATP deficiency)
- subchronic: weight loss, uraemia, haemoglobinuria, icterus, cataracta
PHENOXY-ACID DERIVATIVES TOXICOSIS (atrazin, simazin)
Symptoms of toxicosis (acute): convulsions, hyperventillation, ataxia, thirst
chronic: progressive paralysis of back side of the body
(progressive degeneration of vertebral neurons)
RODENTICIDE TOXICOSIS
ANTICOAGULANTS - COUMARIN DERIVATIVES
- antagonists of vitamin K (inhibition of I,II,VII,IX,X blood clotting factors)
- both single high and repeated small doses can be lethal
- biological half-life of anticoagulants : 15 hours - 30 days !
Symptoms of toxicosis: bleeding, haemorrhages
ZINC-PHOSPHIDE
Cause of toxicity: phosphoric acid release at low pH ( gastric juice)
Symptoms of toxicosis: vomiting, forced breath, schock, metabolic acidosis, tetany, coma,
insufficient blood circulation
28
MYCOTOXICOSES
CAUSED BY MYCOTOXINS PRODUCE BY MICROSCOPIC FUNGI OR MOULDS
Connection between moulds and feed :
- passive contamination – moulds without active metabolism
- active contamination – moulds with active metabolism
(also causes decrease of the nutritive value of feed )
Factors affecting the reproduction of moulds
- temperature
- moisture content of substrate ( feed)
- RELATIVE HUMIDITY (RH)
Ws
RH % = ------------------------ x 100
Wst
where: Ws : water content of substrate
Wst: critical water content of substrate for saturation
GROUND MOULDS
OPTIMAL HUMIDITY : 20 - 30 %
SPECIES: Alternaria és Fusarium spp..
STORE MOULDS
OPTIMAL HUMIDITY: 14-20 %
SPECIES: Aspergillus és Penicillium Mucor SPP.
Groups of moulds in feeding stuffs
Criteria of groups:
- optimal humidity
HIGH : Higrophyl MEDIUM: Mesophyl , LOW: Xerophyl
- reproduction capacity during storage:
LOW: ephemer
MEDIUM: mezobiontic
HIGH : persistent
29
PLACE OF DAMAGE
PERSISTENCY
OPTIMAL HUMIDITY
(Christensen)
DURING STORAGE
(Pelhate)
(Pelhate)
GROUND MOULDS
EPHEMER
HIGROPHYL
Alternaria
Fusarium
Cladosporium
Trichoderma
Stachybotrys
STORE MOULDS
Aspergillus
Penicillium
Mucorales
Alternaria
Fusarium
Fusarium
Mucorales
MESOBIONTIC
Cladosporium
MESOPHYL
Cladosporium
Alternaria
Aspergillus
Penicillium
XEROPHIL SPECIES
Aspergillus glaucus
Aspergillus restrictus
Aspergillus versicolor
PERSISTENT SPECIES
Aspergillus
Penicillium
Mucorales
PRIMARY AND SECONDARY METABOLISM OF MOULDS
Primary metabolism :
- basic anabolic and catabolic processes
Secondary metabolism :
-
Produce such - among them toxic – compounds (e.g. antibiotics, alkaloids, toxins )
which are not require for the normal metabolic processes of the moulds
- Main site - triketo-acetic acid cycle – polyketide dericvatives
- importance of secondary metabolism products :
1. PHYTOPATHOGEN MOULDS - TOXIC COMPOUNDS
2. STRESS RELATED COMPOUNDS
TOXIN PRODUCTION OF MOULDS
- one species produce different toxins
- one toxin produce by different moulds
- presence of moulds does not mean the presence of toxin
- lack of moulds does not mean toxin free status
- within one mould species some varieties produce toxin while some others not
(TOXINOGENIC AND NON-TOXICOGENIC VARIETIES)
EFFECT OF MYCOTOXINS ON ANIMAL PRODUCTION
30
- Effect of mould (mycelium – cell wall components – allergenic) vs. effect of toxin
- Mould contaminated feed – lower nutrient content (mainly fat – lipase activity of moulds)
- Mostly non specific symptoms
- Low toxin contamination – lower resistance to diseases (impaired immune response)
- lower productivity (feed refusal)
METABOLISM OF TOXINS
Absorption  metabolism – oxidation, reduction, decomposition, synthesis (formation of more
soluble compounds )
 excretion:
through liver –bile juice
through kidney – urine
through ovary - egg
DETECTION TO MYCOTOXINS
-
-
only several mycotoxins can be detected during routine analyses (AFB1, DON,DAS,
OTA, T-2, fumonisins, zearalenone)
metabolism of mycotoxins “cover” the toxin – e.g. zearalenone metabolised by the
microbes to zearalenone-glycoside, which is not detectable as zearalenone in feed but
hydrolyse in the gastro-intestinal tract.
