26 May 2020
POINTS FOR REFLECTION ON MYCOTOXICOSES
One of the great challenges faced by intensive animal production and public health is the high incidence and prevalence of fungi and their metabolites found in grains and oilseeds used in animal feeds.
This problem is not recent, since during the Middle Ages in Europe one of the first reported cases of mycotoxicosis was attributed to the consumption of rye contaminated with Claviceps purpurea, which caused the disease known as “Saint Anthony’s Fire”. The disease was characterized by a high incidence of necrotic lesions, nervous signs and high infant mortality rates, and its treatment was linked to rituals and religious ceremonies. Currently, the disease remains present and is known as ergotism.
Currently, some questions are emerging and deserve answers, such as:
How far we are from those “magic and religious treatments”?
Are the incidence and prevalence on the mycotoxin reports analyzed and correlated in a constant and precise way, considering each particular case?
If grain cleaning is an efficient preventive measure, why has the practice not been disseminated?
Mycotoxins are toxic compounds that alter cellular metabolism and cause tissue damage in the exposed organism, although the presence of mycelia is not obligatorily correlated with mycotoxin production.
Currently, it is known that mycotoxins are not only defense mechanisms against toxigenic fungi, but they are also produced and eliminated as a result of its metabolic activities. This production increases when the fungi are subjected to stress conditions.
The severity of the clinical picture in which the tissue lesions and metabolic disorders participate, are influenced, among other aspects, by:
The species
The mycotoxins and their concentrations
The exposure time and its interactions
All these aspects lead us to reflect…
How do tissue lesions and metabolic effects occur? How are they dealt with?
Which are the criteria for the application of preventive and/or control measures?
Can we treat tissue lesions ignoring the metabolic disorders to reestablish the health status?
In 2003, the economic losses due to mycotoxins in USA and Canada were estimated at USD 5 million. Sixteen years later, they are still present, in spite of great advances in technological developments and the generation of scientific information.
There is not a comprehensive program to apply preventive measures and control mycotoxins from the growth and development of the plant in the field to the effects of finished products (milk, meat and eggs) on public health.
This makes the results of individual actions taken in each section inefficient and unpredictable, leading to a variable response in terms of crop yield, storage losses, productive parameters, immunity, severity of the disease, and even death in humans.
The consumption of low and constant doses of mycotoxins (even in compliance with the standards established in health legislation) should not be underestimated due to its cumulative effect.
It is difficult to determine what the losses of productive parameters are attributed to, since there is a close link between the toxic effects of mycotoxins and fungi on the reduction of quality and nutritional content of the ingredient. Also, both directly affect at least the feed conversion rate.
Under research conditions, as mycotoxin levels and consumption time are controlled, the necropsy findings and metabolic disorders are predictable and uniform, allowing for a correlation between effect and concentration.
This definitely does not happen underfield conditions since many mycotoxins are present, which are not uniformly distributed in the feed. This leads to variations in the amount consumed and frequency of consumption. Also, there is an interaction between them and several conditions that lead to different responses, even in animals from the same group.
A fundamental premise of research is the reproducibility of results under the same methodology. This is not feasible as the intensive production systems do not have equal conditions.
Mycotoxins in poultry production
In poultry production, major economic losses are caused by the presence of aflatoxin, ochratoxin, T-2 toxin, diacetoxiscirpenol (DAS), deoxinivalenol (DON), zearalenone and fumonisin.
The mycotoxins can be classified as polar and non-polar molecules. This is an important aspect when selecting products to control mycotoxins through deactivation or capture.
It is important to note that these products have no effect on the mycotoxins and their metabolites circulating in the blood or stored in tissues. In effect, they are xenobiotic agents responsible for alterations by recirculation, making it hard to determine accurately the amount of mycotoxins present in an organism and responsible for variable responses in terms of production, reproduction, clinical signs and lesions.
Effect of aflatoxins in poultry
The effect of aflatoxins in birds at different ages and zootechnical purposes is exemplified by the reduction of the following concentrations:
Bile salts (up to 56%)
Digestive enzymes such as amylase, trypsin and lipase (up to 35%)
Considering that the nutrient concentration is higher in broiler chickens than in laying hens and that the starter diets fed to broilers contain higher protein levels and lower energy levels compared to the finisher diets, both lipid consumption and the substrates in which the enzymes act are different.
¿The effect of aflatoxins on the production of bile salts and the action of digestive enzymes on the substrates present in the diet may affect, in the same order of magnitude, broilers, hens or chicks, in both starter and finisher phases?
The hepatotoxic effect caused by aflatoxins produce alterations in protein synthesis.
Moreover, liver function is altered according to the degree of fatty infiltration, as explained below:
In broilers, fatty infiltration (and, in severe cases, fatty degeneration) is a common problem. This is important due to the high lipid concentrations in poultry diets.
In laying hens, fatty infiltration is a physiological condition for yolk formation.
For this reason, the infiltration is a negative factor added to the already existing hepatotoxic factor of aflatoxins in broilers.
Analysis for mycotoxin detection
Various techniques are currently used, such as:
Liquid chromatography
Coupled gas chromatography
Thin layer chromatography
Immunotechniques such as ELISA
Immunoaffinity columns that are used as a purification step previous to liquid chromatography or combined with mass spectrometry, the latter being able to simultaneously analyze different types of mycotoxins.
Despite the technology and scientific advances in the knowledge of mycotoxins, combined with the development of products that capture or deactivate (by enzyme action) them and the local and global legislative regulations, it can be stated that the instruments for their prevention and control actually exist. So….
Why do they continue to cause significant losses? However, the answer should not be simplistic, since each situation has unique predisponent factors which interact closely to one another.
The analyses only represent the result of a particular sample at the time of the test, and it is not even possible to ensure that they correspond to the time of sampling. Also, different results can be observed in the same fractionated sample, despite having performed an excellent sampling, using the most accurate and sensitive analytical techniques. If the fungi are present, it is a dynamic process. If they were not present, they would be randomly distributed in the grains and/or finished feed.
Today’s actions do not guarantee the control of tomorrow. The analyses could no doubt be a very useful tool if properly used, correlated and interpreted, together with other factors involved. This can indicate the way forward in controlling and/or preventing mycotoxicosis.
The agricultural sector can produce grains and oilseeds contaminated or not with mycotoxins. This situation does not affect to the same extent the farmer, the stockholder, the food manufacturer, the livestock farmer and the final consumer.
These sectors are an integral part of the productive chain and cannot be seen as independent activities. Each of them plays a role that positively or negatively affects productive outcomes and public health.
How can we establish measures to prevent mycotoxicosis?
It is known that in each part of the chain there are different conditions, which require different measures. If they are not
applied in a comprehensive manner the expected results are not the same. One example is the grain cleaning, the most efficient measure to remove broken kernels, which are the main substrates for the growth of fungi.
Some areas have not received the necessary attention, as is the case of storage silos, which inevitably favor the growth of fungi due to the environmental conditions and due to the fact that they are not under supervision of the feed mill. Also, in most cases the internal cleaning is not done according to the required times and methodology because the silos contain food – and this does not allow the cleaning.
Now what?
How far we are from those “magic and religious treatments”?
Are the incidence and prevalence on the mycotoxin reports analyzed and correlated in a constant and precise way, considering each particular case?
If grain cleaning is an efficient preventive measure, why has the practice not been disseminated?
Why is that the silos that store foods for long periods of time and represent a high-risk factor have not received due attention at least in terms of cleaning and knowledge of microenvironmental conditions?
