Toxin management: A key to profitable farming
Toxin word is derived from Latin word "Toxicum" means poison. Any small molecule, peptide or protein which has potential to alter the normal metabolism of host cells with deleterious effect comes under toxin. Animal feeds provides all the vital nutrients to animals so that their body functions well and their health remains in great condition. A healthy not only keeps them away from diseases but also enhances the quality of the produce derived from them. But, animal feed also has the potential to contain a wide range of contaminants including biological, chemical (including radiological), or physical. Contaminants maybe introduced into animal food from either natural sources (Mycotoxins) or potentially introduced during the manufacturing process. These toxic compounds present may exert antinutritional effects, reduce reproductive performance, decreases body weight, causes mortality and adversely affect health of farm animals
Environmental pollutants: Sources of toxins in animal feed
Animal feeds are regularly subject to contamination from anthropogenic and natural sources, including environmental pollution, distribution of heavy metals, radionuclides, mycotoxins, plant toxins, drug residues and microbial pathogens in cereals, complete feeds and forages. Feeds contain a variety of substances as co-contaminants and there are regional differences in the nature of the compounds involved. Pesticides like organochlorine, organophosphate and pyrethroid compounds, which are sprayed in the standing crops due to their residual activity causes toxicity. A recent survey indicated that 21 percent of feeds in the United Kingdom contain pesticide residues. Rodenticides applied to poultry houses as rodent baits however, careless application can result in their consumption by poultry, causes acute toxic effects. Contamination of feeds and herbage with Cadmium may occur as a result of applying certain types of fertilizers to crops and pastures. On the other hand, Lead contamination arises from industrial pollution, while Mercury in feeds arises from the use of fishmeal. Pirimiphos-methyl, an insecticide used in grain stores, was found with the highest frequency in farms.
Animal feeds may also contain endogenous toxins arising principally from specific primary and secondary substances produced by fodder plants and these toxic components have the potential to precipitate adverse effects on the productivity of farm animals and birds. Plant toxins may be divided into a heat-labile group, comprising lectins, proteinase inhibitors and cyanogens, which are sensitive to standard processing temperatures, and a heat-stable group including, among many others, antigenic proteins, condensed tannins, quinolizidine alkaloids, glucosinolates, gossypol, saponins, mimosine and phyto-oestrogens. Lectins are proteins capable of damaging the intestinal mucosa, thus reduces nutrient absorption and impairs immune function. Trypsin inhibitors in soyabean reduces protein digestion and causes endogenous loss of amino acids. Glucosinolates causes organ damage, goitrogenic effects or reduced feed intake, particularly in non-ruminant animals. Gossypol from cotton seed cake causes organ damage, cardiac failure and death. Therefore, these antinutritional factors when exceeds their acceptable inclusion rate causes disease condition and deteriorate health and production.
Endotoxins: A Hidden threat in feed
Refers specifically to the lipopolysaccharide (LPS) located in the outer membrane of Gram-negative bacteria. LPS are released into the environment when the bacteria multiply or when their cell membranes rupture through bacterial lysis and thus causes inflammatory immune response in the animal which comes at the expense of the production performance. Gastrointestinal tract is the main target site, where they can be transferred from the lumen into the bloodstream, causing endotoxemia. The permeability of the gut is tightly controlled by enterocytes which are connected by tight junction proteins, this keeps endotoxins on the luminal side. But when dysbiosis occurs, several external factors (Heat stress, sudden changes in diet, pathogen, low ruminal pH and high osmolality etc) increases gut permeability and excessive triggering of the immune system. This promotes leakage of endotoxins into the bloodstream, can result in septic shock and even death. The translocation of endotoxins into the blood steam can also take place across the rumen epithelium, which is a multi-layer structure and is covered by keratinised cells. A single Escherichia coli contains about 2 million Lipopolysaccharide molecules per cell. Since faecal contamination of feeds is widespread on farms, it is important route for exposure of animals or birds to bacterial toxins. The potential for exposure to bacteria also exists when poultry litters are fed to cattle. Clostridium botulinum bacteria produce several exotoxins that are among the most potent toxins known. Bone meal can be a possible source of botulism. Endotoxins has cosmopolitan distribution: in the air, the water, soil and in the gastrointestinal tract of animals. Protecting all livestock from their toxic effects should be a priority for everyone from feed to farm. Like providing the products which are adequately heat processed, the risks of contamination with E. coli, Salmonella spp. and Campylobacter spp. are likely to be controlled.
