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Have our birds become more vulnerable to disease due to mycotoxins?

 
Ruben Beltran, Biomin
In 1955 the word mycotoxicosis was first used to describe diseases, which were caused by fungal toxins. Worldwide, approximately 25% of crops are affected by mycotoxins annually (Cast, 1989). The estimated 25% contamination of the world's annual crops would potentially extrapolate to billions of dollars (Trial et al., 1995). Mycotoxins have been known to make animals more susceptible to disease leading to illness or sometimes even death. Grains that have been exposed to severe environmental conditions such as temperature and humidity are only a part of why mycotoxins occur. Other factors that lead to the development of mycotoxins can be the time of harvest as well as storage conditions of the grain. Some of the strategies that are used to prevent mycotoxin contamination include the following: careful screening of incoming ingredients, proper storage of feedstuffs, cleaning storage bins and feed milling equipment. Even following strict guidelines and management practices producers often find themselves owning grain or feed that has been contaminated with mycotoxins.

 

Getting Realistic about Mycotoxins

 

The effects of mycotoxins in animals depend on: age, physiological state, nutrition, and the level of toxicity that can often make mycotoxicosis difficult to diagnose. The definition of mycotoxicosis is ''Diseases caused by exposure to mycotoxin-contaminated feedstuffs or foods''. Mycotoxins exert their effects through three primary mechanisms:

 

1. A reduction in amount of nutrients available for use by the animal

   (Kao and Robinson, 1972)

 

2. Effects on the endocrine and exocrine systems (Klang et al., 1978)

 

3. Suppression of the immune system (Sharma, 1993)

 

Mostly not only one mycotoxin occurs but a variety of different ones. Especially the Fusarium sp. produces a big group of mycotoxins. Therefore oftentimes mycotoxins produced by this type of fungus occur simultaneously (DON, T-2, ZON, etc.) These agents can act synergistically under field conditions resulting in major losses of production especially when coupled with stressors associated with commercial poultry rearing situations and their exposure to potential harmful organisms (ex. Salmonella spp., E. coli). Therefore it can be stated that there are no safe levels of mycotoxins present (Hamilton, 1984). Of the major species of poultry that are used for meat type / egg production, these animals tend to be fairly resistant to fumonisin, deoxynivalenol, and zearalenone. However if one of these mycotoxins is detected it can be a marker that mold activity has occurred in the ration leading to the development of other mycotoxins.

 

Prevalent mycotoxins in poultry are produced by Fusarium, Aspergillus, and Penicillium species. Aflatoxins, T-2 toxin, DON (deoxynivalenol), and DAS (diacetoxyscirpenol), are considered to be the main causes for the visible declines in production. In general these groups of mycotoxins can negatively affect and lead to the following outcomes:

 

Feed intake

    • Bruising
       
    • Increased incidence of diarrhea and blooding feces
       
    • High incidence of diseases associated with poor immune function
       
    • Pale liver syndrome (see picture 3)
       
    • Beak/vent lesions (tissue edema see picture 1,2 and 4 - 6)
       
    • Altered immune mechanism resulting in vaccine failures
       
    • Poor or impaired feathering
       
    • Sudden drop in egg production
       
    • Weak or thin egg shells
       
    • Decreased quality of egg components

  

Picture 3: pale liver due to aflatoxin

 

What other problems do mycotoxins cause?
 

There are many other production problems that can be associated with the contamination of mycotoxins. Table one and two represent the toxic effects in both, broilers and layers alike.

