![]() rumen can 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 abortions, 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. and forages. This increases the risk of exposure to multiple mycotoxins. Forages (grazed and conserved), fermented feeds and by-products all represent a signifi cant risk to cattle, depending on soil contamination, forage harvesting date, silage management, purchased feed origins and on- farm feed storage conditions. It is important to note that mycotoxins seldom occur in isolation. It is not uncommon to fi nd multiple mycotoxins in the diet of dairy cows. This allows for interactions between them, which leads to synergistic or additive e ects. silages, straw) present the greatest threat to cattle. Even fresh grass for grazing can be contaminated with several mycotoxins. These typically include fungal endophytes that produce mycotoxins that protect the plant in some way, such as ergovaline and lolitrem B, as well as Fusarium mycotoxins, such as zearalenone or deoxynivalenol (DON). Zeralenone, DON, T-2, Fumonisin mycotoxins can be found throughout Ireland. To date, 248 Irish forage samples have been tested in the Alltech 37+® tested, 94 per cent contained mycotoxins, with an average of 4.62 mycotoxins present in each sample. producing Penicillium and Fusarium moulds. These will hamper natural bacterial activity in the rumen. The spread and multiplication of these throughout the pit is infl uenced by silage dry matter and the quality of preservation. Drier forages with a poor level of preservation will rapidly develop moulds. It is important to bear in mind that straw bedding can also be contaminated with mycotoxins. This can present a risk to dry cows that often consume large quantities of straw and forage. undiagnosed health issues in dairy cows, even when growing, harvesting and pit management is reasonably good. It is important to note that many of the symptoms associated with mycotoxicosis are non-specifi c, often meaning that a mycotoxin issue is `last in the queue' when diagnosing. The main e ect of many mycotoxins is impairment of the immune system. Immune-compromised animals will be at greater risk of pathology from other infectious and metabolic diseases, simply as a result of their `weakened' state. Other e ects include gastrointestinal examines the issue of mycotoxins |