A review on the effects of mycotoxins in dairy ruminants

Mycotoxins are toxic chemical compounds of low molecular weight produced by moulds. Throughout the years, the resistance of ruminants to mycotoxins has been assumed to be an almost absolute fact and the negative effects of these metabolites have been largely neglected by dairy farmers. However, such resistance should not be taken for granted as ruminants are fed various feed materials which might contain several different mycotoxins and in some cases, grazing animals might consume other mycotoxins via pasture. Metabolisation of mycotoxins in the rumen is not equivalent to complete detoxification. Moreover, its potential degradation is highly dependent on rumen microflora stability and pH, which vary according to feed composition and to the direct antimicrobial activity of mycotoxins. Young animals, high-yielding cows and animals in the transition period should be given particular attention as they are more susceptible to the negative effects of these toxic metabolites. A brief overview on the occurrence of these toxic compounds in commodities commonly used in dairy feeds will set the scene for a review of their impacts on rumen function and rumen health, reproduction, feed intake and performance, carry-over into milk, liver toxicity and foot health/lameness and other metabolic disorders.