mycotoxicosis in poultry_general overview

Mycotoxin In PoultryGeneral Overview

Plan Of Talk

Introduction Fungi species Fungi growth Agronomic factors affecting mycotoxin formation in the field Principle factors influencing mycotoxin production Mycotoxin types

Plan Of Talk

Introduction Fungi species Fungi growth Agronomic factors affecting mycotoxin formation in the field Principle factors influencing mycotoxin production Mycotoxin types

Mycotoxins … 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.

Mycotoxins … 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, such as trichothecenes, zearalenone, ochratoxins and fumonisins have been discovered.

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 on crops whether;1. In the field2. During handling3. 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.

– Species differences have been reported.

– Ducks for example 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 performance2. Animal health 3. Product quality

Mycotoxin control is crucial for:4. Production economics5. Animal welfare6. Product quality 7. 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 absorption

and metabolism.3. Effects on the endocrine and exocrine systems.4. Suppression of the immune system.

Cont. …

1. Poor growth2. Reduced egg production3. Reduced feed conversion4. Increased mortality5. Poor egg shell quality6. Reduced fertility7. Leg problems8. Carcass condemnation9. Increased susceptibility to disease

Diagnosing Mycotoxicosis

Mycotoxicosis often lead to unspecific symptoms, which can also be caused by many other factors, making if difficult to diagnose mycotoxin problems. – Moderate mycotoxicosis has general unspecific symptoms as:

• Reduced performance • Impaired immunity

– Sever mycotoxicosis has more specific symptoms.

Cont. …

Further difficulties in mycotoxicosis diagnoses can be caused by secondary symptoms resulting from opportunistic disease related to the suppression of the 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, provide the basis for the most accurate diagnosis of mycotoxicosis.

Plan Of Talk

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 fungi2. Storage fungi

Field Fungi

Field fungi invade the seeds while the crop is still in the field.

They require high moisture conditions (20-21%).

These include species of:1. Fusarium2. Alternaria3. Clodosporium4. Diplodia5. Gibberella 6. Helminthosporium

Storage Fungi

They invade grains or seeds during storage.

They need less moisture than field fungi (13-18%)

Usually do not present any serious problem before harvest.

Storage fungi include species of:1. Aspergillus 2. Penicillium

Plan Of Talk

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 be separated. Grain-mould fungi also produce spores

capable of aerial dispersal in the field.

Cont. …

Masses of these spores give the mould a characteristic colour. Spores can lay dormant for months or years until the proper

conditions for fungal development are available.

Predisposing Factors For Fungal growth

Under field conditions, Stress and subsequently reduced vigour often predispose plants to infestation and colonization by toxigenic fungi.

Cont. …

In stored grain, Fungal infection and mycotoxin production result from a complex interaction between:

1. Moisture2. Temperature3. Substrate4. Oxygen (O2) 5. Carbon dioxide (CO2) concentration6. Fungal abundance 7. Insect presence

• Insects can influence a differentiation of fungal species, that is a specific insect determines the presence of a specific fungal species.

Fungi Ideal Growth Conditions

The ideal growth conditions are:1. Environmental humidity2. Temperature3. pH and Oxygen

Environmental Humidity

The most interesting benchmark for fungal growth is humidity or free water.

According to the behavioral differences related to water availability, fungi species 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)

Temperature

The ideal temperature: 15 - 30°C. Optimal values of 20-25°C.

Cont. …Low Temperature Exception

1. 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 persist after immersion for 77 hours in liquid hydrogen at -253°C and for 492 hours in liquid air at -190°C.

Cont. …High Temperature Exception

1. Aspergillus fumigatus, can contaminate respiratory tract at body temperature.

2. Monilia sitophila can survive at 35-40°C (typical contaminant of bread)

pH and Oxygen

pH Ideal pH: 4 - 8. Some moulds can grow at lower

or higher values by modifying the acidity of the medium during their development.

Cont. …

O2 Moulds are generally aerobic organisms that

develop above the surface of the medium. Some species can however develop in deep

mediums or in liquid mediums such as Stachybotrys, with a low oxygen rate.

Plan Of Talk

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 key factors for fungal growth and subsequent mycotoxin production, the climate plays a key role in the occurrence of mycotoxins.

Crop surveys show large variations in contamination levels from one year to another due to varying climatic conditions.

Cont. …

In addition to climatic conditions, agronomic practices also have a pronounced effect on mycotoxin formation as they affect:1. Presence of fugal spores in the field.2. Fungal growth.

Three key agronomic factors have been shown to affect mycotoxin presence and 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) will enhance the risk of mycotoxin formation.

Spores will transfer to the subsequent crop and thus allow fungal growth to establish quickly and strongly.

Cont. …

2. Soil cultivation: Ploughing harvest residues will

reduce spore contamination of the subsequent crop and thus reduce fungal infestation and mycotoxin formation.

No-till systems will enhance the risk.

Cont. …

3. Crop and crop variety Crop varieties that are more resistant to fungal foliar

diseases reduce fungal infection and thus mycotoxin formation of the crop.

Cont. …

Mycotoxins are very stable. They will persist during storage as they are independent of

storage conditions. Because there are no efficient decontamination procedures

are available today, most of the mycotoxins that are present at the time of harvest will reach the final animal diet during feed consumption.

