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By: B. Dolatkhah

Anti-nutritional Factors and Mycotoxins

Isfahan University of Technology

Definition of ANFs and Mycotoxins

Anti-nutritional factors and mycotoxins are distinct groups of compounds but they have many parallel features common precursors for certain compounds in both groups some ANFs share common chemistry with mycotoxins other ANFs and mycotoxins induce similar deleterious responses in animals

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IntroductionIntroduction

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some toxic and anti-nutritional effects include: haemolytic anemia lesions in the liver, kidney and central nervous system alterations in immune and endocrine function The net result is a depression in food intake, growth and

reproductive performance. diarrhoea and photosensitization may also occur with certain

toxicants

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Many ANFs and mycotoxins are metabolized in the digestive system and in the tissues of animals, resulting in detoxification or in promotion of adverse effects.

Rumen results in an efficient detoxification chamber The transformation of toxins generally results in less toxic compounds There are few cases where more toxic compounds are produced, e.g.

HCN or pyrogallol

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lectins Lectins or phytohaemagglutinins are proteins with a characteristic

affinity for certain sugar molecules or glycoproteins present in the membranes of different animal cells.

Lectins resist proteolytic degradation in vivo

Lectins are usually reported as being heat-labile Their stability varies between plant species Many lectins being resistant to inactivation by dry heat and requiring the

presence of moisture for more complete destruction

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They have the capability to directly bind to the intestinal mucosa

concanavalin A (jack bean) is a lectin that binds mainly to the lower regions of the intestinal villi.

The lectin of the winged bean with its requirement for more complex sugar structures, binds largely to the upper part of the villi.

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Binding and degradation of lectins by components of rumen liquorK. Baintner†, Sylvia H. Duncan, C.S. Stewart* and A. Puszta

Journal of Applied BacteriologyVolume 74, Issue 1, pages 29–35, January 1993

The binding of 15 different plant lectins to feed particles and microbes in rumen liquor, and their degradation were studied in vitro using radioactive iodine-labelled lectins

SBA, favin (Vicia faba lectin) and Con A were bound by hay and the particle fraction of rumen liquor.

Most pure bacterial strains preferentially bound lectins with specificity for glucose/mannose (favin and Con A), while rumen fungi reacted with SBA.

Clearly, as some lectins were not fully degraded in the rumen, they could be expected to depress the utilization of the diet not only in single-stomach animals but, possibly, also in ruminants.

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Tannins

Tannins are a heterogeneous group of high molecular weight phenolic compounds with the capacity to form reversible and irreversible complexes with proteins (mainly), polysaccharides (cellulose, hemicellulose, pectin, etc.), alkaloids, nucleic acids and minerals.

Tannins derive their main biochemical properties from...

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there are two biosynthetically-distinct classes of tannins: Hydrolysable tannins (HT;esters of gallic or ellagic acid and

glucose) Condensed tannins (CT; proanthocyanidins)

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Beneficial tannin effects

Low levels of tannins (< 5% dry weight) can benefit ruminants by: protecting protein from bacterial deamination protection for Cys, Met and Phe tannins suppress methanogenesis (directly or indirectly)

Reduction or improvement in digestibility of amino acids?? an increase in lactation, wool growth, reproductive performance and live-weight gain

without changing voluntary feed intake

reducing the detrimental effects of internal parasites in sheep and the risk of bloat in cattle (CT).

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Negative tannin effects

high dietary CT concentrations (>50 g/kg DM) depress voluntary feed intake, digestive efficiency and animal productivity

astringent taste alters the palatability of diets inhibits microbial enzymes involved in fiber and protein

degradation

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Tannin degradation Three crossbred Holstein x Zebu dry cows, fistulated in the rumen

were fed condensed tannins‑containing diet.

After three weeks of tannin diets the proportion of tannin‑resistant bacteria increased significantly.

Streptococcus gallolyticus (S. bovis) adapt to the presence of tannins in the rumen due to capacity of using a broad range of carbohydrates, especially those present in the

plant cell wall expressing several hydrolytic enzymes, including tannases and other phenolic

compounds decarboxylases

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existence of tannin-tolerant or tannin-degrading bacterial species appears to be a general phenomenon in animals adapted to a diet containing high levels of tannins.

Mechanisms by which bacteria can overcome inhibition include tannin modification/degradation dissociation of tannin–substrate complexes tannin inactivation by high-affinity binders membrane modification/repair and metal ion sequestration

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Amino acids

fermentation by rumen bacteria dimethyl

disulphide oxide

Reduction

dimethyl disulphide

precipitates the typical symptoms of haemolytic or kale anaemia in ruminants

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3-hydroxy-4(1H)-pyridone (3,4-DHP) is synthesized that is endowed with deleterious properties

mimosine may itself undergo decarboxylation within the tissues of the ruminant.

the requisite bacteria involved in the detoxification of the two DHP isomers

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Phyto-oestrogens

The phyto-oestrogens are a diverse group of isoflavonoid compounds (7 different structural groups) found primarily in legumes. soybeans; glycosides of the isoflavones, daidzein, genistein and

glycitein. subterranean clover and red clover; formononetin

Phyto-oestrogens are actively metabolized in the rumen

Rumen microbes may require up to 10 days to adapt to phyto-oestrogens.

