Dairy Farming-डेयरी फ़ार्मिंग

USE OF TOXIN BINDERS IN CATTLE FEED

June 23, 2019

2870

Compiled & shared by-DR. RAJESH KUMAR SINGH, (LIVESTOCK & POULTRY CONSULTANT), JAMSHEDPUR, JHARKHAND,INDIA 9431309542, rajeshsinghvet@gmail.com

What are mycotoxin binders?——-

Mycotoxin binders or adsorbents are substances that bind to mycotoxins and prevent them from being absorbed through the gut and into the blood circulation. When other preventive measures against molds and mycotoxins have failed, the use of mycotoxin binders can be valuable. There also may be instances when feeds and feedstuffs cannot be checked for mycotoxins on a regular basis. Mycotoxin binders are routinely added in such cases as safety measures and as some form of assurance to customers. A variety of substances have the ability to bind mycotoxins. The most commonly used and most researched mycotoxin-binding agents are the aluminosilicates – clays and zeolites. These are natural adsorbents that include hydrated sodium calcium aluminosilicates (HSCAS), bentonite, and zeolite . Most of these products are efficient binders of aflatoxins. However, they have limited or no activity against other types of mycotoxins. Other substances with toxin-binding capability include cell-wall components of yeasts. Some studies have shown that the cell-wall fraction β-glucan of yeasts such as Saccharomyces cereviceae can be effective in binding a wide range of mycotoxins. Unlike clays, they can be added at low levels and are biodegradable.

Livestock feed toxin binders are a great way to reduce mycotoxicosis and improve livestock health and productivity. Aquaculture, deer, equine, household pets, poultry, ruminants, and swine rely on a consistent supply of nutrient-rich feed to achieve optimal health. Toxin binders added to animal feed provide an excellent source of nutrient and health security.

Over 500 different mycotoxins have been identifies to date and often feeds contain many different mycotoxins. We know that mycotoxins are “toxins” and their insidious effects on cattle are deleterious, many and manifold. Yet the problem of mycotoxins in feed has been largely ignored. The widespread nature of the problem and the long term effects on cattle health and performance have not been fully appreciated.

The word “mycotoxin” literally means “fungus-poison.” Mycotoxins are secondary metabolites produced by molds and fungi in fields and during storage of grains, feeds and forages. Mycotoxins are considered to be soil-borne pathogens. Not all molds and fungi will produce mycotoxins, however.

Toxin Binders for animal feeds

The addition of Toxin binders to contaminated diets has been considered the most promising dietary approach to reduce effects of Toxins. The theory is that the binder decontaminates mycotoxins in the feed by binding them strongly enough to prevent toxic interactions with the consuming animal and to prevent mycotoxin absorption across the digestive tract. Therefore, this approach is seen as prevention rather than therapy. Potential absorbent materials include activated carbon, aluminosilicates (clay, bentonite, montmorillonite, zeolite, phyllosilicates, etc.), complex indigestible carbohydrates (cellulose, polysaccharides in the cell walls of yeast and bacteria such as glucomannans, peptidoglycans, and others), and synthetic polymers such as cholestryamine and polyvinylpyrrolidone and derivatives.

Livestock enterprises faces the maximum loss is owed to the contamination of animal feed ingredients and compounded feeds by moulds and its toxic metabolites known as mycotoxin. Some of the primary toxigenic moulds and mycotoxins are indicated as following:

Mycotoxins—

1.Fusarium spp.———— Deoxynivalenol, Zearalenone, T-2 Toxin, Fumonisin, Moniliformin, Diacetoxyscirpenol, Fusaric acid, etc.

2. Aspergillus spp.———– Aflatoxin, Ochratoxin, Sterigmatocystin, Cyclopiazonoic acid, etc.

3. Penicillium spp.———– Ochratoxin, PR Toxin, Citrinin, Cyclopiazonic acid, etc.

Among these, the most important mycotoxins are the aflatoxins. The aflatoxins (AF), a class of mycotoxins produced by the common mould Aspergillus flavus Link and Aspergillus parasiticus Speare. Major forms of aflatoxin include B1, B2, G1, and G2, with aflatoxin B1 being the most common and biologically active component (1). All four have been detected as contaminants of crops before harvest, between harvesting and drying, during storage, and after processing and manufacturing .