 

Table1: Toxic effects of dietary trichothecene mycotoxins in broiler chickens

 

 

Mycotoxins

Dietary level

Time of exposure

Effects 

(mg/kg)

(weeks)

T-2 toxins

4

1

Oral lesions

4

3

Neural disturbances, Decreased growth rate

4

3

Reduced weight gain, hepatic hematomas

4

Abnormal feathering

3

0.4

7

Oral lesions

1-4

3

Oral lesions: decreased feed intake & weight

8-16

11

Decreased weight gain; oral lesions

4-16

3

Oral necrosis; reduced feed consumption

50-300

3

Reduced hematocrit, lymphoid atrophy, anemia;

8

3

Oral lesions, decreased body weight

DAS

5

3

Oral lesions, decreased feed intake and weight

4-16

3

Oral lesions, growth retardation

1-2

3

Oral lesions, growth retardation

4-8

3

Decreased body weight

DON

1.87

1.87

No adverse effects

16

3

Reduced body weight gain and feed efffciency

 

Table 2: Toxic effects of dietary trichothecene mycotoxins in laying hens  

Mycotoxins

Dietary level (mg/kg)

Time of exposure

Effects

(weeks)

T-2 toxins

16

4

Decreased feed intake and egg production; oral lesions

8

8

Decreased feed consumption, egg production, shell thickness;

decreased hatchability; oral, crop, and gizzard lesions

4-8

4

Egg production slightly decreased (not statistically significant)

16

4

Reduced feed intake, body weight, egg production

12

18 days

Decreased feed intake and egg production; Wyatt et al., (1978)

decreased egg weight; oral lesions

1-10

4

Oral lesions; decreased feed intake and egg production

2

24 days

Decreased hatchability of fertile eggs

DAS

0.5

4

Oral lesions; decreased feed intake and egg production;

2

24 days

Increased incidence of soft-shelled eggs

DON

0.35-0.7

70 days

Decreased egg and shell weight, shell thickness

1-5

24

No adverse effects on health or productivity

20

12 days

No adverse effects

2.5-4.9

70 days

Increased incidence of chick developmental abnormalities

 

Modified from S. Leeson, G. Diaz, and J.D. Summers (Poultry Metabolic Disorders and Mycotoxins 1995)

 

Economic consequences of mycotoxins in poultry production

 

Animal and poultry nutrition represents a challenging mixture of not only animal requirements and production goals but also involves heavily on economics. Feed is widely recognized as being the most important component in the cost of producing chicken. A common rule of thumb is that feed represents approximately half the cost of producing an eviscerated whole chicken (Aho, 2004).

 

The financial impact in which mycotoxins cause economic losses in poultry and livestock production can be calculated by quantifying performance. Some parameters, which can be used to measure production losses, can be mortality, feed conversion ratio, egg production, egg quality, and percent hatchability. The effect of oral lesions in breeders can result in reduction of feed consumption due to irritation around areas of the beak and can ultimately cause a reduction in laying which is often a result from exposure of 1-4 ppm of tricothecene (T-2 toxin) contaminated feed (Diaz, Cortez, and Roldan; 2005) (see picture 1 and 2).

 

 

 Picture 1 and 2: T-2 toxin- oral lesions located in mandibular mucosa

 

A practical example of an economic loss due to mycotoxins on a parent broiler

breeding enterprise would be:

 

Integrators that suffered from a decline in egg production and a reduction in percent hatchability. A typical scenario from this result would be that these integrators would then have to purchase broiler chicks or eggs from an outside source to compensate for the losses from their in-house breeder flocks. A 10% drop in egg production, coupled with a 5% reduction in hatchability for 20 days in a flock of 25,000 40-week-old broiler breeders will reduce production by 19% (ASA).

 

 Picture 4, 5 and 6: DAS- Oral lesions located in the laryngeal mound and tongue.

Projected value of the loss of 45,625-day-old broilers at $8,193 taken into consideration the current production values which include a purchase price of 15 cents per unit (ASA).

 

In Conclusion

The importance of good and sound nutrition is nothing new. Today, nutrition is as important as ever in maintaining a healthy animal. Mycotoxins among other things will affect your bottom line whether it's an acute outbreak or subtle changes in production parameters.Today many companies, researchers, and universities are finding ways to improve our animals'environment and well being. Yet despite the hard work and efforts the questions still remain but can be somewhat understood and that is, " Have our birds become more vulnerable to disease due to mycotoxins and what do mycotoxins do to our overall profitability?"

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