AFLATOXICOSIS IN POULTRY- Clinical Sign, Impacts & Control
Dr.Deepak Prasad Sinha,
Technical Manager,Venkys, Patna
Aflatoxicosis is caused by the ingestion of one of the classes of toxins found in certain fungi called aflatoxins, which are produced by Aspergillus flavus, A. parasiticus, and other strains of Aspergillus. The 4 aflatoxins of concern are B1, B2, G1, and G2. However, B1 is the most predominant and toxic to humans and animals. Aflatoxin contamination is typically found in grains and tree nuts, peanuts and peanut products, corn and corn products, cottonseed oil, and milk. Crops can become contaminated with aflatoxins while growing in the field, during harvesting, transportation, mixing, or during storage. Government Regulations for Aflatoxins The FDA and the EU regulate the amount of aflatoxins present in human food, animal feed, and animal feed ingredients. For chick starter and grower feeds, corn, and peanut products, excluding cottonseed meal: Must contain less than 20 ppb For laying hen feed and other mature poultry: Must contain less than 100 ppb For cottonseed meal intended for all types and ages of poultry: Must contain less than 300 ppb.
Aflatoxins are one of the key challenges faced by poultry farmers as well as by Poultry Feed manufacturer in India as it leads to serious economic losses. In our country having tropical climate with hot and humid condition coupled with poor harvesting of crops during monsoon season, inadequate drying and storage facilities make feed stuff susceptible to fungal contamination resulting in greater economic losses to poultry industry through Mycotoxicosis. In addition to these there are improper management practices which are being followed at more than 60 percent poultry farms in India which further increases the risk of mycotoxins to very high level.
Mycotoxicosis is the condition associated with fungal contamination of feeds or feed ingredients. Among mycotoxins, aflatoxins are predominant and are one of the major fungal toxins which are responsible for potential problem in Poultry feeds. Aflatoxins are produced from fungi of the genus Aspergillus and major forms of aflatoxins include B1, B2, G1 and G2 with B1 being the most dangerous and common active toxin. It’s just not about Poultry but aflatoxins affect both human as well as animals. If we go into past the first time it was discovered in 1961 in Britain when more than 100,000 turkeys and many farm animals died from a mysterious disease. When cause of this disease was investigated it was found to be aflatoxins in the feed. Sources & Guidelines of Aflatoxins in Poultry diet Aflatoxins are found almost in every grains used in Poultry Industry either its Maize, Bajra or wheat. The only difference lies is in the level which mostly found very high in Maize. More than this cereal grains, soybean products, oil cakes (from groundnuts, cottonseed, sunflower, palm, and copra), and fishmeal all are having some amount of Aflatoxins. Brewers grains (a by-product from cereal-based alcoholic drinks) Corn Gluten and rice gluten all can have high levels of aflatoxins. In general, livestock in intensive systems e.g. poultry are at higher risk of dietary exposure than animals in extensive systems because in intensive system animals cannot do selective feeding or can depend on the feed which is being provided to them. Throughout world poultry birds are kept mostly in intensive systems hence aflatoxins are likely to be an increasing problem. There are strict guidelines regarding the level of Aflatoxin throughout world, especially in countries where regulation for aflatoxins in animal feeds exists, the total permissible aflatoxins levels in animal feeds range from 0 to 50 parts per billion (ppb) with an average of 20 ppb. In India as per the BIS standards the level of Aflatoxins should not be higher than 50 ppb in poultry feed but samples having levels above 50 ppb and contamination of 100 to 500 ppb are not uncommon and being reported time to time by various researchers as well as by various laboratories.
Susceptible Poultry —
Depend on the sensitivity to aflatoxins livestock species are graded as below -Rabbits>Ducks>Turkeys>Chicken>Fish>Swine>Cattle>Sheep.