The primary mechanisms through which mycotoxins affect animals are :

1. Reduction of feed intake
2. Reduced nutrition (reduced nutrient content of the feed, reduced nutrient absorption and altered nutrient metabolism)
3. Immunosuppression
4. Mutagenicity
5. Teratogenicity
6. Cellular death

Chronic exposure to the mycotoxins may significantly alter productivity, which can mean the difference between profit and loss to the livestock industry. Consequently, practical and effective methods to detoxify toxins-containing feedstuffs are in great demand. Various physical (grain cleaning/seperation, heating, irradiation), chemical (ammoniation, sodium bisulfite) and biological approaches (microbial, non-toxic strains) to counteract the mycotoxins problem have been reported but these methods have certain limitations like they are impractical, ineffective and potentially unsafe.

Certain adsorbents to contaminated diets can greatly reduce the bioavailability of toxins in the gastrointestinal tract . Some mycotoxin adsorbents are given below:

1) Silicate Products:

Phyllosilicates (silicate sheets): Clays [Montmorillonite, bentonite and Hydrated Sodium Calcium Aluminosilicate (HSCAS)].
Tectosilicate (silicate frameworks): Zeolites and Clinoptilolite.

2) Carbon Products:

Activated or superactivated charcoal.

3) Glucan products

4) Inorganic polymers:

Cholestyramine.
Polyvinylpyrrolidone (PVP).

Binder evaluations and concerns———-

Research with mycotoxin binders has been conducted for over 20 years, and yet products are still not approved for the marketplace. Mycotoxin binders have been evaluated using both in vitro and in vivo systems. In vitro evaluations have been useful as a screening method for potential binder products, providing an idea of binding affinity and capacity. In vitro data should not be used to make decisions about products to use in practice. In vivo studies have generally used performance responses or biological markers such as tissue residues to determine effectiveness of binders. These measurements can only estimate binding indirectly because many factors and conditions affect results, binders need to be evaluated with different inclusion rates for different mycotoxins. However, if comparisons are to be made across studies, experimental criteria must be standardized. Even with standardization, products may vary significantly by lots, resulting in different results in vitro or in vivo and from study to study. Any negative effects of the binder should also be evaluated. Gathering the definitive information is complex, expensive, time consuming, and thus frustrating to an industry waiting for solutions.

Charcoal or activated carbon——————

Activated carbon is a general adsorptive material with a large surface area and excellent adsorptive capacity. It has been recommended as a general toxin adsorbing agent and is routinely recommended for various digestive toxicities. The effects of activated charcoal have been variable. Studies showed reduced aflatoxin residues in milk of cows consuming different sources of charcoal, but responses to charcoal did not exceed that seen with a clay-based binder (a hydrated sodium calcium aluminosilicate or HSCAS). Low levels (45 g/cow daily) of activated carbon did not significantly reduce milk aflatoxin residues, whereas clay-type binders (225 g/cow daily) or an organic polymer of esterified glucan (10 g/cow daily) significantly reduced milk aflatoxin. Responses to charcoal suggest that charcoal may not be as effective in binding aflatoxin as are clay-based binders. Activated charcoal may be important in binding zearalenone and/or deoxynivalenol. In an in vitro gastrointestinal model, activated carbon reduced availability of deoxynivalenol and nivalenol.

Silicate binders——————

Silicates are divided into subclasses, not by their chemistries, but by their structures. The silicate subclasses include neosilicates (single tetrahedrons), sorosilicates (double tetrahedrons), inosilicates (single and double chains), cyclosilicates (rings), phyllosilicates (sheets), and tectocilicates (frameworks). Silicates investigated as adsorbent materials are classified primarily as phyllosilicates and tectosilicates. Perhaps the most extensively studied of these materials is one designated a hydrated sodium calcium aluminosilicate (HSCAS). It is suggested that this specific silicate mineral can bind with aflatoxin by chelating the β-dicarbonyl moiety in aflatoxin with uncoordinated metal ions in the clay materials. Other silicates that have been studied include bentonites, zeolites, clinoptilolites. The clay group is a subcategory of the phyllosilicates. Bentonite is a general clay material originating from volcanic ash and containing primarily montmorillonite as the main constituent. Montmorillonite clay is a hydrated sodium calcium aluminum magnesium silicate hydroxide. Clays are silica sheets that are similar to other phyllosilicates but contain a high concentration of water. Zeolites are classified as tectosilicates consisting of interlocking tetrahedrons. The zeolite structure provides vacant spaces that form channels of various sizes allowing movement of molecules into and out of the structure. Zeolites can lose and absorb water without damage to their crystal structures.

