Mycotoxins: a simple explanation for a complex topic.
BIOMIN Holding GmbH, Herzogenburg, Austria.
Mycotoxins' impact on swine performance In countries where livestock breeding, namely pigs, play an important role and where the animal potential is stretched to its limits, every factor disturbing the industry and the animal's efficiency, such as mycotoxins, should be eliminated.
Mycotoxins are naturally occurring secondary metabolites produced by certain moulds/fungi as a result of their organic processes. There are some secondary metabolites of fungal origin medicinal or industrial applications, namely Penicillin. Unfortunately, most mycotoxins are known to hazardously contaminate crops and consequently animal feeds and animal products, causing significant economic losses associated with their impact on animal and human health, animal productivity and domestic and international trade.
Animals vary in their susceptibility to mycotoxins, according to the age and the species of animal and the specific toxin involved (Pier et al, 1980). In general, pigs are considered the most susceptible animals to mycotoxin contamination and amongst them; young animals and female breeders are the most sensitive.
The producing fungi
The mycotoxin-producing fungi fall generally into two different groups: those that invade the plants on the field before harvest – the field fungi – and those that occur after harvest – the storage fungi. Avoiding fungi contamination on the field is quite difficult, if not impossible, since by the one side, there is a broad range of factors weakening the plant's natural defense, thus promoting their growth and mycotoxin formation, namely droughts, floods, poor fertilization, high crop densities, insect or mechanical damage and late harvesting. Avoiding it during storage can be done to some extend with proper storage conditions, controlled temperature and moisture content and good management practices, but in general it is unattainable to totally eliminate the problem. On the other side it is also known that these types of fungi have very few nutritional, environmental and reproductive requirements, thus their ability to survive is well developed.
Concerning the detection and analyses of mycotoxins, these are very difficult tasks. For one mycotoxins are invisible, odorless and tasteless and occur heterogeneously in the feed, in the so-called "hot-spots" or nuggets. Additionally, mycotoxins can be bound to certain nutrients as masked-mycotoxins making them undetectable by analytical procedures. Further development in that area of detecting masked mycotoxins is still needed yet unlikely to materialize due to lack of funding and interest. Finally, one can never directly correlate mycotoxin concentration with the effects due to the synergistic effects mycotoxins have in conjunction with each other, meaning that the effects of one mycotoxin might be amplified by the co-occurrence of another. However, based on the knowledge that mycotoxins are very stable to chemical and high temperature treatments (Agag, 2005) that normally kill the fungi spores, it should be clearly understood that in spite of moldy grain having a higher probability of mycotoxin contamination, the apparently sound grains may also be affected by this problem, therefore a farmer may well be feeding these poisonous substances to his animals without even noticing it.
There are many factors that amplify the mycotoxin challenge: 1) Each plant can be infected by more than one fungus; 2) Each fungus is able to produce more than one mycotoxin; 3) Mycotoxins can be produced in many stages of the feed manufacturing, not only before and during harvest but also during storage; 4) Each feed is composed by different commodities; 5) The world trade of feedstuffs has spread mycotoxins amongst commodities worldwide, making it difficult to relate a known location with a specific mycotoxin. Consequently, there is a great probability that many mycotoxins are present in a pig ration, thus increasing the odds of interactions between mycotoxins and the occurrence of synergistic effects, which are of great concern in livestock health and productivity.
Mycotoxicoses are the animal or human diseases caused by mycotoxins' ingestion, inhalation or contact with the skin. The effects of mycotoxicoses in animals are diverse, varying from immune suppression to death in severe cases, depending on toxin-related (type of mycotoxin consumed, level and duration of intake), animal-related (animal species, sex, age, breed, general health, immune status, nutritional standing) and environmental (farm management, hygiene, temperature) factors (Heidler, 2003). It can be said that poor management and health conditions on a farm will function as interactants, thus amplifying mycotoxins' negative effects. In the case of pigs, piglets and female breeders are the most susceptible animals, but attention should be given to finishing animals as mycotoxins can be carried over to blood, muscles and appear in the meat. To prevent this and to minimize mycotoxins' occurrence in human food, limits have been imposed worldwide regarding mycotoxin concentration in animal feeds.