Mycotoxins are cosmopolitan menace to farmers
Mycotoxins are low molecular weight secondary metabolites produced by certain strains of filamentous fungi such as Aspergillus, Penicillium and Fusarium, which invade crops in the field and may grow on foods during storage under favourable conditions of temperature and humidity. Mycotoxin producing fungi are divided into two groups:
a. Field fungi: Field fungi invade the grains while the crop is in the field (occurring prior to harvest) and usually require high moisture conditions. e.g. Fusarium and Alternaria spp.
b. Storage fungi: Storage fungi invade the grains during storage and require less moisture than field fungi, and do not present any serious problem before harvest. e.g. Aspergillus and Penicillium spp.
Mycotoxin producing fungi are mostly ubiquitous in nature. The mould infestation of the feedstuffs has a great negative impact on the quality of feed. The physical signs of mould occurrence in animal feeds are dustiness, poor flow out of grain bins, feed refusal by animals, mouldy and musty smell, and darkening of grain.
Factors affecting development of fungi and mycotoxin production are:
a) Physical factors: Humidity, temperature, microflora zones and physical integrity of the grains
b) Chemical factors: pH, composition of the substrate and mineral nutrients
c) Biological factors: Presence of insects and specific strains
Aflatoxins are highly toxic compounds. The liver is the main organ affected, followed by the kidneys. They cause hepatic changes leading to serious liver damage characterized by haemorrhages, cirrhosis and fatty degeneration of the liver. However, pancreas, gall bladder, lung and gut may also be affected. Aflatoxins are absorbed from the gut and are transported to the liver where they are metabolized. Among the naturally occurring aflatoxins, AFB1 is the most acutely toxic followed by AFG1, AFB2 and AFG2. Adverse effects on the gastro-intestinal tract are probably the major cause of economic losses resulting from trichothecene. T-2 toxin can cause caustic injury to the mucosa, destroying cells on the tips of villi, and affect rapidly dividing crypt epithelium. Zearalenone affects the reproductive system of pigs. This toxin is responsible for vulvovaginitis and estrogenic syndrome that affects any stage of reproductively active swine. Zearalenone is found to be relatively stable in heat conditions. While the mold can withstand high heat conditions, growth most efficiently in moist and cooler conditions. Co-contamination of mycotoxins is major risk as synergistic interactions exaggerate toxicity symptoms. A per recent survey conducted by renowned Indian company it shows that from the total samples analysed, 86% samples were contaminated with more than one mycotoxin and 24% samples were contaminated with more than four different mycotoxins and corn gluten meal is highly contaminated with all mycotoxins.
Management of toxins
• Good manufacturing practices and hazard analysis critical control points should be applied
• Proper drying and storage of grains can avoid occurence of mycotoxins. Exposure to sunlight for 12-14 hrs degrades aflatoxin up to 70-90%
• Efficient detoxification strategies should be practiced
• Autocalving and pelleting can be a good practice. Pelleting causes destruction of heat labile toxin factors. It also maintains the integrity of the gastrointestinal tract and the heat treatment associated with pelleting improves feed digestibility by deactivating anti-nutritional factors
• Chemical agents like alkali (Calcium hydroxide, Ammonia) and acids (Benzoic acid, Copper sulphate@ 0.04-0.05%) is effective in treatment of fungal contamination
• Use of adsorbants/binders (Inorganic and organic toxin binders)
Role of Toxin binder
Refers to a substance added to feed in minute quantities that is able to neutralize or immobilize harmful chemicals, mycotoxins or endotoxins (lipopolysaccharides) within a gastrointestinal tract, thus avoiding negative consequences. They prevent toxins from entering the blood stream, where they can cause serious harm to your animals. They help by reducing bioavailability of toxins in the diet and prevent them from being absorbed through the gut and entering the blood circulation. They improve overall animal health and also reduce risk of human exposure.
