Mycotoxin Management: Sources and Effects on the Animal
Mycotoxins are responsible for numerous undiagnosed health issues in UK dairy and beef cattle, even when growing and harvesting conditions are reasonable. For the majority the result of mycotoxin presence is likely to be seen as a subtle problem; the symptoms will be many and varied, but the outcome in all cases will be reduced performance and lost profits.
This several parts blog will help identify risk areas on farm and enable you to take action which can be implemented rapidly to better manage an existing mycotoxin challenge and reduce the chance of further contamination.
Mycotoxins are low molecular weight, secondary metabolites produced by moulds that have been stressed by environmental and management factors, such as extremes of temperature, drought, flooding and harvesting technique. They are toxic to animals in low concentrations and exhibit strong physico-chemical resistance. One mould is capable of producing several mycotoxins and one mycotoxin may be produced by several different moulds.
There are three main mould groups of concern: Fusarium, Aspergillus and Penicillium.
Fusarium moulds are of field origin i.e. they proliferate on the crop while it is still in the field. Storage moulds, such as Aspergillus and Penicillium develop, as the name suggests, during storage of the crop or grain. This includes storage during ensilage. While Aspergillus is less of an issue in the northern parts of Europe, levels of its associated mycotoxin, Aflatoxin, are regulated under EU law. In terms of negative effects on farm, the Fusarium and Penicillium mycotoxins are by far the most problematic in the UK and NI. As mycotoxins are very stable compounds that ‘survive’ on the crop/grain long after the initial mould has disappeared, the absence of mould does not necessarily mean the crop is ‘clean’ (the reverse situation also applies) and, although routine testing is carried out for mycotoxins, such as DON, producers utilising home-grown grain and conserved forage to feed animals on farm may be at increased risk of introducing a mycotoxin challenge to their animals.
Mycotoxins compromise animal health and performance. It’s important to note that many of the symptoms associated with mycotoxicosis are non-specific often meaning that a mycotoxin issue is ‘last in the queue’ when diagnosing. The main effect of many mycotoxins is impairment of the immune system. Animals that are immune-compromised will be a greater risk of pathology from other infectious and metabolic diseases simply as a result of their ‘weakened’ state. Other effects include gastrointestinal disturbances, feed intake depression and reproductive abnormalities. ZEA is often responsible for the latter. Cystic ovaries, irregular cycles and embryonic abnormalities all fall under the remit of ZEA. Probably one of the most important but underestimated effects is the antibiotic action of Penicillium mycotoxins. Patulin, PR toxin and Roquefortine C are all produced by Penicillium moulds and have the same action in the rumen as Penicillin does in the human body – antibiotic. It is true that ruminants are less susceptible to many mycotoxins compared with non-ruminants due to the ability of the rumen microbes to degrade them to less harmful compounds. However, if this ability becomes impaired by an antibiotic action, then the animal becomes increasingly susceptible to those mycotoxins. To this end, Penicillium mycotoxins are receiving increased attention.
Penicillium mycotoxins are described as ‘silage’ mycotoxins due to their presence in conserved forage (including silage, haylage and hay) and there are many factors that contribute to the level of contamination. As Penicillium is a storage mould, ‘stressors’ during harvesting and ensiling lead to proliferation of associated mycotoxins. Contamination avoidance is virtually impossible but following good silage management practices can go a long way to minimising the risk to livestock. Again, the variability in, and timing of, this year’s weather has done little to help the situation. One of the key points is the recognition and understanding of the mycotoxin problem. Part of this is recognition of the fact that the majority of exposure is to chronic, low concentrations of multiple mycotoxins and, as such, any interventions, including use of a mycotoxin binder, must be able to deal with a wide suite of mycotoxins at any one time. As mentioned previously, mycotoxins are often the last in the diagnostic queue and traditional analyses used for their detection often lacked sufficient sensitivity. Current analytical progress has seen the development of a highly sensitive and rapid system for detecting not only the presence but the level (down to ppq in some cases) of over 37 individual mycotoxins. This technology is validated and supersedes the traditional techniques for determining levels of contamination in various materials, including grains and forages.
In conclusion, mycotoxin contamination is unavoidable, however, negative effects can be minimised through knowledge and understanding of the threat they pose.