For practical consideration in the feed manufacturing process aflatoxins, trichothecenes, zearalenone, ochratoxins, and fumonisins are of particular interest, though the extent of harm each toxin (group) can cause is highly species-dependant (Binder, 2007). Although there are geographic and climatic differences in the production and occurrence of mycotoxins, exposure to these substances is worldwide (Kuiper-Goodman, 2004). Nevertheless, a preferred pattern in terms of temperature and water activity for fungal growth and mycotoxin production can be established to some extent. For example, aflatoxins are produced by A. flavus over the temperature range of 15 - 37°C, at least. It is not possible to specify an optimum temperature for the production of the toxins, although production between 20 - 30oC is reported to be significantly greater at higher than at lower temperatures. In general, production of aflatoxins appears to be favored by the presence of water. In the case of F. graminearum growth, the optimum temperature has been estimated at 24 - 26°C. Different information is available regarding the most favorable temperature for the production of trichothecenes and zearalenone by this fungus. In general, the production of these mycotoxins is ubiquitous, more prevalent in warm and moderate climates. Ochratoxin A is produced by A. ochraceus within the temperature range 15 - 37oC, with an optimal production at 25 - 28oC. P. verrucosum grows within the temperature range 0 - 31oC and low humidity of 0.80; ochratoxin A is produced over the whole temperature range. Significant quantities of ochratoxin can be produced at a temperature as low as 4oC, and humidity as low as 0.86 (FAO, 2001). In the case of fumonisins, the optimum temperature for production was between 15 and 25°C, in a study with maize (Samapundo et al, 2005).
Figure 1 - Some effects of mycotoxins in pigs
Effects os Mycotoxins On Pig Performance
Animal performance is influenced by many factors. The major factors contributing to the profitability of the pig production industry are the number of pigs produced per sow and the feed cost of producing those pigs. The final objective of the pig producing industry is to maximize the amount of meat (kg) produced per sow per year, while maintaining sow condition and health.
In a feeding herd, there are some parameters that should be measured in order to assess its profitability, as they will influence the variable costs of a farm (adapted from ©Boehringer Ingelheim Animal Health GmbH, 2006).
Economic impact of mycotoxins in the pig feed
The occurrence of mycotoxins in feed has negative impact in the performance parameters, confirmed by several scientific studies and farm case studies.
- A 715 ppb deoxynivalenol (DON) feed contamination increased the piglet mortality rate from 2.5 to 10.2%.
Mortality will have a great economic impact because all the money invested will generate no return.
- A simultaneous contamination of 500 ppb of ochratoxin A (OTA) and 250 ppb of zearalenone (ZON) significantly reduced the daily weight gain and thus the final body weight of 63-days old piglets.
This will be reflected either by delayed animals to market or in a lower weight at the time of harvest.
- The co-occurrence of 250 ppb ZON and 1000 ppb DON in piglets' feed significantly lowered their daily body weight gain and final weight gain.
The reduced feed conversion will affect the feeding costs due to the higher amount of feed that is required by the animals to have a weight increase of 1 kg.
Some examples on the economic impact of a poorer performance can be observed in the table below.
1) 1% change in mortality is worth 1.49€ a pig (not including labor or medication costs). 2) 0,1 change in FCR represents 2.09€ per pig (when average feed cost is 223.62€/ton). 3) 50g/day change in growth rate is worth 1,57€ per pig if pigs are sold at the same weight.
Besides having a direct negative impact on animal performance directly related with the molecules' toxicity, mycotoxins have a negative effect in the nutrient uptake, or in other words, they inhibit the absorption of nutrients by the animals (Hunder et al, 1991; Smith, 1992; Meloche et al, 1995; Maresca et al, 2001; Maresca et al, 2002; Dänicke et al, 2004; Awad et al, 2004; Williams, 2005; Awad et al, 2005). The objective of feeding programs is to increase nutrient intake.
It is every producer's desire to be competitive and profitable. This is especially important in the current market, where price fluctuations are unpredictable and often represent a great loss for the pig producer. The counteraction of mycotoxin related problems in a farm will not only increase animal performance but, and most importantly, will consequently improve the pig producer's profit, also leading to the production of healthier, higher quality and safer products to meet the market's demands. In a society that is increasingly scared about animal disease outbreaks, mycotoxins in animal feeds represent a great risk and therefore should not be accepted. Animal producers are one of the key-players in the production chain thus it is also their responsibility to counteract the mycotoxin problematic.
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