Mycotoxicosis in Poultry

Mycotoxicosis in Poultry

Introduction

·         A mycotoxicosis is a disease caused by a natural toxin produced by a fungus.

·         In poultry, this usually results when toxin-producing fungi grow in grain and feed.

·         Hundreds of mycotoxins have been identified, and many are pathogenic.

Major mycotoxins and its etiology

Fungus	Mycotoxin
Aspergillus species	Aflatoxin (B1, B2, G1, G2) Ochratoxin A Patulin
Fusarium species	Fumonisin Zearalenone Trichothecene (T2 Toxin, Deoxynivalenol (DON or Vomitoxin), Diacetoxyscirpenol (DAS)
Penicillium species	Ochratoxin A Patulin
Claviceps  species	Ergot alkaloids

Mycotoxcosis	Cause	Clinical signs	Organs affected	Gross pathology
Aflatoxicosis	Aspergillus flavus,  A. parasiticus	§ General unthriftiness § High morbidity and mortality.	§ Liver § Lymphoid organs § Hematopoeitc functions	§ Reddened due to necrosis and congestion or yellow due to lipid accumulation. § Hemorrhages may occur in liver and other tissues. § In chronic aflatoxicosis, the liver becomes yellow to gray and atrophied. § Ascites
Fusariotoxicosis	F. verticillioides  F. verticillioides  F. graminearum	§ Feed refusal, § Drop in egg production § Cynosis in comb and wattles in layers.	§ Oral mucosa § GI tract § Lymphoid organs	§ Necrosis and ulceration of the oral mucosa § Reddening of the GI mucosa § Diarrhoea § Mottling of the liver § Atrophy of the spleen and Bursa. § Lesions in proventriculus, and gizzard
Ochratoxicosis	Aspergillus ochraceus  Penicillium viridicatum	§ Depression § Huddling § Hypothermia § Diarrhoea § Rapid weight loss	§ Kidney § Liver § Lymphoid organs § Bone marrow	§ Damage of kidney § Fatty liver § Atrophy of the spleen and Bursa § Pale bone marrow § Ascites
Ergotism	Claviceps species	§ Discolored toe in chicks § Atropied comb, wattles in adults § Vesicles and ulcers develop on the shanks of the legs and on the tops and sides of the toes	§ Nervous system

Mycotoxin decontamination methods

A)   Physical methods

Antimycotic agents:

Antimycotic agents like sorbic acid and sorbate; propionic acid and propionate, benzoic acid, benzoates and parabens; and acetic acid and its derivatives are the chemicals that prevent mould growth and interfere with mycotoxin production.

Irradiation:

Gamma or electronic irradiation is highly effective for destroying the fungal spores. Fluorescent or ultraviolet (UV) rays decompose aflatoxins and ochratoxins.

Mechanical separation:

Toxin levels decrease as clean product is physically separated from contaminated grains.

B)   Chemical detoxification

Ammoniation:

Treatment with aqueous and gaseous ammonia or ammonium hydroxide, with or without heat and pressure to destroy the mycotoxin in contaminated food and feed is currently the best and effective method. Ammoniation not only detoxified several mycotoxins (85-100% reduction), but also inhibited mould growth.

Sodium hydroxide:

Warming of grain to 1050C in the presence of 0.5% sodium hydroxide detoxified various mycotoxins in the feed.

C)   Biological Inactivation

1.    Mycotoxin-binding agents:

Numerous agents like, activated carbons (charcoal), bentonites, clay, hydrated sodium calcium alumino silicate, and zeolite, have currently been used to counteract the mycotoxicosis in poultry and its carry over effect through meat and eggs.  These sorbents are nutritionally inert and reduce the bioavailability of various mycotoxins by absorption on their surface in intestinal tract.

Activated charcoal: It has high ability of binding with several mycotoxins. The adsorption property of AC was found effective against aflatoxin B1 and ochratoxin A up to 95% and 91%, respectively. Charcoal at 2% level had shown beneficial effects.

Bentonites: Bentonites (hydrated aluminium silicate) are sorbents with layered (lamellar) crystalline microstructure and variable composition. Their absorption property mainly depends on the interchangeable cations (Na+ , K+ , Ca++ and Mg++) present in the layers. Sodium bentonite is more effective than calcium bentonite. Bentonite could bind aflatoxin to the extent of 66% while it was of little use in adsorbing OTA.

