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SZENT ISTVÁN UNIVERSITY FACULTY OF AGRICULTURAL AND ENVIRONMENTAL SCIENCES DEPARTMENT OF NUTRITION
GENERAL AND MOLECULAR FEED TOXICOLOGY
Course booklet
Miklós Mézes Ph.D., DSc., Professor of Nutrition
GÖDÖLLŐ 2004
1 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
2 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
3 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 me- chanism (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 steroid metabolism sulphotransferase (e.g. estrone sulphate - faeces)
Xenobiotics 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
4 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 neces- sarily 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
5 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 - S-sulphoglutathione : GSSO3H
GSH + xenobiotic (electrophilic compound ) GSH-transferase GSH-conjugate
6
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 + e - - e + nH2O e aq + + H2O + H2O OH + H3O - - e aq + H2O H + OH
The 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 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
7 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-formamido- pyrimidine 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 A : T T: A G :C C : G A : T C : G G : C A : T 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
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
8 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
9 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
THERAPY : addition of folic acid, vitamin B12, Met
10 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)
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
11 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
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
12 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)
2+ CHROMIUM (Cr 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
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)
13 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) 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)
14 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
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--hydroxy- lase), retarded growth (deficiency of cytochrome-c-oxidase)
NICKEL - route of toxicity mainly with feed and water (absorption : 10 % )
15 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 - 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
16 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
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
17 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
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
18 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 CATTL SHEEP PIG POULTRY HORSE RABBIT E Aluminium 1000 1000 (200) 200 (200) (200) Antimony - - - - - 70-150 Arsenic (inorg.) 50 50 50 50 (50) 50 Arsenic (org.) 100 100 100 100 (100) (100) Barium (20) (20) (20) (20) (20) (20) Bismuth (400) (400) (400) (400) (400) 2000 Boron 150 (150) (150) (150) (150) (150) Bromium 200 (200) 200 2500 (200) (200) Cadmium 0,5 0,5 0,5 0,5 (0,5) (0,5) Calcium (%) 2 2 1 1,2 - 4 2 2 Chromium (1000) (1000) (1000) 1000 (1000) (1000) Cobalt 10 10 10 10 (10) (10) Copper 100 25 250 300 800 200 Fluoride 40-100 60-150 150 150-200 (40) (40) Iodine 50 50 400 300 5 - Iron 1000 500 3000 1000 (500) (500) Led 30 30 30 30 30 (30) Magnesium ( %) 0,5 0,5 (0,3) (0,3) (0,3) (0,3) Manganese 1000 1000 400 2000 (400) (400) Mercury 2 2 2 2 (2) (2) Molibdenum 10 10 20 100 (5) 500 Nickel 50 (50) (100) (300) (50) (50) Phosphorus( %) 1 0,6 1,5 0,8 -1 1 1 Potassium (%) 3 3 (2) (2) (3) (3) Selenium (2) (2) 2 2 (2) (2) Silica ( %) (0,2) 0,2 - - - - Silver - - (100) 100 - - NaCl ( % ) 4-9 9 8 2 (3) (3) Strontium 2000 (2000) 3000 10000 (2000) (2000) Sulphur ( %) (0,4) (0,4) - - - - Tin ------Titan ------Wolfram (20) (20) (20) 20 (20) (20) Uranium ------Vanadium 50 50 (10) 10 (10) (10) Zinc 500 300 1000 1000 (500) (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
SAPONINS
22 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 DIQUAT:
27 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
PLACE OF DAMAGE PERSISTENCY OPTIMAL HUMIDITY
29 (Christensen) DURING STORAGE (Pelhate) (Pelhate) GROUND MOULDS EPHEMER HIGROPHYL Alternaria Alternaria Fusarium Fusarium Fusarium Mucorales Cladosporium Trichoderma Stachybotrys STORE MOULDS MESOBIONTIC MESOPHYL Aspergillus Cladosporium Cladosporium Penicillium Alternaria Mucorales Aspergillus Penicillium PERSISTENT SPECIES XEROPHIL SPECIES Aspergillus Aspergillus glaucus Penicillium Aspergillus restrictus Mucorales Aspergillus versicolor
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 - Effect of mould (mycelium – cell wall components – allergenic) vs. effect of toxin - Mould contaminated feed – lower nutrient content (mainly fat – lipase activity of moulds)
30 - 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 MOULD SPECIES HEPATOTOXIC AFLATOXINS ASPERGILLUS FLAVUS HEPATOCARCINOGENIC STERIGMATOCYSTIN ASPERGILLUS PARASITICUS ASPERGILLUS VERSICOLOR TERATOGENIC AFLATOXIN B1 ASPERGILLUS FLAVUS OCHRATOXIN A ASPERGILLUS PARASITICUS PATULIN ASPERGILLUS OCHRACEUS RUBRATOXIN B PENICILLIUM SP NEUROTOXIC CITREOVIRIDIN PENICILLIUM CITROVIRIDAE PATULIN ASPERGILLUS SP. PENICILLIUM SP. FUMONISIN FUSARIUM MONILIFORMAE NEPHROTOXIC OCHRATOXIN A ASPERGILLUS OCHRACEUS PENICILLIUM SP. CITRININ PENICILLIUM CITRINUM DERMATOTOXIC TRICHOTHECENES FUSARIUM SP. STACHYBOTRYS SP. MYROTHECIUM SP. EMETIC VOMITOXIN (DON) FUSARIUM SP. TRICHOTHECENES GENITOTOXIC ZEARALENON FUSARIUM SP. TREMOROGENIC PENTIREM A PENICILLIUM CYCLOPIUM FUMITREMOROGENS ASPERGILLUS FUMIGATUS PHOTOSENSIBILISING PSORALENES SCLEROTINIA SCLEROTIORUM SPORIDESMIN PITHOMYCES CHARTARUM HALLUCINOGENIC ERGOT ALKALOIDS CLAVICEPS SP. LISERGIC AMINES
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
33 - hyperglucoseuria + hyperglucosaemia 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
MACROCYCLIC TRICHOTHECENES
35 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/ aluminium- silicates 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 )
36