there are no safe level of mycotoxins
effects of metabolites not detectable (e.g. synergistic effects)
31
GROUP OF MYCOTOXINS ACCORDING TO MAIN EFFECTS
MAIN EFFECT
MYCOTOXIN
HEPATOTOXIC
AFLATOXINS
HEPATOCARCINOGENIC STERIGMATOCYSTIN
TERATOGENIC
NEUROTOXIC
AFLATOXIN B1
OCHRATOXIN A
PATULIN
RUBRATOXIN B
CITREOVIRIDIN
PATULIN
NEPHROTOXIC
FUMONISIN
OCHRATOXIN A
DERMATOTOXIC
CITRININ
TRICHOTHECENES
EMETIC
GENITOTOXIC
TREMOROGENIC
PHOTOSENSIBILISING
HALLUCINOGENIC
VOMITOXIN (DON)
TRICHOTHECENES
ZEARALENON
PENTIREM A
FUMITREMOROGENS
PSORALENES
SPORIDESMIN
ERGOT ALKALOIDS
LISERGIC AMINES
MOULD SPECIES
ASPERGILLUS FLAVUS
ASPERGILLUS PARASITICUS
ASPERGILLUS VERSICOLOR
ASPERGILLUS FLAVUS
ASPERGILLUS PARASITICUS
ASPERGILLUS OCHRACEUS
PENICILLIUM SP
PENICILLIUM CITROVIRIDAE
ASPERGILLUS SP.
PENICILLIUM SP.
FUSARIUM MONILIFORMAE
ASPERGILLUS OCHRACEUS
PENICILLIUM SP.
PENICILLIUM CITRINUM
FUSARIUM SP.
STACHYBOTRYS SP.
MYROTHECIUM SP.
FUSARIUM SP.
FUSARIUM SP.
PENICILLIUM CYCLOPIUM
ASPERGILLUS FUMIGATUS
SCLEROTINIA SCLEROTIORUM
PITHOMYCES CHARTARUM
CLAVICEPS SP.
32
AFLATOXINS - Aspergillus flavus, Aspergillus parasiticus
SOURCE: ground nut, cotton seed, oil seeds, soybean, corn
OPTIMAL TEMPERATURE FOR TOXIN PRODUCTION:
AFLATOXIN B1 - 25-30 oC
AFLATOXIN G1- 15-20 oC
AFLATOXIN M1 – in cow’s milk
AFLATOXIN M2 – in ewe’s milk
Chemically : dihydrofurano-furanes : B1, G1, M1 - +++
tetrahydrofurano-furanes : B2,G2,M2 - +
Toxic effects: caused by epoxy metabolites (e.g. AFB1  13,14 epoxy-AFB1) liver damage, mitosis
inhibition, immune suppression, hepatocarcinogenic (DNA adduct formation)
Symptoms: early: lower feed intake, lower growth rate, anaemia
chronic: liver steatosis, immune suppression, impaired hatchability
SENSITIVE SPECIES:
- young animals
- monogastrics ( domestic chicken and pheasant chicken less sensitive)
STERIGMATOCYSTINS - Aspergillus versicolor, Aspergillus flavus, Aspergillus parasiticus
MAIN SOURCES : cereal grains
OPTIMAL TEMPERATURE FOR TOXIN PRODUCTION: 20-25 oC
CHEMICALLY: furano-furanes
TOXIN: Sterigmatocystin – low toxicity compound but average amount in feeds is higher than other
mycotoxins - potentially harmful
MAIN TOXIC EFFECT: hepatocarcinogenic ( relative toxicity is about 10 % of AFB1 )
OCHRATOXINS - Aspergillus ochraceus, Penicillium verrucosum
MAIN SOURCES: cereal grains (mainly barley)
OPTIMAL TEMPERATURE OF TOXIN PRODUCTION : 25 oC
CHEMICALLY: dicoumarol + -phenylalanine
TOXIN: Ochratoxin-A
MAIN TOXIC EFFECTS:
- kidney damage (inhibition of kidney tubular cell membrane bound enzymes )
- pancreas damage – insulin secretion also impaired
- hyperglucoseuria + hyperglucosaemia
33
SYMPTOMS: - low productivity + high feed conversion
- gout (accumulation of uric acid crystals in body cavity and also in joints)
RUBRATOXINS - Penicillium rubrum, Penicillium purpurogenum
TOXIN: rubratoxin B
TOXIC EFFECTS: hepatotoxic + teratogenic
(potentiates the effect of AFB1 and OTA)
ERGOT ALKALOIDS - Claviceps purpurea
SOURCES: rye – some cases wheat oat, barleyRYE
TOXINS : lisergic acid – amines, ergotoxin, ergotamin
SYMPTOMS OF TOXICITY:
Acute: vomiting, diarrhoea, spasms, ataxia, abortion
Chronic: gangrena – necrosis on ear, tail, comb
ZEARALENONE (F-2 TOXIN) - Fusarium graminearum, Fusarium culmorum, Fusarium equiseti,