Hydrated sodium calcium alumino silicate (HSCAS): Molecular surface of HSCAS gets saturated with water and attracts the polar structure of various mycotoxins. In young broiler chicks, HSCAS (0.5%) was effective at reducing the toxicity of aflatoxin  as well as combined toxicity with OTA. However, its protective properties are very low towards OTA, zearelenone and nil towards trichothecenes.

2. Microbiological binding agents: Mannan oligosaccharide (MOS) extracted from the cell wall of Saccharomyces cerevisiae has shown broad-spectrum efficacy against most of the mycotoxins. Saccharomyces cerevisiae was found to have beneficial effect in poultry during mycotoxicosis and MOS was believed to be the responsible factor and showed significant binding over zearelenone, T2 toxin and moderate binding over OTA (25.5%), during in vitro studies

D)   Antioxidant substances

The protective properties of antioxidants are probably due to their ability to act as superoxide anion scavengers, thereby protecting cell membranes from the mycotoxin induced damage.

Ascorbic acid (Vitamin C):

The addition of vitamin C to the diet containing OTA, partially protected laying hens against the toxic effect. The OTA induced reduction in feed intake was counteracted at 250C by vitamin supplementation.

Phenolic compounds:

The phenolic antioxidants, gallic acid, vanillic acid, protocatechuic acid, 4- hydroxybenzoic acid, catechin, caffeic acid, and chlorogenic acid were found to be effective against the fungal growth of ochratoxigenic Aspergilli and the OTA production.

Vitamin A:

Vitamin A possesses the antioxidant properties against the mycotoxin-induced damage. Carotenoids, mainly carotenes and xanthophylls present in carrots, palm oil and maize, not only possessed the antioxidant property but also had antimutagenic and anticarcinogenic properties and reduced the toxicities of OTA.

Vitamin E/Selenium:

Supplementary vitamin E administration to chickens partially counteracts the formation of lipid peroxides due to single and combined exposure to OTA and T2 toxin. Higher vitamin E intake partially ameliorated oxidative stress caused by OTA. It is known that reduced vitamin E (alpha tocopherol radicals) can be regenerated following single electron reduction by ascorbic acid. Vitamin C should, therefore, enhance the biological efficacy of vitamin E especially under stress condition. Vitamin E and selenium are involved in the formation of glutathione peroxidase, a compound vital in the cellular detoxification mechanism.

E)   Food components and additives

Numerous food components, ingredients, or additives with or without antioxidant properties have been found to have ameliorative properties against mycotoxicosis.

Aspartame:

Aspartame (L- aspartyl- L- phenylalanine methyl ester), a structural analogue of both OTA and phenylalanine, has been shown to have protective effect against OTA induced cytotoxicity in animals. Aspartame prevents typical cytotoxic effects of OTA including inhibition of protein synthesis, lipid peroxidation and leakage of certain enzymes, such as lactate dehydrogenase, gamma glutamyl transferase and alkaline phosphatase.

Crude proteins:

Raising the protein levels of diet from 14-18% to 22-26% counteracted the OTA effects.

Dietary lipids:

Inclusion of cottonseed oil at 2, 6, or 16% level into semi-purified diets containing 10 ppm aflatoxin, not only improved the body weight, but the mortality was also significantly reduced. The higher levels of dietary fat reduced mortality and in some instances, improved the body weights. Lipids exerted their effects in part by interfering with absorption of the aflatoxin. Supplementation with olive oil and safflower oil, both sources of unsaturated fatty acids, also improved body weight which suggested that diets containing higher levels of linoleic acid supported better feed conversion and lower mortality in chicks fed diets with aflatoxin.

L-Methionine:

It has been reported to have a protective effect against many oxidant drugs. It plays an important role in preserving the structure of cell membrane and in modulating the antimicrobial activity of polymorphonuclear leucocytes in periodontal disease as well as behaving as a chemotherapeutic agent in hepatitis treatment.

Treatment

·         The most effective treatment is removal of the source of toxins.

·         Addition of antifungal feed preservatives is also helpful.

·         Increasing protein level in the feed until mortality reduces may also be beneficial.

·         Administration of soluble vitamins and selenium. (Vit. A, D, E, K, C)