chewing on trees

Question
I have 3 horses that are stalled at night (in winter) and out every given chance, weather permitting. They have grass to graze, I ride them about 3 times a week. I tie them to trees off and on through out the week (which they dont chew on). But when out grazing they have just started to chew on the trees. One cribs already, but the other two do not. I have heard they chew because they are bored, but they are doing exactly what they have been doing for the last 3 years. Why start now?

Answer
Dear Melanie,

Sorry for the delayed response.  No one really knows what horses chew on trees.  Some speculate that it is the sugar in the sap in the spring others that it is a mineral need that they are missing.  To my knowledge I have not seen any real research on this.  I would look at their diet and make sure that their mineral needs are met by feeding a mineral supplement that balances their main source of forage.  I'm afraid that beyond that I do not have much advice to offer.

Best regards,

Clair Thunes, PhD
Independent Equine Nutritionist,
Equilibrate Equine Consulting,
www.equilibrateequine.com
clair@equilibrateequine.com