How do Aflatoxins originate in feed?

Susceptibility of poultry to Aflatoxins

Effects of Aflatoxins in poultry

What is the safe level for Aflatoxins

Role of UTPP-5 in improving immunity

Strategies to minimise the impact of Aflatoxins

Methods to control Fungal Growth

Mycotoxicoses

Introduction: 

Aflatoxins are group of closely related mycotoxins that are toxic and commonly found in poultry feed.  Mycotoxins are the toxic metabolites produced  by certain species of fungi during the metabolism of nutrients present in feed ingredients and feeds.  Fortunately, there are only about 50 species of fungi that produce mycotoxins, in spite of the existence of more than 10,000 species of fungi.

Mycotoxic fungi are responsible for colossal financial losses encompassing a broad spectrum of crop and animal agriculture and also chances of extending through the food chain to the consumer.  Among the 200 mycotoxins that have been described, Aflatoxins are the most frequently found mycotoxins produced by fungi Aspergillus flavus, Aspergillus parasiticus, that cause liver damage in poultry and livestock.  They lower the profitability of poultry production by decreased growth, feed conversion efficiency, egg production and break in immunity leading to heavy economic losses.

Aflatoxicosis is more common in our country, especially in areas of hot and humid conditions that encourage mold growth.

CLASSIFICATION OF AFLATOXINS:

Aflatoxins are differentiated into B (B1&B2), M(M1 & M2) and G (G1 & G2) subtypes based on structure, chromatographic and fluorescent characteristics. M1 & M2 are derivatives of B1 and are comparitively less toxic.  In terms of occurrence, B1 is more predominantly found than others and is the most toxic type to poultry & livestock including human beings.  The metabolite M1, excreted in milk in significant quantities is of great public health significance especially in case of infants and young animals.

HOW DO AFLATOXINS ORIGINATE IN FEED?

The fungal attack and production of Aflatoxins may occur during preharvest or post harvest, during storage and transportation of feed, and at farm level itself like in feed troughs.  High temperature, humidity and unseasonal rains are some of the  condusive contributing factors in the tropical regions that encourage fungal growth and aflatoxin production.  Moisture content exceeding a safe range of 8 to 12% in the feed grains may encourage fungal growth.

Aflatoxins are produced in most of the feed ingredients in livestock feeds, but most commonly in groundnut cake, maize, cottonseed cake, coconut cake.  In general, the sunflower extraction rapeseed extraction, soybean meal, bajra and deoiled rice bran contain lower level of aflatoxins.

SUSCEPTIBILITY OF POULTRY TO AFLATOXINS:

Among poultry, ducks are more susceptible for  aflatoxicosis than any other species because of higher production of hepatic microsomal enzymes that metabolize aflatoxins into harmful products leading to acute toxicity.

Generally younger age groups are more susceptible to aflatoxicosis than mature flocks, but there is considerable variation among species and breeds.  Ducklings and turkey poults are highly susceptible to aflatoxicosis.

Broilers are more susceptible than layers.

Cockerels are more prone than females. 

EFFECTS OF AFLATOXICOSIS IN POULTRY:

1.    Basically, aflatoxins are hepatotoxins that damages the principle accessory digestive gland-LIVER         and in addition, they are immunosuppressants.

2.   The adverse effects of aflatoxins are:

a.  Reduced production performances

b.  Reduced growth rate and poor carcass quality

c.  Reduced egg production and egg weight

d.  Immunosuppression leading to increased susceptibility to coccidiosis, colisepticemia  

     and salmonellosis.

e.  Affected flocks are refractory to vaccination

d.  Reduced feed intake

f.   Lowered nutrient utilization

g.  Increased mortality

f.    Increased leg problem

g.   Pale bird syndrome

WHAT IS THE SAFE LEVEL FOR AFLATOXINS?

According to experts, there is no safe level and risk depends on the amount of aflatoxins in the feed and also on presence of other mycotoxins in the feed.   The Food and Drug Administration (FDA) of  United States has set a maximum allowable level of aflatoxins at 20 ppb.  The safe level for aflatoxins vary from one form to another form due to variation in managemental conditions and disease prevalence.  The toxicity is also affected by interaction of aflatoxins with:

a.   Pathogen

b.   Environmental conditions

c.   Genetic variability

d.   Nutritional status

STRATEGIES TO MINIMISE THE IMPACT OF AFLATOXICOSIS:

Prevention is the first line of defence in minimising mold infestation and alfatoxin production.  They are:

a.   Plant breeding for mold resistance

b.   Efficient harvesting, transportation and storage practices to minimise contamination

c.   Carefully drying the grains to maintain low moisture levels

d.   Detoxify grain by using effective cleaning and segregation technique

e.   Do not store prepared feed more than a week

f.    Proper cleaning and disinfection of feeding troughs

g.  Detection of contaminated feed stuffs is the primary attack against aflatoxicosis.  Diligent  

     sampling and accurate assays are necessary to reduce the danger of mycotoxicoses.  