Clearly much of the pioneering work with mycotoxin binders was done with silicates and specifically with the HSCAS material.Specific HSCAS included at 0.5% to 2.0% of the diet is well documented to adsorb aflatoxin and to prevent aflatoxicosis across species. Responses to HSCAS appear to be dose dependent.

This HSCAS is characterized as an “aflatoxin-selective clay,” is not a good adsorbent of other mycotoxins, and therefore, is not expected to be protective against feeds containing multiple mycotoxins. Cyclopiazonic acid, which has co-occurred with aflatoxin, is not adsorbed by HSCAS. Similarly little effect was seen, using a silicate material, ochratoxin toxicity but did demonstrate reduced T-2 toxicity.

Montmorillonite binds well with sterigmatocystin, a mycotoxin chemically similar to aflatoxin. Various clay products including a calcium bentonite reduce aflatoxin residues in milk of dairy cows. Several products were effective; however, a sodium bentonite reduced milk aflatoxin more than a similar amount of calcium bentonite. Diatomaceous earth has shown the potential in vitro to bind aflatoxin, sterigmatocystin, T-2 toxin, zearalenone, and ochratoxin . Zeolites have not proven to reduce the toxicity of T-2 toxin.

A number of studies have shown that chemical modifications have increased the binding of HSCAS with zearalenone, aflatoxin, ochratoxin, and zearalenone by an octadecyldimethylbenzyl ammonium treated zeolite.

Organic polymers as binders————–

Some complex indigestible carbohydrates (cellulose, polysaccharides in the cell walls of yeast and bacteria such as glucomannans, and peptidoglycans, and others), and synthetic polymers such as cholestryamine and polyvinylpyrrolidone can adsorb mycotoxins. Indigestible dietary fiber has adsorbance potential for mycotoxins. Alfalfa fiber has reduced the effects of zearalenone

Saccharomyces cerevisiae live yeast was shown to reduce the detrimental effects of aflatoxin. Fibrous material from the yeast cell wall was shown to have a potential to bind several mycotoxins. Esterified glucomannan polymer extracted from the yeast cell wall was shown to bind with aflatoxin, ochratoxin, and T-2 toxin, individually and combined. Additions of esterified glucomannan at 0.5 or 1.0 g/kg to diets supplying 2 mg of total aflatoxin resulted in dose-dependent responses in broiler chicks. Addition of esterified glucan polymer to aflatoxin contaminated diets of dairy cows has significantly reduced milk aflatoxin residues as per one study.

The esterified glucan polymer may have the capability to bind several mycotoxins. There are mechanism of binding with zearalenone. A glucan polymer bound both T-2 toxin and zearalenone in vitro.

Certain bacteria, particularly strains of lactic acid bacteria, propionibacteria, and bifidobacteria, appear to have the capacity to bind mycotoxins, including aflatoxin and some Fusarium-produced mycotoxins. The binding appears to be physical with deoxynivalenol, diacetoxyscerpenol, nivalenol, and other mycotoxins associated with hydrophobic pockets on the bacterial surface.

Other binders—————

A synthetic water-soluble polymer, polyvinlypyrrolidone (PVP), has been investigated as a binder of mycotoxins. Insufficient information is available to make any recommendations. PVP is reported to bind with aflatoxin and zearalenone in vitro.

Cholestyramine resin is used in human medicine for the reduction of cholesterol and functions through adsorption of bile acids. Cholestyramine has proven to adsorb zearalenone and fumonisins. An enzyme from a pure bacterial strain has been isolated that can de-epoxidize some trichothecenes.

