Expert: Jim Hyland - 3/5/2010

Question
My horses have chewed on a few pine trees in their pasture. I have placed plastic on the trees but on some they have reached the sap. Is there anything I can do to save these trees?

Answer
You did not say the size of the pines so i will give you both answers
Small trees--if you are talking about the horses eating the terminal bud of the young pine this can kill the trees.  These small trees need to protected from this damage.

Larger pines--i expect this is what you are referring to. Horses seem to have the habit of eating the bark from trees. Thus is a major problem with hardwood trees but pines with the capacity to exude sap will heal over the wound. Unless the bark is removed from all the way around the trunk the pines will recover. I would use chicken wire instead of plastic to wrap the trunk beyond the reach of the horses. Also could paint the trunks with old motor oil or another smelly type liquid and this will deter the horses from the bark.  

Why do they do this.


During the late winter and early spring months, horses may be seen eating the bark of trees. This may be due to a nutrient deficiency, possibly of one of the minerals. If you have been providing a mineral block, check to see if it has been consumed and needs to be replaced. If not, you might try providing one to see if it provides the missing nutrients.

Wood chewing can also occur during this time due to the low fiber content of the cool season grasses that are available to them. Therefore, by eating the tree bark, they may be making up for some of the lack of bulk or fiber. It has been reported in controlled research that horses increase wood chewing during wet and cold weather. The wetness softens the wood and the coldness increases the maintenance energy requirements to maintain normal body temperature.

Fiber digestion is essentially a fermentation that produces heat which can be used to maintain body temperature or warmth. Therefore, the increased fiber intake from wood may actually increase fermentation and heat production in the horse to maintain normal body temperature. If the horse is in need of bulk or fiber, try providing a good quality hay.

However, in most cases, it seems that the horse likes the taste of bark. A lot of trees produce sap that the horse may find sweet. In this case, you might try putting something on the tree that is harmless to the horse but that he will find the taste of unpleasant.