Plan Of Talk

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, connected to the fungal stock.2. Extrinsic factors, i.e. environmental conditions.

Intrinsic Factors

Intrinsic factors, connected to the fungal stock1. 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.

Extrinsic Factors

1. Chemical, physico-chemical and physical factors.2. Biological factors.

Cont. …

Chemical, physico-chemical and physical factors such as:1. Humidity2. Free water 3. Temperature4. Substrate5. Gas composition (atmosphere)6. Mechanical damages to the caryopsis

Cont. …

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 strains4. Plant stress

Chemical, Physico-chemical And Physical Factors

Chemical, physico-chemical and physical factors;1. Level of free water (humidity)2. Temperature3. Oxygen4. Type of substrate

Cont. …

1. Level Of Free Water Toxin production is improved by 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 considered in the prevention of contamination and its control has become fundamental in feed production.

Cont. …

2. Temperature It is difficult to define temperature values to control

mycotoxin production. 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. …

3. Oxygen Oxygen concentration and the acidity of substratum are

not relevant for mycotoxin production.

Cont. …

4. Type of substrateSome 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

frequently contaminated by aflatoxins. 5. The more frequent products contaminated with mycotoxins are

maize, peanuts and cotton seeds.

Plan Of Talk

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 colonies Mycotoxin levels become high

then then

Cont. …

Cocktails of mycotoxins

Storage fungi

Field fungi

Cont. …

Although several hundred mycotoxins are known, the mycotoxins of most concern, based on their toxicity and occurrence, are:

1. Aflatoxin2. Trichothecenes (DON, T-2 toxin, DAS, etc)3. Ochratoxin A4. Zearalenone5. Fumonisin6. Fumonisin7. Moniliformin

Cont. …Mycotoxin Fungi Produced Commodities affected

Aflatoxin Aspergillus 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

Fumonisin Fusarium verticillioidesFusarium proliferatum Corn

Moniliformin Fusarium moniliforme Corn

PR toxin, patulin Penicillium roqueforti Silage, Grass

Aflatoxin

Aflatoxin

Aflatoxins are of concern in warm and humid climatic conditions.

Although aflatoxins are not considered to be a major problem in cold or more temperate regions, caution must be exercised in colder climates when using feedstuffs imported from warm and humid countries.

Host Sensitivity

Among poultry, ducks are the most susceptible to aflatoxin, followed by turkeys, broilers, laying hens and quail.

Effects

Aflatoxins are hepatotoxic1. Fatty changes - causing hepathocyte degeneration - Hepatic necrosis2. Altered liver function. 3. Suppression of hepatic protein synthesis is the main factor resulting

in growth suppression and reduced egg production. 4. Interfere with vitamin D metabolism, contributing to reduced bone

strength and leg weakness. 5. Reduce bile salt production, and in turn negatively affects lipid

digestion.6. Reduce metabolism of other minerals including iron, phosphorus

and copper.

Cont. …

Blood vessels Increases the fragility of capillaries Reduce prothrombin levels.

Due to the transfer of aflatoxin into edible products and its carcinogenic effects, most countries have set upper legal limits for aflatoxin in feed.

Clinical Signs Of Aflatoxin Toxicity

1. Decrease weight gain - anorexia – increase FCR2. Fatty liver - Liver necrosis - Bile duct hyperplasia3. Increased mortality4. Immune suppression - increased disease susceptibility5. Specific visceral haemorrhage6. Leg weakness and reduced bone strength7. 'Pale bird syndrome'8. Increased incidence of bruising and downgrading9. Embryo toxicity - Reduced fertility and hatchability10. Decreased egg production

Ochratoxin

Ochratoxin

Ochratoxins are important storage toxins. They are produced by different fungi and are prevalent in

temperate as well as in tropical regions. Ochratoxin A is the most important of the ochratoxins.

Effects

Ochratoxin A is nephrotoxic– Proximal tubules are mainly affected and the kidney is pale and grossly

enlarged. – 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 than aflatoxin.

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 cellular immunity.

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 and intestinal irritation.

2. Loss of appetite– Reduced feed intake - Reduced weight gain

3. Oral lesions: circumscribed proliferate yellow caseous plaques occurring at the margin of the beak, mucosa of the hard palate and the angle between the mouth and the tongue.

4. Gizzard erosion - Necrosis of proventricular mucosa

Cont. …

5. Immune suppression– It affects cellular immune response by direct effects on

bone marrow, spleen, lymphoid tissues, thymus and intestinal mucosa, where actively dividing cells are damaged.

– Reduced vaccination response.6. Reduced egg production - Poor shell quality.7. Regression of ovaries.8. Reduced female fertility and hatchability of fertile eggs.9. Tibia dyschondroplasia.10. Increased liver weight.

Zearalenone (ZEA)

Zearalenone (ZEA)

Zearalenone often occurs with DON in naturally-contaminated cereals.

Zearalenone is responsible for reproductive disorders due to its oestrogenic effect at high concentrations.

ZEA has limited toxicity to birds. At high concentrations the following symptoms have been

observed:1. Vent enlargement2. Enhanced secondary sex characteristics

Fumonisin

Fumonisin

Broilers and turkeys are resistant to acute fumonisins 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.