Q: We have a potential client for our wood shaving and they wanted to know what species might be toxic to horses. Can you help?

A: Black walnut is known to be very toxic to horses. Chips containing as little as 5 percent walnut are hazardous.

The Ohio State Extension Service also lists all oaks (because of their high tannin content), but they are a problem only if the horse were to chew and digest the wood. Contact your local county extension office for up-to-date advice.