View
7
Download
0
Category
Preview:
Citation preview
Mycotoxin In PoultryGeneral Overview
› Introduction
› Fungi species
› Fungi growth
› Agronomic factors affecting mycotoxin formation in the field
› Principle factors influencing mycotoxin production
› Mycotoxin types
› Introduction
› Fungi species
› Fungi growth
› Agronomic factors affecting mycotoxin formation in the field
› Principle factors influencing mycotoxin production
› Mycotoxin types
Human First Discovery
• Human cases of ergotism or St. Anthony's Fire have been described in Europe since the Middle Ages.
• It is known now to be caused by alkaloids produced in rye by the mould Claviceps purpurea.
Avian First Discovery England 1960, • An outbreak of Turkey X disease and
the subsequent discovery of the aflatoxins stimulated great interest in the field of mycotoxin research (Bullerman, 1979).
• Since then, many more mycotoxins have been discovered, such as;1. Trichothecenes2. Zearalenone3. Ochratoxins4. Fumonisins
What Are Mycotoxins?
› The word mycotoxin stems from the Greek word "mykes", meaning mould,and "toxicum" meaning poison.
› Mycotoxins are toxic secondary metabolites produced by fungi growing oncrops whether;
1. In the field
2. During handling
3. During storage
Cont. …
Characteristics of Mycotoxins:
1. There are hundreds of known mycotoxins.
2. They are chemically different.
3. They vary greatly in their severity.
4. Their molecular weight ranges from 200 to 500 kD.
Mycotoxins Host Affinity
› All poultry species are affected by mycotoxins.
› There are some species differences have been reported, such as duckswhom are particularly sensitive towards aflatoxin.
Mycotoxin Affection
Mycotoxins enter the animal production system via:
1. Feed (concentrate, silage or forage)
2. Bedding.
Mycotoxin Negative Effect
› Mycotoxins negatively affect:
1. Animal performance
2. Animal health
3. Product quality
› Mycotoxin control is crucial for:
1. Production economics
2. Animal welfare
3. Product quality
4. Food safety
Cont. …
› Mycotoxins exert their effects through 4 primary mechanisms:
1. Reduction of feed intake or feed refusal.
2. Alteration in nutrient content of feed in terms of nutrient absorptionand metabolism.
3. Effects on the endocrine and exocrine systems.
4. Suppression of the immune system.
Cont. …
1. Poor growth
2. Reduced egg production
3. Increase feed conversion
4. Increased mortality
5. Poor egg shell quality
6. Reduced fertility
7. Leg problems
8. Carcass condemnation
9. Increased susceptibility to disease
Diagnosing Mycotoxicosis
› Mycotoxicosis often lead to unspecific symptoms, which can also be causedby many other factors, making if difficult to diagnose mycotoxin problems.
• Moderate mycotoxicosis has general unspecific symptoms as:
1. Reduced performance
2. Impaired immunity
• Sever mycotoxicosis has more specific symptoms.
› Further difficulties in mycotoxicosis diagnoses can be caused by secondarysymptoms resulting from opportunistic disease related to the suppression ofthe immune system following mycotoxin exposure.
Cont. …
› In order to effectively identify mycotoxicosis, experience with mycotoxin-affected animals is important.
› This experience, combined with adequate feed and tissue analyses whichprovide the basis for the most accurate diagnosis of mycotoxicosis.
› Introduction
› Fungi species
› Fungi growth
› Agronomic factors affecting mycotoxin formation in the field
› Principle factors influencing mycotoxin production
› Mycotoxin types
Fungi Species
› Fungal species are often divided into two groups:
1. Field fungi
2. Storage fungi
› Field fungi invade the seeds while the crop isstill in the field.
› They require high moisture conditions (20-21%).
› These include species of:
– Fusarium
– Alternaria
– Clodosporium
– Diplodia
– Gibberella
– Helminthosporium
Field Fungi
Cont. …
Storage Fungi
› They invade grains or seeds during storage.
› They need less moisture than field fungi (13-18%)
› Usually do not present any serious problembefore harvest.
› Storage fungi include species of:
– Aspergillus
– Penicillium
› Introduction
› Fungi species
› Fungi growth
› Agronomic factors affecting mycotoxin formation in the field
› Principle factors influencing mycotoxin production
› Mycotoxin types
Fungal Growth
› Moulds grow by producing long filaments called hyphae
• Hyphae form a network.
• The network is responsible for cementing kernels together.
› This complex forms clumps of grain that cannot beseparated.
Cont. …
› Grain-mould fungi also produce spores capable of aerial dispersal in the field.
› Masses of these spores give the mould a characteristic color.