This grading suggests that Poultry has very high degree of susceptibility to aflatoxins as compare to other farm animals like Cattle and Fish. The effects of aflatoxins on Poultry depend on various factors like genetic (species and breed strain), physiological (age, nutrition, and stress) and environmental (climatic and farm management). Chicks at brooding stage are susceptible to even low levels of aflatoxins while and young and fast-growing birds are more affected than adults. Broiler birds are much more sensitive and susceptible than a well grown layer birds. Male birds are more susceptible than female due to higher growth rate.
Clinical signs——-
the most economically significant effects in growing birds are decreased growth rate and poor feed conversion because metabolites of aflatoxins bind to DNA and RNA of the cells and hence reduce protein synthesis.
immunosuppressive effect due to decrease cell mediated immunity and to lesser extent humoraI immunity leading to vaccination failure and decrease resistance to infectious disease.
passage of undigested food in the dropping.
anemia of the infected birds due to decrease food intake and hence occur failure of normal pigmentation and decrease pcv.
decrease egg production in layers quantitatively and qualitatively also in breeders decrease hatchability due to embryonic mortality and may fertility due to decrease testicular weight and hence decrease semen volume (sperm counts).
may lamness , ataxia , convulsions and opisthotonus preceded death. Mortality depends on amount and type of toxin consumed species of birds and age.
Permissible levels of aflatoxins——
Maximum permitted levels of aflatoxins in feed 20 ppb (20 ug / kg of food or 20 mg /ton).
1 00�200mg/ton�+ low toxicity,over2 00mg/ton .high toxicity.
> 1000 ppb = 1000 mg / ton = 1 gm / ton is harmful for broilers and layers.
>10.000 ppb = 10.000mg / ton 10gm / ton may be lethal.
Post mortem findings—-
lesions depend on the species and age of the host and the dose of the toxin.
aflatoxins have hepatotoxic effect so the liver is swollen , pale or yellow due to precipitation of fat as a result of hyperplasia of bile ducts epithelium due to inflammation of these ducts , friable and has hemorrhages , gallbladder enlarged and in the late stage fibrosis of the liver may occur.
enlargement of the kidneys , spleen and pancreas.
atrophy of bursa fabricci , thymus gland , spleen and testes.
hemorrhages present under the skin, on muscles and on the internal organs due to fragility of blood vessels and decrease clotting factor synthesis.
in chronic stage ascites and hydropericardium developed.
Government Regulations for Aflatoxins
The FDA and the EU regulate the amount of aflatoxins present in human food, animal feed, and animal feed ingredients. For chick starter and grower feeds, corn, and peanut products, excluding cottonseed meal:
Must contain less than 20 ppb For laying hen feed and other mature poultry: Must contain less than 100 ppb For cottonseed meal intended for all types and ages of poultry:
Must contain less than 300 ppb The adverse effect of aflatoxins depends on the age, species, nutritional status of birds as well as the dose and length of time it was consumed. Aflatoxicosis refers to poisoning from ingestion of aflatoxins in contaminated food or feed. Both acute and chronic aflatoxicosis can occur, however the chronic form is the most prevalent. Chronic aflatoxicosis occurs as a result of prolonged intake of low levels of aflatoxins in the chickens’ diet.
Resulting adverse affects include:
Immunosuppression:
Increases susceptibility to secondary infection by opportunistic pathogens.
Reduced vaccine effectiveness:
Decreases resistance against viral pathogens, increasing the risk of acquiring the disease they are getting vaccinated against.
Gastrointestinal tract damage:
Causes erosion and roughening of the gizzard lining, resulting in decreased absorption of nutrients, stunted growth, nutrient-deficient related syndromes, and lowered feed conversion. Liver damage: The primary site of toxicity due to aflatoxins is the liver. Exposure causes hepatic lesions and enlargement of the liver as well as fatty liver.
Production losses:
Decreases egg production and egg quality in laying hens and hatchable eggs in breeding chickens.
