Mycotoxin contamination in commonly used raw materials within South African sheep feedlots and the effect of mycotoxin deactivators on production parameters and profitability
When stressed, fungi produce mycotoxins. These mycotoxins are, as the name suggests, toxic in many ways to animals and humans alike. Mycotoxins have a low molecular-weight and are produced as a secondary metabolite by fungi. Mycotoxins that cause health implications in vertebrates include Aflatoxins (produced by Aspergillus species), Ochratoxins (produced by Penicillium and Aspergillus species), Ergot Alkaloids (produced by Claviceps species) and Fusariotoxins (produced by Fusarium species) which include Zearalenone, Fumonisins, Vomitoxin and Trichothecenes. Mycotoxin formation is common during storage but occurs during all stages of production and/-or processing of grains. In production animals, mycotoxins are responsible for a significant decrease in animal performance. The decrease in animal performance is due to direct influence on animal health and/-or influence on nutritional value of feed. Due to the possible decrease in production, mycotoxins are economically significant.
Various factors affect fungal growth and subsequent mycotoxin production. The most important factors include environmental conditions, physical damage to the crop, and the presence of fungal spores. Suitable temperatures, combined with sufficient moisture and oxygen, are favorable environmental conditions for mycotoxin production. Physical damage to the crop, including insect induced damage or mechanical damage pre/post-harvest, predispose crops to fungal and subsequent mycotoxin contamination. Moreover, improper practices during harvesting, handling, transportation and processing further increase the risk of mycotoxin contamination.
Since a single fungus can produce different mycotoxins, and multiple mycotoxins can contaminate a single crop, the majority of crops are co-contaminated. The combination of multiple mycotoxins increases the interaction amongst toxins and results in synergistic or additive adverse effects. The most important adverse effects in livestock include immunological, reproductive, and performance disorders. The toxic effect depends on the type of mycotoxin, the amount consumed, exposure time, interactions between toxins, and animal sensitivity. Moreover, the different acute and chronic effects on animals depends on the species and the susceptibility of the specific animal within the species. Ruminants are generally more resistant to the adverse effects due to the partial detoxification of mycotoxins by rumen microbiota. In contrast, monogastric animals, specifically swine, poultry, and aquatic vertebrates, are highly susceptible to mycotoxicosis.
Though ruminants are generally more resistant to mycotoxicosis, their inherent detoxification ability is only effective in non-stressed animals. Sheep kept under intensive conditions often experience increased stress levels, decreasing the detoxification ability of these animals. When sheep are kept under intensive conditions, an increase in dry matter intake and therefor higher passage rate is seen. These higher passage rates result in shorter rumen retention time and subsequently reduce the time available for mycotoxin detoxification by rumen microbiota further contributing to decreased detoxification ability.
It is hypothesized that feeds contaminated by mycotoxins decreases animal performance, and that the use of the mycotoxin deactivators will mitigate the effects of mycotoxins in the feed. The aim of the study is the following:
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To determine the extent of mycotoxin contamination in feedstuffs commonly used in South African sheep feedlot diets.
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To determine the dominant mycotoxins, present in feedstuffs commonly used in South African sheep feedlot diets.
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To evaluate the effect of mycotoxins on the production and profitability of sheep feedlot production systems.
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To evaluate the impact of two mycotoxin deactivators on the production and profitability of sheep feedlot production systems.