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oxalate Oxalic acid, HOOC-COOH, is the simplest of the dicarboxylic acids (strong

acid; Pk1= 1.46 and pK2=4.40)

Oxalic acid is synthesized by a wide range of plants (such as forage) mainly as The soluble sodium or potassium salts The insoluble calcium salts

A few of them are forage plants that can cause oxalate poisoning in ruminants under certain conditions. Halogeton contains 17 to 30% soluble oxalate per dry plant weight (Cronin and Williams,

1965). The leaves of fodder beet may contain up to 10% soluble oxalate (Libert and Franceschi,

1987).

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When a ruminant consumes an oxalate-containing plant, the oxalate is metabolized in four possible ways:

1- soluble oxalate may be degraded by rumen microflora (Allison et al., 1977).

2- soluble oxalate may combine chemically with Ca to become insoluble oxalate, which is excreted in feces, reducing absorption of Ca.

3- soluble oxalate may be absorbed from the rumen into the blood stream where it can combine with serum Ca to form insoluble oxalate crystals (Blaney et al., 1982). This crystal may then precipitate in the kidneys and can cause kidney failure (Lincoln and Black, 1980).

4- ingested insoluble oxalate from plants may pass through the digestive tract without a harmful effect on the body’s metabolism (Ward et al., 1979).

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The ability of the rumen organisms to metabolize oxalates appears to be limited; if the intake is sufficient, both acute and chronic effects occur.

There are three syndromes following excessive oxalate ingestion in ruminants.

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Gossypol

Gossypol is a polyphenolic binaphthyl dialdehyde that can produce toxic effects in animals.

Gossypol exists in two forms: Free gossypol (FG) is toxic to animals the bound form is considered nontoxic because it can not be

absorbed in the digestive tract

Absorbed gossypol: retained in organs such as the kidney and in muscle is excreted via feces, urine, or milk

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Maximum residue limits of FG in food determined by the … were

Food and Agriculture Organization (FAO) ; 0.06% US Food and Drug Administration (FDA) ; 0.045%

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mycotoxins

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Definition; The secondary metabolism of fungi aflatoxins, ochratoxins, Fusarium mycotoxins, endophyte alkaloids,

phomopsins and sporidesmins

They can exert distinguished toxic effects on several animal species, and may lead to great economic losses in animal husbandry.

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The effects of mycotoxicoses are varying from immune suppression to death in severe cases, depending on toxin-related animal-related environmental factors

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Mycotoxicosis is difficult to diagnose

Symptoms of acute aflatoxicosis in mammals include: inappetance Lethargy Ataxia rough hair coat pale, enlarged fatty livers

Symptoms of chronic aflatoxin exposure include: reduced feed efficiency and milk production icterus decreased appetite

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Conversion of mycotoxins by the rumen floraConversion of mycotoxins by the rumen flora

ruminating animals are developing mycotoxicoses less frequently as the rumen flora acts as a first line of defence against mycotoxins.

rumen microbiota has the biotransformation ability of mycotoxins to less toxic or non toxic metabolites.

Protozoa are the most important ruminal microbial population in mycotoxin biodegradations.

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AflatoxinsAflatoxins They produced mainly by Aspergillus flavus and Aspergillus

parasiticus.

about 20 types of different aflatoxins are known.

They are mainly classified into … (Lerda, 2010).

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Aflatoxin B1

It is the most toxic mycotoxins (IARC, 2002)

AFB1 inhibits both DNA and RNA synthesis.

AFB1 could induce lipid peroxidation in rat livers causing oxidative damage to hepatocytes; potent hepatotoxin and hepatocarcinogen (Shen et al., 1994)

AFB1 in feed can be transferred into the milk

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AFM1

AFM1 has a similar toxicity and carcinogenicity to AFB1 (Van Egmond, 1989).

The excreted amount of aflatoxin M1 in milk of dairy cows: 1–2% (6.2%) of the ingested aflatoxin B1

feeding regimens rate of ingestion rate of digestion health of the animal hepatic biotransformation capacity actual milk production It varies between individual animals, from day to day, and from one milking to the next.