Effects of aflatoxins on Poultry health and production ——-
There are two types of toxicity happened due to aflatoxins in Poultry
1. Acute Toxicity
2. Chronic toxicity
The acute toxicity of aflatoxins in poultry varies from species to species as well governed by the age, sex and strain of the bird and its condition and generally leads to very high mortality in limited period. A variety of chronic effects has been reported for aflatoxins when fed to poultry. Chronic aflatoxicosis probably has greater economic impacts than acute disease. Numerous studies show a worsening in feed conversion ratios, a decrease in average daily gain, a decrease in body weight, lower pigmentation, less processing yield, lower egg production, effected male and female fertility, higher leg problems and lower hatchability in birds experimentally fed aflatoxins. Diets containing aflatoxins, when fed to poultry, increase the risk of attack by bacteria and viruses. The immune status of the bird is effected significantly as a result of continuous exposure of aflatoxins and organs such as Liver, Kidney, Bursa, thymus and lymph nodes are the one having maximum damage. Aflatoxins have been reported to affect the digestion of number of essential components of the poultry diet, such as coccidiostats, vitamins and amino acids. This can have a disastrous effect on poultry health and production as it make poultry birds susceptible to various production diseases such as Coccidiosis, Enteritis etc.
Clinical signs of aflatoxins toxicity——
include anorexia, specific visceral haemorrhage, embryo toxicity and very high susceptibility to various environmental and microbial stressors. On analyzing through histopathology the most common findings or symptoms include fatty liver, necrosis of liver and hyperplasia of bile duct. Aflatoxins have very high effects on metabolism in poultry. The activity of various enzymes required for digestion of carbohydrate, protein, fat and nucleic acid has been decreased due to aflatoxins.
Various studies have also found out that level of total protein, cholesterol and blood urea nitrogen get decreased due to effect of aflatoxins in Poultry.
Aflatoxins also have interaction with vitamin D metabolism which leads to decrease bone strength and various leg disorders. The leg disorders may be also because of extra interaction of aflatoxins with other mineral like phosphorous, Copper and Iron. Aflatoxins adversely affect cellular as well as humeral immunity. A slight lower level of aflatoxins in diet affect cellular immunity but at higher level the immunoglobulin production and response to antibodies get suppressed. Many disease outbreaks, vaccination failures and poor titre of antibodies happen because of continues exposure of aflatoxins.
Impacts of aflatoxins on meat & egg quality——
A very minute level of aflatoxins and their metabolites may also carry over into the edible tissue of poultry birds. Poultry feed contaminated at the level of 3,000 ppb may result in levels of 3 ppb in poultry meat same way aflatoxins may be carried over from feed to eggs.
Aflatoxins accumulation as residue into poultry meat is much lower than transfer into ruminant milk. In case of eggs also the level of transfer is quite lower. So overall the impact of aflatoxins is more on health & production rather than on the meat or egg quality in poultry.
Control of aflatoxins in poultry feed ——-
A practical aflatoxins control completed in two stages i.e. preventing the fungal growth as well as toxin production and secondly decontamination of existing aflatoxins in poultry feed. Several works as well strategies has been proposed by researchers such as plant breeding in such a way which can reduce the mould growth. Simultaneously improving harvesting and storage practices which can minimise contamination procedure hence reduce in aflatoxins production. For the toxin already present in the feed the most effective method for control is by addition of adsorbents which can prevent the toxin absorption from intestine. The addition of binder such as zeolite clays and aluminosilicates is very effective in reducing aflatoxins related toxicity. There are many clay base products marketed by various companies present in market having good efficacy against aflatoxins. One method of reducing moderate levels of aflatoxins contamination is by mixing good quality grain in aflatoxins contaminated feed, as this will help in reducing the overall level of aflatoxins in feed. This method is being applied by farmers at various level to control Mortality of birds as it helps in slowing down the metabolism of bird by lower density nutrition and secondly dilution of aflatoxins. Some Nutritional Modifications in feed are also very much useful for protection against aflatoxins which includes higher supplementation of vitamins, methionine and selenium. There are few chemical such as sodium bisulphite, ammonia and peroxide acids tested for detoxification but found impractical especially due to safety and palatability issue.
