Mouldy Feeds for Beef and Dairy Cattle

Should dairy and beef producers be concerned about moldy feeds? The largest practical problem when feeding moldy feeds is the effect mold has on feeding value.  Energy levels will be up to 10-15% lower and palatability may be negatively affected.  This reduces performance if adjustments are not made.  Proper ration balancing is even more important when moldy feeds are being fed.  Cattle are more resistant to mycotoxins than monogastrics because most are detoxified in the rumen.  However, there are reports of mycotoxicoses in beef cows that were never attributed to a single mold but were most likely due to a combination of detected and possibly non detected molds. 
Pregnant cows and high producing cattle such as dairy cows are more susceptible to the effects of molds and/or mycotoxins than other classes of cattle.  Avoid feeding moldy feeds to t his group of animals, especially feeds containing Mucor and Aspergillus, which are known to cause mycotic abortions.  Mold analysis will identify the types of mold present and will help in targeting suspect feed to animals least at risk.  Blend down the moldy feed as much as possible in minimized potential problems.  There are no concrete recommendations for "safe" mold counts.  Recommendations for "high" mold counts range from 100,000 cfu/g to 1,000,000 cfu/g to 10,000,000 cfu/g.  Feeds with mold counts over 500,000 cfu/g should be diluted to prevent potential problems (eg. Feed refusal, low productivity).  A mold count of over 1 million cfu/g should definitely be considered high and dilution or avoidance of feeding should be done.  Animals on moldy feed need to be watched closely for decreased feed intake, lower productivity and / or health problems.
Nutrition Update
Volume 15 No.2, November 2004