Desirable characteristics of a binder—————–

A binder must be effective at sequestering the mycotoxin(s) of interest. In some cases, it may be of value to bind one specific mycotoxin, and in others to bind multiple mycotoxins. A binder should significantly prevent animal toxicity. There should not be serious detrimental effects on the animal, or at least detrimental effects should not outweigh the benefits. Costs should render its use practical and profitable. Animal/product residues of mycotoxins should not increase. There should be no detrimental effects on the animal food product. The binder should be physically usable in commercial feed manufacturing situations. Binder use and efficacy should be verifiable.

Mycotoxin control measures may require many approaches. In addition to binders or multiple binders, diets may be treated with other decontamination products. Animals may also be supplemented with antioxidants and other beneficial substances. Responses in dairy cattle to some of these products have been very encouraging. Overall results are variable by type and amount of binder, specific mycotoxins and their amounts, animal species, and interactions of other dietary ingredients.

The Effects of Mycotoxins on Cows———

The symptoms of mycotoxicosis in a dairy herd are not always obvious. Whilst mycotoxins can result in acute and obvious symptoms more often than not effects of mycotoxins are sub-clinical, and non-specific. They can be wide ranging depending on the levels and combinations of different mycotoxins involved, disease challenge, animal welfare, stress and a whole range of other factors.

Recognising when and to what degree mycotoxins are responsible for poor health and performance can be extremely difficult. The effects can be long lasting with cows taking many months to fully recover. It is highly likely that mycotoxins predispose animals to disease and are likely to exaggerate the symptoms of disease and also prolong the effects of a disease.

Effects include:

Reduced feed intake
Reduced milk output and reduced butterfat %
Suppression of the immune system
Decrease in rumen efficiency
Increased disease susceptibility
Mycotoxins are anti-microbial resulting in changes to rumen and gut microbial populations
Inflammation and damage to the digestive tract, intestinal haemorrhages, scour
Reduced nutrient absorption and impaired metabolism
Effects on endocrine and exocrine systems, hormone and enzyme levels
Metabolic problems, retained placentas, ketosis, displaced abomasums, acidosis
Infertility, metritis, cystic ovaries, poor conception rates, embryo loss, abortion
Lameness, laminitis, leg swelling, swollen hocks, liver abscesses, udder oedema
Increased somatic cell count and mastitis
Vaccine and drug failures and reduced effectiveness of antibiotics
Reduced longevity

Mycotoxins are often a factor which is contributing to long standing problems including high disease incidence, poor fertility and lower than expected milk yields.

Application in animal feed

The addition of adsorbent (binder) materials to animal feeds is very common for the prevention of mycotoxicosis, especially aflatoxicosis.

Adsorption

Mycotoxin binders are nutritionally inert substances added to animal feed in order to tightly bind and immobilize mycotoxins in the gastrointestinal tract of animals, thus reducing their bioavailability.

This process is known as adsorption, and it constitutes the most well-known approach to detoxification of mycotoxins.

Adsorption is a suitable strategy for aflatoxins, ergot alkaloids and ochratoxins, but it is not an efficient method to counteract trichothecenes, fumonisins and zearalenone.

Efficacious adsorption of mycotoxins depends on the polarity and shape of the mycotoxin, and the type of bonds that are formed between the toxin and the adsorbent.

Materials

Certain materials are better at binding than others.

Examples of binder materials include:

Silicates
Clays
Yeast
Charcoal

Bentonites are highly promising materials for adsorption of aflatoxin B₁ (AfB₁). Bentonites are clay minerals which result from the decomposition of volcanic ash consisting mainly of the phyllosilicate mineral montmorillonite (smectite). Bentonites have been reported to effectively decrease the inhibitory effects of dietary AfB₁.

Clay mineral binders alone are not an effective answer to all major mycotoxins. This holds especially true when it comes to counteracting Fusarium mycotoxins since their structures are not suitable for adsorption.

Activated charcoal represents a very unspecific binder, meaning that it also adsorbs nutrients.

How to choose the right product

An effective mycotoxin binder meets five key criteria, namely:

High adsorptive capacity
Irreversible – not easily undone
Specific – only binds mycotoxins
Safe
Scientifically proven through in vivo biomarker studies

Mycotoxin risk management

A complete mycotoxin mitigation strategy uses adsorption, biotransformation and bioprotection in order to protect farm animals, along with regular testing of feed ingredients.

Many industry practitioners use a combination of tactics, such as: