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The range of mycotoxins, can you identify them?
Mycotoxins seldom occur in isolation. It is not uncommon to find multiple mycotoxins in finished feed and this allows for interactions between them, which leads to synergistic or additive effects in the ruminant animal.
Did you know?
Mycotoxins in dairy cows can be a big issue. A healthy rumen has an ability to protect cattle against low levels of mycotoxins, but not all. Often these hidden thieves are likely to be responsible for numerous undiagnosed health issues.
In extreme cases they can cause abortion storms, severe scouring and sudden milk drop, but for the majority any mycotoxin presence is more likely to be seen as a subtle problem – perhaps the cows are not milking as well as they should be, or the dung is a little loose and variable, or cell counts have crept up and fertility is falling away.
Key mycotoxins: Penicillium
Ochratoxins are produced during storage of feedstuffs by different fungi and are found in both temperate and tropical regions. Ochratoxin A is the most prevalent. However, in a correctly functioning rumen this mycotoxin is rapidly degraded so is assumed to be a lesser threat to ruminants.
Clinical signs of Ochratoxin toxicity may include pulmonary oedema. Very high levels of Ochratoxin (e.g. 3ppm) can cause increased mortality.
Not considered to be a particularly potent mycotoxin, Patulin is produced by certain fungal species of Penicillium growing on fruit, including apples, pears and grapes. Fruit by-products stored under conditions that promote bruising and rotting increase the probability of Patulinformation. Contamination with Patulin has also been reported in vegetables, cereal grains and silage.
Clinical signs of Patulin toxicity in cattle include haemorrhaging in the digestive tract.
Key mycotoxins: Aspergillus
What is Aflatoxin? Aflatoxins can occur in all regions across the globe as a result of factors such as changing weather patterns and agricultural practices, but are of greatest concern in more tropical regions where the climate is generally warm and humid. Be cautious though if feed is being imported from tropical regions.
Key mycotoxins: Fusarium
Tricothecenes [e.g. T-2 toxin, deoxynivalenol (DON or Vomitoxin)] are common field toxins found in grains and silages. These mycotoxins can be partially metabolised in the rumen, although their breakdown can be inhibited by acidic rumen conditions. Susceptibility to Tricothecenes vary between species, breeds and management systems. For example, beef cattle and sheep a more tolerant to DON consumption than dairy cattle.
Clinical signs of Tricothecene toxicity include reduced feed intake, lower weight gains and lost milk production, diarrhoea, reproductive failure and even mortality.
Zearalenone often occurs in combination with DON in naturally contaminated cereals or forages. This mycotoxin mimics the activity of hormones (as an oestrogen analogue), which causes the majority of the reproductive-related symptoms seen, especially in pregnant animals. Zearalenone is partially metabolised in the rumen to alpha-zearalenol and, to a lesser extent, to beta-zearalenol. These breakdown compounds have shown no toxic effects on rumen bacteria, but alpha-zearalenol is about four times more oestrogenic than its parent mycotoxin and so this rumen-mediated transformation actually causes greater toxicity. The rate of zearalenonetransfer into milk is low and is currently through to present no real risk to consumers of dairy products.
Clinical signs of zearalenone toxicity include abortions, decreased embryo survival, infertility, vaginitis, feminisation of young males and mammary gland enlargement in virgin heifers.
Fumonisins occur worldwide in feedstuffs. In contrast to other mycotoxins, Fumonisin B1 (the most prevalent of the Fumonisins) is relatively slowly and poorly metabolised in the rumen. Ruminant target organs damaged by these mycotoxins include the liver and kidney.
Clinical signs of Fumonisin toxicity include reduced feed intake, lower weight gain and lost milk production.