     There are several methods available for detection/estimation of aflatoxins in  the  

      feed/feed ingredients, the important ones are:

i. Thin layer chromatography (TLC) method

ii. High performance liquid chromotography (HPLC)

iii. Mini-column chromatography

iv. Aflatoxinometer

v. Enzyme linked Immunosorbant Assay (ELISA)

vi. Selective Adsorbant Mini Column (SAM) technique

Among the above methods, HPLC, SAM & ELISA are the most reliable methods, But ELISA test is most practically relevant test in the field because it is simple, accurate, reasonably economical, quick and commercially available.

METHODS TO CONTROL FUNGAL GROWTH & AFLATOXINS:

Fungal growth in feed & feed ingredients can be curtailed by addition of antifungal compounds in addition to the other measures already mentioned.  Among the various antifungal compounds available most commonly salts of acetic acid, Propionic acid,  Formic acid, Benzoic acid and Gention violet are used to prevent the growth of fungi.

Aflatoxins can not be completely eliminated but one has to minimise the levels so that it won't lead to economic losses.

Among the various detoxification procedures described, the following are the ones with practical applications:

a. Exposure to sunlight.

b. Use of toxin adsorbents - Hydrated sodium calcium aluminosilicate (HSCAS)

c. Dilution technique i.e. mix with good quality feed to bring down the level of aflatoxin within the permissible level.

d. Ammoniation

e. Dietary modification

f. Increasing protein/methionine, selenium content of feed

g. Increasing vitamins A, D, E, K and B-complex

h. Use of liver tonics

Among the various methods suggested, the use of blend/s of mold inhibitors and /or toxin binders appears to be the most common, economically and practically viable method.

Following are the practical tips for selection of toxin binder cum mold inhibitors to detoxify and curtail fungal growth.

1.  It must contain salts of Organic acids which:

a.   have brand spectrum of antimicrobial action

b.   are non corrosive

c.    have high diffusability and high dissociation factor

d.   Low volatality

e.   Protects the valuable nutrients in food

2.  It must contain treated Zeolites which:

a. ensures ample binding sites because of special physio-chemical treatment. 

b. stable complex with Mycotoxins at various pH of gut so that the bound toxins are not 

    released during passage through GI tract

3.  Optimal dosage:

     Optimal dosage of toxin binder (Zeolite) is most important that ensures particle to particle contact between the spread out mycotoxins with Zeolites in feed and in the intestine ensuring proper detoxification.

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Role of UTPP-5 in improving immunity:

INVITRO BINDING ABILITY OF UTPP-5:

Mycotoxicoses:

Mycotoxicoses is the intoxication that results in animals from the consumption of feedstuffs contaminated by one or more toxins of fungal origin.

Aflatoxin:

Aflatoxin is perhaps the most prevalent and most toxic of all mycotoxins commonly encountered in feedstuffs apt to be consumed by poultry.  The primary producers of the Aflatoxin are Aspergillus flavus and A. parasiticus.  Aflatoxin is produced readily in groundnuts, corn, cottonseed, feed stuffs derived from these primary commodities and a variety of other cereal grains and oilseeds.  Relatively warm and moist environments favour the production of aflatoxin in feedstuffs.  In recent years, aflatoxin contamination of feedstuffs has been especially  severe.  Drought, insect damage of developing plant structures, improper fertilization of crops and delayed harvest time have been shown to increase the incidence of aflatoxin contamination.  Substandard storage conditions of grain, improperly adjusted feed manufacturing equipment and storage conditions of grain, improperly adjusted feed manufacturing equipment and storage facilities for feed will also promote the growth of mold and lead to mycotoxin formulation.

Signs:

The signs of aflatoxicosis in poultry are non specific.  Impaired growth rates and feed conversion, increased mortality from infectious diseases and signs resembling nutritional disorders are typical.  Loss of  pigmentation and passage of undigested feed particles have been noted.  Young poultry are much more susceptible to aflatoxicosis than are mature animals.  Turkeys and ducks approximately 10% more susceptible to aflatoxin than are chickens of similar ages.

Lesions:

Aflatoxin produces a variety of clinical lesions in poultry.  Among these that are evident in acute outbreaks, or outbreaks characterized by chronic low level exposure to aflatoxin, are an increase in the size of the liver, kidneys and spleen, with the liver becoming friable, pale in  colour and extremely fatty with increasing severity of the outbreak.  Lymphoid tissue, including the bursa of Fabricius and thymus glands, undergo astrophy.  The gall bladder is usually enlarged and filled with bile that appears dilute.  

An increased susceptibility to bruising, resulting from increased capillary fragility, is often observed.  This effect is manifested by an increased incidence of Petechial haemorrhages of the musculature of young animals.

Although mature layers are more resistant to aflatoxin than are young chicks, mature birds exhibit similar changes in the internal viscera.   Decreased egg production and diminished interior and exterior egg quality is typical.  In breeders, the female appears to be more severely affected by aflatoxin than that of the male.  Increased embryonic mortality, decreased hatchability and an increased incidence of malformed embryos will be evident.  These effects occur from the transfer of aflatoxin  or its metabolites to the egg during the time of dietary intake of toxin. Within 7 days after the cessation of aflatoxin feeding, marked improvement in hatchability can be observed.