Characteristics of ideal toxin binders
• Ability to bind wide range of mycotoxins
• Low effective inclusion rate
• Rapid & uniform dispersion during mixing
• Heat stable
• No affinity for other nutrients
• pH stable
• Aluminosilicates are clay minerals composed of aluminium, silitium, and oxygen, plus countercations. Natural soil minerals (Zeolite and bentonite) are crystalline alumino-silicates characterized by their ability to exchange cations without major changes in structure. Natural clays can adsorb toxic products of digestion and decrease the accumulation of toxic substance, thus decreasing the incidence of internal disorders. Natural soil minerals may stimulate the lining of the intestinal tract that increases the production of antibodies, which could then inhibit the onset of enteritis. HSCAS is the most binder which was studied very carefully on many species such as poultry, swine and cattle.
• Activated charcoal is a universal toxin binder. It is a general adsorptive material with a large surface area and excellent adsorptive capacity and recommended for various digestive toxicities. Many toxins are positively charged, and a binder that is negatively charged like charcoal will be attracted to them, and able to adsorb many of them. The Activated charcoal and the toxin are then excreted in the feces if it is part of food ingestion, or if it is cycling through the enterohepatic circulation with the bile. Activated charcoal is not absorbed by the body. Therefore, if it binds a toxin in the intestinal tract, it and the toxin end up leaving the body.
• Organic acids controls and prevents fungal growth by lowering pH of feed. They also enhance digestibility of nutrients by lowering pH of gut. This aids digestibility of proteins and thus increases availability of amino acids.
• Cinnamaldehyde inactivates S.enteridis, C.jejuni& reduces colonization,while Carvacrol has action against C.perfringens & E.coli.They down-regulate toxin producting genes, modulates transcriptional repressor and modifies bacterial membranes, thus arrest bacterial multiplication.
• Yeast cell walls are potential mycotoxin binders, besides having nutritional value. Using only yeast cell walls instead of whole cells, the adsorption of mycotoxins can be enhanced. The beta-d-glucan fraction of the yeast cell wall is directly involved in the binding process with Fusariummycotoxins as zearalenone, and the structural organization of beta-d-glucan modulates the binding strength.It appears that carbohydrate components are common sites for binding, with different toxins having different binding sites. Microbial cell walls can be used to alleviate the harmful effects of mycotoxins in contaminated feeds. Adsorbents derived from cell wall of the yeast Saccharomyces cerevisiaeand lactic acid bacteria have shown to bind Fusarium toxins and help reduce the toxic effects in animals. Complex carbohydrates in bacterium and yeast cell walls such as β-glucans and mannans have been demonstrated to adsorb mycotoxins (Zearalenone, Ochratoxin A (OTA), a toxic secondary fungal metabolite that widely takes place in various kinds of foodstuffs and feeds.
• Herbs like Azadirachta indica has potent antifungal and antibacterial action that fights with the endotoxins producing bacteria. It is effective against a wide spectrum of insects, fungi and viruses, which reveals its great potential as a possible biological control of fungi and mycotoxins
• Humic acid acts as natural chelator of toxin or heavy metals & push them out of the body. The supplementation of Humic acid also enhances the humoral immunity by counteracting the aflatoxin contamination.
One can use combinations of absorbants, toxic binders, organic acids and herbal extract to enhance toxin binding. Nutricare offers combination of HSCAS, Organic acid, Activated charcoal, MOS, Organic acid fortified with herbal extracts in form of TOX-00, which is natural toxin binder and selectively binds aflatoxins, B1, B2, G1 & G2 and gives complete protection from mycotoxin related damages. It avoids binding of Vitamins, trace minerals and avoids caking of feed. Inhibits growth of bacteria by decreasing pH & neutralises major toxins by adsorption.
Tox-00 can be used in poultry feed@ 500g per ton of feed and in swine feed@ 1kg per ton of feed.
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Article made possible through the contribution of Dr. Vandana Sharma, Dr. Saurabh Agarwal and Nutricare