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The aim was to evaluate the in vitro dry matter disappearance (IVDMD) gas production ammonia-N formation

of an alfalfa hay based diet

Experimental treatments included four dose levels of AFB1 (0,300,600 and 900 ng/ml of medium)

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Reduction in gas production, dry matter digestibility and ammonia-N concentrations

The rate and cumulative gas production were affected (P<0.05) by increasing the level of AFB1 from 0 to 900 ng/ml; the gas production rate decreased from 0.071 to 0.051 cumulative gas production decreased from 196.4 to 166.0 ml/g DM

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some microorganisms in the rumen may be disturbed by aflatoxin

other rumen microorganisms may be able to degrade and transform aflatoxin to less toxic metabolites

a part of the ingested aflatoxin B1 is degraded in the rumen, resulting in the formation of aflatoxicol which is 18 times less toxic than aflatoxin B1.

42% of aflatoxin was degraded when incubated in vitro with rumen fluid.

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Ochratoxins The ochratoxins are a family of structurally related compounds

based on an isocoumarin molecule linked to phenylalanine (amide bond ).

Ochratoxin A (OA) and ochratoxin B are the only two forms to occur naturally as contaminants.

Ochratoxin A or OTA is produced by species of Aspergillus (A. ochraceus) and Penicillium (P.verrucosum, P. viridicatum) genera

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Effect of OTA: young animals with developed rumen ˂ pre-ruminant calves (Sreemannarayana et al.,

1988)

microorganisms of the rumen are able to hydrolyze the amide bond of OTA to produce OTα (lacking the phenylalanine moiety) which has a lower toxicity.

In healthy cattle up to 12mg of ochratoxin A per kg feed could be inactivated.

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OTA disappearance from the rumen arrive at half lives of : in vivo 0.6–3.8 h (average 2.8 ± 1.5 h) in vitro 0.2–12.7 h (average 3.6 ± 3.3 h)

the OTA concentration being completely back to 0 after (the range of

OTA doses applied in vivo was From 9.5 μg/kg bw to 500 μg/kg bw) : in vivo 6–13 h in vitro 6–32 h

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protozoa were found to be the most active microbes in OTA degradation

why incidentally small amounts of ochratoxin A could be detected in milk??

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Fusarium mycotoxins

produced by Fusarium species

Of particular importance are the trichothecenes zearalenone (ZEN) fumonisins

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1 .Trichothecenes

The trichothecenes are subdivided into four basic groups Both T-2 toxin and DAS are the most toxic.

DAS

DON or vomitoxin

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Pigs and poultry are very sensitive to T-2 toxin and DON

ruminants are less susceptible to these mycotoxins deoxynivalenol (vomitoxin) causes lowered feed intake, lowered

milk yield and fat content of milk. T-2 toxin causes rejection of feed, lesions in gastrointestinal tract,

and maybe internal bleeding.

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A new species of bacterium of the genus Eubacterium (Eubacterium strain BBSH 797) was separated from bovine rumen fluid which showed the potentiality of biotransforming the epoxide group of trichothecenes into a diene (Schatzmayr et al., 2006).

In ruminants DON is converted almost completely into the less toxic DOM (the de-epoxidized metabolite of DON) by the rumen flora.

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2 -Zearalenone (ZEN)

Zearalenone is a phyto-esterogenic compound.

zearalenone affects negatively reproductive organs decrease in pregnancy rate disrupts hormonal equilibrium

The ovine metabolism of ZEN has been proposed to involve the synthesis of at least five metabolites; zearalanone, a-zearalenol, b-zearalenol, a-zearalanol and b-zearalanol.

Pigs are highly susceptible / chickens and cattle show lower sensitivities

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α-zearalenol has a higher oestrogenic potency compared with the parent zearalenone

lower rate of absorption interconversion in the liver to the

less potent β-zearalenol

90% 10%

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3-Fumonisin

metabolties produced by Fusarium proliferatum, and F. verticillioides

Three members of this group (fumonisin B1, B2 and B3) may occur together in maize.

FB1 is the most toxic promoting tumor in rats (Gelderblom et al., 1988).

Fumonisins inhibit the synthesis of ceramides from sphinganin. The recycling of sphingosins is blocked, resulting in cell dysfunction followed by cell death.

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Fumonisins mostly affect horses, pigs and poultry.

Ruminants are much less sensitive feeding fusarium-contaminated wheat to dairy cows led to

increased crude protein degradation and a lower molar percentage of propionate in the rumen.

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conclusionsconclusions Plants and fungi synthesize a wide range of substances with anti-

nutritional and toxic effects in farm animals.

Extensive rumen and tissue metabolism may occur in farm animals to initiate or enhance the potency of some of these copounds.

The toxic and anti-nutritional effects include haemolytic anaemia, lesions in the liver, kidney and central nervous system and alterations in immune and endocrine function.

The net result is a depression in food intake, growth and reproductive performance, but other effects such as diarrhoea and photosensitization may also occur with certain toxicants.

Thank You

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