› Spores can lay dormant for months or years until the proper conditions for fungal development are available.
› Stress and subsequently reduced vigouroften predispose plants to infestation and colonization by toxigenic fungi.
Field Fungi
Predisposing Factors For Fungal growth
Storage Fungi
Fungal infection and mycotoxin production result from a complex interaction between:
1. Moisture
2. Temperature
3. Substrate
4. Oxygen (O2)
5. Carbon dioxide (CO2) concentration
6. Fungal abundance
7. Insect presence
Fungi Ideal Growth Conditions
The ideal growth conditions are:
1. Environmental humidity
2. Temperature
3. pH and Oxygen
1- Environmental Humidity
› The most interesting benchmark for fungal growth is humidity or free water.
› According to the behavioral differences related to water availability, fungispecies can be classified as follows:
Cont. …
Hydric
• The spore can only germinate at free water levels above 90%.
• The optimal growth takes place at 100%.
Medium level
• The spores germinate at free water levels between 80% and 90%.
• The best and optimal growth takes place at 95% - 100%.
Xerofile
• The spores germinate at free water levels less than 80%.
• The best and optimum growth takes place at 95%.
Cont. …
61% ---- The minimum level for all fungi.
78% ---- The minimum level for Toxigenic species.
7% ---- Fungi can grow only in grains with high levels of oil (e.g. peanuts)
2- Temperature
› The ideal temperature: 15 - 30°C.
› Optimal values of 20-25°C.
Cont. …
Low Temperature Exception1. Cladosporium herbarium have an apparent growth at -6°C.
2. Penicillium can develop in frozen fish at -20°C.
3. Rhizopus nigricans, Mucor mucedo, Aspergillus niger, Aspergillus glaucus can persistafter immersion for 77 hours in liquid hydrogen at -253°C and for 492 hours in liquidair at -190°C.
High Temperature Exception1. Aspergillus fumigatus, can contaminate respiratory tract at body temperature.
2. Monilia sitophila can survive at 35-40°C (typical contaminant of bread)
3- pH and Oxygen
pH
– Ideal pH: 4 - 8.
– Some moulds can grow at lower or higher values by modifying theacidity of the medium during their development.
O2
– Moulds are generally aerobic organisms that develop above the surfaceof the medium.
– Some species can however develop in deep mediums or in liquidmediums such as Stachybotrys, with a low oxygen rate.
› Introduction
› Fungi species
› Fungi growth
› Agronomic factors affecting mycotoxin formation in the field
› Principle factors influencing mycotoxin production
› Mycotoxin types
Agronomic Factors Affecting Mycotoxin Formation in The Field
› As temperature and moisture levels are keyfactors for fungal growth and subsequentmycotoxin production, the climate plays a key rolein the occurrence of mycotoxins.
› Crop surveys show large variations incontamination levels from one year to anotherdue to varying climatic conditions.
Cont. …
› In addition to climatic conditions, agronomic practices also have apronounced effect on mycotoxin formation as they affect:
1. Presence of fugal spores in the field.
2. Fungal growth.
Key Agronomic Factors to Affect Mycotoxin Presence and Concentration Significantly
› Three key agronomic factors have been shown to affect mycotoxin presenceand concentration significantly:
1. Crop presence and rotation
2. Soil cultivation
3. Crop and crop variety
Cont. …
1. Crop presence and rotation:
› Monocultures (planting of closely related crops one after the other) willenhance the risk of mycotoxin formation.
› Spores will transfer to the subsequent crop and thus allow fungal growthto establish quickly and strongly.
2. Soil cultivation:
› Ploughing harvest residues will reduce spore contamination of thesubsequent crop and thus reduce fungal infestation and mycotoxinformation.
› No-till systems will enhance the risk.
Cont. …
3. Crop and crop variety
› Crop varieties that are more resistant to fungal foliar diseases reducefungal infection and thus mycotoxin formation of the crop.
Cont. …
› Mycotoxins are very stable.
› They will persist during storage as they are independent of storageconditions.
› Because there are no efficient decontamination procedures are availabletoday, most of the mycotoxins that are present at the time of harvest willreach the final animal diet during feed consumption.
› Introduction
› Fungi species
› Fungi growth
› Agronomic factors affecting mycotoxin formation in the field
› Principle factors influencing mycotoxin production
› Mycotoxin types
Principal Factors Influencing Mycotoxin Production
These factors are;
1. Intrinsic factors
– They are connected to the fungal stock.
2. Extrinsic factors
– The are environmental conditions.
1- Intrinsic Factors
Intrinsic factors, connected to the fungal stock
1. The power of generating toxins
– It varies inside each fungi from 1 to 103-104.
2. The fungal species
– It determines type of mycotoxin produced.
3. The initial contamination
– It influences the amount of mycotoxins produced.
2- Extrinsic Factors
1. Chemical, physico-chemical and physical factors.
2. Biological factors.
Cont. …
1. Chemical, physico-chemical and physical factors such as:
1. Humidity – level of free water
2. Temperature
3. Gas composition (atmosphere)
4. Substrate
Chemical, Physico-chemical and Physical Factors
Chemical, physico-chemical and physical factors;
1. Level of free water (humidity)
2. Temperature
3. Oxygen
4. Type of substrate
Cont. …
1. Level of free water
› Toxin production is improved at levels of free water of 90%.
› Aspergillus flavus can start to produce aflatoxin at 83%.
› A. ochraceus needs at least 97% to produce ochratoxins.
› The humidity of the substratum is the principal factor to be consideredin the prevention of contamination and its control has becomefundamental in feed production.
Cont. …
2. Temperature
– It is difficult to define temperature values to control mycotoxinproduction.
– Aspergillus flavus produces aflatoxins at 10°C - 25°C.
– Fusarium tricinctum produce T2 toxin at 1°C - 4°C, up to 15°C.
– Aspergillus ochraceus produces ochratoxin from 12°C - 20°C up to 30°C.
– Penicillium viridicatum produces ochratoxin between 4°C - 31°C.
Cont. …
2. Oxygen
– Oxygen concentration and the acidity of substratum are not relevant formycotoxin production.
3. Type of substrate
– Some types of substrate may help improve mycotoxin production;
1. Vegetal, more than the animal substrates.
2. Starch.
3. Zinc, only referred to the aflatoxin production.
4. Cereals, oleaginous seeds and dried fruit are the foods most frequentlycontaminated by aflatoxins.
5. The more frequent products contaminated with mycotoxins are maize,peanuts and cotton seeds.
Cont. …
2. Biological factors, such as:
1. Insects
› Act as a vectors of fungal spores.
› Acts as vectors responsible for mechanical damage to the caryopsis,favoring the entry of moulds.
2. Microbiological flora
3. Competition between mycological strains
4. Plant stress
› Introduction
› Fungi species
› Fungi growth
› Agronomic factors affecting mycotoxin formation in the field
› Principle factors influencing mycotoxin production
› Mycotoxin types
Types Of Mycotoxins
Fungi proliferate Grow coloniesMycotoxin levels become high
then then
Cont. …
Cocktails of mycotoxins
Storage fungi
Field fungi
Cont. …
Although several hundred mycotoxins are known, the mycotoxins of mostconcern, based on their toxicity and occurrence, are:
1. Aflatoxin
2. Trichothecenes (DON, T-2 toxin, DAS, etc)
3. Ochratoxin A
4. Zearalenone
5. Fumonisin
6. Moniliformin
Cont. …
Mycotoxin Fungi Produced Commodities affected
AflatoxinAspergillus flavusAspergillus parasiticus
Corn, cotton seed, peanuts, soy
Ochratoxin AAspergillus ochraceusAspergillus nigriPenicillium verrucosum
Wheat, barley, oats, corn, others
Trichothecenes (DON, T-2, DAS, etc)
Fusarium graminearumFusarium culmorum
Corn, wheat, barley
Zearalenone Fusarium graminearum Corn, wheat, barley, grass
FumonisinFusarium verticillioidesFusarium proliferatum
Corn
Moniliformin Fusarium moniliforme Corn
PR toxin, patulin Penicillium roqueforti Silage, Grass
Aflatoxin
Production
› Aflatoxins are of concern in warm and humid climatic conditions.
› Although aflatoxins are not considered to be a major problem in cold ormore temperate regions, caution must be exercised in colder climates whenusing feedstuffs imported from warm and humid countries.
Host Sensitivity
› Among poultry, ducks are the most susceptible to aflatoxin, followed byturkeys, broilers, laying hens and quail.
Effects
Aflatoxins are hepatotoxic
1. Fatty changes - causing hepathocyte degeneration - Hepatic necrosis
2. Altered liver function.
3. Suppression of hepatic protein synthesis is the main factor resulting ingrowth suppression and reduced egg production.
4. Interfere with vitamin D metabolism, contributing to reduced bonestrength and leg weakness.
5. Reduce bile salt production, and in turn negatively affects lipiddigestion.
6. Reduce metabolism of other minerals including iron, phosphorus andcopper.
Cont. …
Blood vessels
› Increases the fragility of capillaries
› Reduce prothrombin levels.
Cont. …
› Due to the transfer of aflatoxin into edible products and its carcinogeniceffects, most countries have set upper legal limits for aflatoxin in feed.
Clinical Signs of Aflatoxin Toxicity
1. Decrease weight gain - anorexia – increase FCR
2. Fatty liver - Liver necrosis - Bile duct hyperplasia
3. Increased mortality
4. Immune suppression - increased disease susceptibility
5. Specific visceral hemorrhage
6. Leg weakness and reduced bone strength
7. 'Pale bird syndrome'
8. Increased incidence of bruising and downgrading
9. Embryo toxicity - Reduced fertility and hatchability
10. Decreased egg production
Ochratoxin
Production
› Ochratoxins are important storage toxins.
› They are produced by different fungi and are prevalent in temperate as wellas in tropical regions.
› Ochratoxin A is the most important of the ochratoxins.
OTA Pharmacokinetics
› Absorption
– Following oral consumption of OTA-contaminated feed, rapid absorptioninto the blood via the gastrointestinal tract.
› Distribution
– Based on its polar composition, OTA is widely distributed throughout thebody fluids, in organs and tissues of rats, pigs, rabbits and chickens.
› Elimination
– OTA is slowly eliminated in urine and feces.
Effects
› Ochratoxin A is nephrotoxic
– Proximal tubules are mainly affected and the kidney is pale and grosslyenlarged.
– In acute cases, mortalities occur due to acute renal failure.
› As with aflatoxin, fatty liver can also occur due to ochratoxin exposure.
› In young chicks, ochratoxin A is approximately three times more toxic thanaflatoxin.
Clinical Signs Of Ochratoxin Toxicity
1. Reduced feed intake - Reduced growth rate – Reduced egg production.
2. Reduced feed conversion efficiency.
3. Mortality due to acute renal failure - Pale and grossly enlarged kidney.
4. Polyurea with large volumes of wet faeces.
5. Fatty liver.
Cont. …
6. Urate deposition in joints and abdominal cavity (at high exposure levels)
7. Depletion of lymphocytes and with strong suppression of cellularimmunity.
8. Poor egg shell quality and higher incidence of eggs with blood spots.
9. Reduced embryo viability - Decreased hatchability.
10. Reduced feathering.
Trichothecenes
Trichothecenes (T-2 toxin, diaceptoxyscripenol (DAS), deoxynivalenol (DON), HT-2 toxin, etc)
› Trichothecenes are typical field mycotoxins.
› They are produced on crops entering the feed via contaminated ingredients.
› Poultry are most sensitive to T-2 toxin and DAS.
Clinical Signs of Trichothecenes Toxicity
1. Trichothecenes are proven tissue irritants (Oral lesions, dermatitis andintestinal irritation)
a) Oral lesions
› Circumscribed proliferate yellow caseous plaques occurring at themargin of the beak, mucosa of the hard palate and the anglebetween the mouth and the tongue.
b) Gizzard erosion
› Necrosis of proventricular mucosa
2. Loss of appetite
– Reduced feed intake - Reduced weight gain
Cont. …
3. Immune suppression
– It affects cellular immune response by direct effects on bone marrow,spleen, lymphoid tissues, thymus and intestinal mucosa, where activelydividing cells are damaged.
– Reduced vaccination response.
4. Reduced egg production - Poor shell quality.
5. Regression of ovaries.
6. Reduced female fertility and hatchability of fertile eggs.
7. Tibia dyschondroplasia.
8. Increased liver weight.
Zearalenone (ZEA)
Zearalenone (ZEA)
› ZEA has limited toxicity to birds.
› Zearalenone often occurs with DON in naturally-contaminated cereals.
› Zearalenone is responsible for reproductive disorders due to its oestrogeniceffect at high concentrations.
› At high concentrations the following symptoms have been observed:
1. Vent enlargement
2. Enhanced secondary sex characteristics
Fumonisin
Fumonisin
› Broilers and turkeys are resistant to acute fumonisin’s toxicity.
Clinical Signs of Fumonisin Toxicity
1. Spiking mortality (paralysis, extended legs and neck, wobbly gait,gasping)
2. Reduced growth rate.
3. Increased organ weights.
4. Hepatocellular hyperplasia.
5. Poor vaccination response.
scientific Office:12 Abbas El Akad St., 9th district, El Obour City, EgyptTel. and fax: +2 02 43126096Cellular: +2 0120 51 00 700E-mail: info@solveda.net
Factory192 small industrial area, El Obour City B/C, EgyptTel.: (+2) 02 4487 40 50(+2) 02 4487 44 80Website: www.solveda.net
Recommended