Fusarium sambucinum, Fusarium scirpi
SOURCE: cereal grains – mainly corn
OPTIMAL TEMPERATURE FOR TOXIN PRODUCTION: 20-25 oC
CHEMICALLY: resorcyclic acid lactone
TOXICITY: practically non toxic – per os application
estrogen-like effect – genitotoxic ( prepubertal gilts)
FUMONISINS – Fusarium moniliformae (Alternaria alternata – fumonisin-like toxic compounds)
TOXINS: fumonisin B1, fumonisin B2
OPTIMAL TEMPERATURE FOR TOXIN PRODUCTION: 20 - 25 oC
SOURCES: cereal grains – mainly corn
TOXIC EFFECT: inhibition of sphingolipid biosynthesis
TOXIC SYMPTOMS: feed refusal, exudative lung
FUSARIC ACID - Fusarium spp. – mainly Fusarium moniliformae
CHEMICALLY: 5-butylpiconyl acid
SOURCES: Fusarium contaminated cereal grain – mainly corn
34
TOXIC EFFECTS:
- lowering blood pressure
- increase brain serotonin and tryptophan content
- inhubution of dopamine- - hydroxylase
TOXIC SYMPTOMS: vomiting, diarrhoea, ataxia, depression,
impaired cell-mediated immune response
TRICHOTHECENES
TOXINS:
T-2 toxin
HT-2 toxin ( metabolite of T-2 toxin )
neosolaniol (NS)
diacetoxyscirpenol (DAS)
desoxynivalenol (DON) - common name: vomitoxin
fusarenon - X (F-X)
nivalenol (NIV)
SPECIES:
Fusarium tricinctum
(T-2, HT-2, NS)
Fusarium sporotrichioides
(T-2, HT-2, NIV)
Fusarium poae
(T-2, HT-2, NIV)
Fusarium graminearum
(DON, DAS, T-2)
Fusarium oxysporum
(F-X)
Fusarium solani
(DAS, F-X)
Fusarium nivale
(F-X, NIV)
Trichoderma viridae
(T-2)
OPTIMAL TEMPERATURE FOR TOXIN PRODUCTION: 10-15 oC (except DON: 20-30 oC )
CHEMICALLY: spiro- epoxy –sesquiterpenes
SOURCES: wheat, corn, rye, barley, soybean, rice
MAIN BIOCHEMICAL EFFECT OF TRICHOTHECENES: - inhibition of protein synthesis
SYMPTOMS OF TOXICITY: lower production traits – feed refusal
diarrhoea, vomiting
impaired immune response
35
MACROCYCLIC TRICHOTHECENES
TOXINS: verrucarins, roridines, satratoxins
SPECIES: Stachybotris chartarum, Myrothecium verrucaria, Myrothecium roridum
OPTIMAL TEMPERATURE FOR TOXIN PRODUCTION: 20 - 25 oC
SOURCES: straw anad hay (mainly barley straw)
CHEMICALLY: spirocyclic – lactones
TOXIC EFFECTS: similar than trichotecenes but about 10 times more harmful
mainly – inhibition of immune response
POTENTIAL TREATMENT AND PREVENTION
1. Prevention: suitable agro-technique
inhibition of mould reproduction
2. During storage - proper moisture and humidity control

organic acids – mainly propionic acid
3. Treatment: there are no specific therapy available against mycotoxins
Highly nutritious diet – toxin free or low toxin level
Antioxidants – for prevention only
+ Improve cell-mediated immune response ( e.g. ascorbic acid )
Oral adsorbents – charcoal, bentonite, zeolite, hydrated sodium/ calcium/ aluminiumsilicates
Mannan – oligosaccharides
4. Decontamination of feeding stuffs :
4.1. Heat treatment – not useful (mycotoxins are very stable molecules )
4.2. Strong alkaline treatment – neutralisation !!
4.3. Oxidant treatment – hydrogen peroxide – rancidity of fats !!!
4.4. Sodium- hypochlorite – neutralisation !!
5. Inactivation: enzyme addition for decomposition of mycotoxins
- ruminants – rumen microflora metabolise most mycotoxins
- monogastrics – specific enzyme addition (e.g. epoxidases – trichothecenes
esterase – zearalenone )
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