O/T ( Excellent) Understanding and Preventing Feedborne Mycotoxins (Part 1)

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Understanding and Preventing Feedborne Mycotoxins (Part 1)

http://www.agribusinessweek.com/understanding-and-preventing-feedborne-mycotoxin\

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Mycotoxin contamination of feed is, in many ways an unavoidable reality. It is

believed that over 25 percent of the world's grain supply is contaminated with

mycotoxins. Mycotoxins can be carcinogenic and hepatoxic to both animals and

humans.

To fully understand the effects of feedborne mycotoxins on livestock and

poultry, we will let Dr. Trevor K. , professor from the Department of

Animal Science of Ontario Agricultural College in Guelph, Ontario, Canada, and

external consultant of Alltech in Kentucky, USA, answer some of the frequently

asked questions on feedborne mycotoxins in this issue:

Question: What are mycotoxins?

Answer: Mycotoxins are structurally diverse secondary metabolites of fungi that

grow on a variety of feeds and foods consumed by animals and man, respectively.

These chemically stable compounds are toxic to livestock when consumed in

biologically significant amounts. The resulting diseases are referred to as

mycotoxicoses.

Q: What are the predisposing factors of fungal growth and mycotoxin production

in feed grains?

A: Mold growth and mycotoxin production on feed grains are influenced by many

factors, but the most important of these is moisture. Stored grains should

contain less than 15 percent moisture to minimize mold growth.

Q: What are some of the trends favoring global proliferation of mycotoxins?

A: Several trends have tended to increase the severity and economic importance

of mycotoxins in animal and poultry agriculture in recent years. These trends

are as follows:

• Recent global weather patterns have been irregular with heavy rainfall and

flooding in some areas coupled with drought and unusual frosts in other regions.

• Drought stress can also lead to increased fungal penetrations of grains. The

result has been an increased frequency of reports of mycotoxin contamination of

feed grains. Some tropi=cal and semi-tropical countries are reporting Fusarium

contamination of crops where only aflatoxin was previously detected.

• Another trend contributing to the frequency of mycotoxin contamination of

feeds is improved global trading transportation systems and global trading of

agricultural commodities. This allows more extensive shipping of grains and

other feed components throughout the world. The result is that complete feeds

are likely a more complex blend of feedstuffs with more widely varying

geographic origins than was seen in the past. The potential for aflatoxins and

mixtures of Fusarium mycotoxins to be contaminants in feeds is, therefore,

enhanced.

Q: What are the most commonly recognized feedborne mycotoxins?

A: The most commonly recognized feedborne mycotoxins are the aflatoxins and the

Fusarium mycotoxins. Fusarium fungi are commonly found in temperate climates;

and Fusarium mycotoxins are likely the most economically significant grain

mycotoxins on a global basis.

Q: What are some of the Fusarium mycotoxins found in feed grains?

A: The numerous Fusarium mycotoxins are very diverse in chemical structure and

in the characteristics of the mycotoxicoses they produce. These toxins include

the trichothecenes, the fumonisins, zearalenone, moniliformin, and fusaric acid.

Q: What are the major effects of Fusarium toxins on livestock and poultry?

A: Here they are:

1. Fumonisins

a. Immunosuppression

b. Leukoencephalomalecia in horse

c. Lung edema in swine

2. T2 Toxin

a. Inflammation of the GI tract

b. Females don't return to estrus

c. Immunosupression

d. Vomiting

e. Beak and palate lesions

f. Anorexia

g. Blood pressure reduction

h. Increased brain tryptophan levels (serotonin precursor)

i. Reduced appetite

3. Zearalenone (Zen, Zea, F-2 Toxin):

Found worldwide, particularly in corn(maize).

a. Uterine prolapse

b. Hyperestrogenism, abortions and embryo reabsorption

c. Return to estrus

d. Anestrus

e. Ovarian and testicular atrophy

f. Reduction in litter size

g. Estrogenic properties

4. Vomitoxin/Deoxynivalenol (DON): Swine are the species most sensitive to

dietary deoxynivalenol. Poultry are less sensitive and ruminants are the most

resistant due to the action of the rumen microflora.

a. Poor performance

b. Anorexia

c. Vomiting

d. Increased brain tryptophan levels

5. Fusaric Acid

a. Lethargy

b. Anorexia

c. Vomiting

d. Low blood pressure

e. Inhibitors of cell protein syntheSi,

f. Increased brain tryptophan levels (serotonin precursor)

g. Reduced appetite

Q: How hazardous are feeds contaminated with Fusarium mycotoxins?

A: The non-specific nature of the symptoms of tricothecene toxicosis, including

reduced feed consumptions, reduced growth and immunosuppression, make it

difficult to confirm trichothecenes as the cause of lost performance. The cause

could also be improper management practices or a wide range of health factors.

Q: Are there toxicological interactions between Fusarium mycotoxins?

A: It is now clear that toxicological synergism between different Fusarinrn

mycotoxins can increase the toxicity of a given diet and incomplete analysis

can, therefore, give false security as to the potential hazard posed by the

feeding of contaminated grains. It is also important to remember that many

different components of a complete feed can be vectors for mycotoxin

contamination. Our studies indicated that the fusaric acid content of complete

feeds can exceed that found in individual feedstuffs. This has since been

attributed to fusaric acid contamination of soybean meal. Fusaric acid has been

found in soybean plants and is considered a phytoxin in various vegetables

species.

Note: Our mycotoxin expert, Dr Trevor K. , is a native of Vancouver British

Columbia, Canada. He's a graduate of' Chemistry from the University of British

Colurnbia in 1970 and subsequently completed an M.Sc. inAnimal Nutrition at the

University oj' Manitoba (1974) and Ph.D. in Animal Nutrition at Cornell

University (1977). He has been a, faculty member at the University of Guelph

since that time. His research interests are monogastric nutrition and feed

toxicology, including the etiology and treatment of Fusarium mycotoxins and the

metabolic effects of feed-borne biogenic amines.