Mycotoxins are often talked about but until their impact starts to be seen on milk production they tend to be overlooked on most dairy units. Dr Nicola Walker explains the scale of the challenge.
Despite growing evidence highlighting the damage mycotoxins in feed and forage can cause, the threat is still often overlooked.
Dr Nicola Walker, AB Vista’s ruminant product development manager, says: “Up to 90 per cent of maize silages, two-thirds of wholecrop cereal silages and more than 70 per cent of total mixed rations [TMR] can be contaminated with mycotoxins, mainly from fusarium moulds growing on crops pre-harvest.”
The figures come from an industry survey of silage samples carried out in 2014-15. The results highlight just how susceptible maize silage is to high levels of mycotoxin contamination.
Although lower dry matter grass silages are much less prone to secondary fermentation within the body of the clamp, they are highly susceptible to the growth of moulds such as aspergillus at the top surface.
These so-called ‘storage’ moulds can also affect clamped moist feeds as well as dry feeds, which are allowed to get damp, either from rain, yard run-off or during transport.
This is a particular problem for feeds sourced from regions of the world where humidity levels can be high.
It is the cereal crops – including maize – and cereal-based feeds which represent the greatest threat, with fusarium-produced mycotoxins deoxynivalenol, zearalenone and T2 toxin particularly damaging to ruminants.
Important mycotoxins generated by aspergillus moulds include aflatoxin B1, which is a carcinogen which can accumulate in muscle tissue (meat) and cause aflatoxin M1 in milk, with potentially serious implications for human health.