Can moldy hay make a cow sick if so what should you do?

Moldy hay often won't make a cow sick due to the ability of the rumen to degrade the mycrotoxins found in such feed. You often won't see any issues in your animals, except lower feed intake because moldy hay doesn't taste nearly as good as good hay, however, certain molds can cause issues like aspergillosis or mycotic abortions, respiratory issues, and chronic issues (especially if fed for too long a period) like reduced feed intake, altered rumen fermentability, reduced fertility, reduced productivity, and higher morbidity (incidence of diseases, not death rates). It is much more concerning if you have a pregnant cow that you are feeding moldy hay to than to steers, bulls, replacement heifers or non-productive/dry, open cows. It is also very concerning if you feed such hay to horses, as it can cause serious problems such as colic or heaves.

If you have more "sensitive" animals such as pregnant cows, try to look for good hay instead and either save the moldy hay for those animals which will not be so sensitive to the mycotoxins. Sometimes a producer has no choice but to feed moldy hay to their animals, and often see few problems as a result. Still, it doesn't hurt to keep an eye on them to see if any issues--especially respiratory--come up. If there are issues that come up, contact a large-animal veterinarian and/or a bovine nutritionist to see what can be done to alleviate, prevent or treat the problems that do arise.

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