Differential diagnosis
Aflatoxicosis must be differentiated
From: Disease causing decrease growth rate, decrease egg production, immunosuppressive effect, hemorrhages and enlargement of organs especially liver.
Prevention
shipments falling outside acceptable levels should be rejected. also grains of high % of destruction.
antifungals as organic acids ,copper sulphate , gentin violet, thiabendazde, ammonium hydroxide , must be added routinely to the feeds to prevent fungal growth in storage pins or finished feeds , other method of prevention include ozone treatment of grain.
feed must be stored in well ventilated place, far away from floor and walls to avoid exess moisture (must be less than 12 %) and prefer to prepared fresh ( store time must not exceed than 14 days), also well ventilation of poultry house to prevent fungal growth.
litter must stored in well ventilated places and in poultry house must preserved it dry and wet places around watering troughs must be replaced by dry one to prevent fungal growth.
poultry farms should have two bins per house to allow rotation and cleaning.
thorough cleaning and disinfections of grain mills, feed store, bins, feeding troughs and pen after each batch with antifungal substances as formalin 2-3 % or copper sulphate.
you can analyse (check ) prepared feed to sure its freedom from mycotoxin.
you can use pelleted feed because during their manufacturing process cause destruction of fungal spores , also irridation , fumigation of feeds may prevent mold growth regular inspection of feed bins.
N.B.:-
Spices oils and extracts are effective as mould inhibitor.
Copper sulphate is a poor mould inhibitor for poultry feeds.
Control
Contaminated feed must be stopped (feed stock and feeds in feeding troughs) and replaced by another feed free from aflatoxin, birds recover fiorn most mycotoxins soon after replacing contaminated food by uncontaminated one.
Treat the birds with some antitoxic substances that having the ability to bind with aflatoxin and prevent its absorption from the gastrointestinal tract , some of these substances can be used in the feed and the other in water as sodium calcium aluminosilicates or bentonites or zeolites or clinoptilolites .fine particles size superactivated charcoal had marginal or no binding activity for aflatoxin or T -2 toxin.
Because some vits. For ex.vit E and C counteract the toxicity of T2 toxin or ochratoxin A. vitamins, trace elements especially selenium (protective by increasing the percentage of conjugated aflatoxin), protcins especially methionine and cysteine which counteract aflatoxin and lipids must be compensated by feed formulation.
Birds vaccinated during the clinical signs of aflatoxicosis must be revaccinated
Treat concurrent bacterial or parasitic infections.
Conclusion —–
Aflatoxins can seriously reduce poultry productivity. In our country there is no poultry feed which is totally free from aflatoxins. There are instances where poultry are fed highly contaminated grains considered unfit for human consumption and are thus at risk of acute toxicosis. But in most of cases its chronic aflatoxicosis which is probably a major cause of concern as it leads to economic loss especially to poultry farmers as some time difficult to diagnose. The adverse effects of aflatoxins on poultry are too high hence there is danger which is very clear and persistent. Very careful and strong steps needed to control this problem which occurs naturally. One small step especially in developing countries like India where there is shortage of feed ingredients like corn may be to use most aflatoxins-contaminated corn in livestock feed rather than in poultry as poultry are much more susceptible. Although there are still no established levels at which we can say that aflatoxins are safe for livestock, and these large animals can tolerate aflatoxins well. Overall we should have the usage of quality ingredients in poultry diet alongside use of some mold inhibitors & binders to control the growth of mould responsible for aflatoxins. Simultaneously the farm management plays a far greater role in controlling the overall losses due to aflatoxins so it’s mandatory for the poultry farmers to follow best management practices for rearing their flocks.
