Hair clippings, cayenne pepper and raw eggs — these are just a few of the odd ingredients  recommended to keep those pesky deer away from backyard gardens.

But what about farmers who have hundreds of acres of Christmas trees to protect? North Carolina State University Extension specialists have now found an effective, inexpensive alternative to available commercial products to keep the deer at bay.

The North Carolina State researchers, led by Jeff Owen, a Christmas-tree production specialist, are exploring the use of inexpensive, inedible food byproducts — such as dried blood and egg powder — typically sold in bulk to the pet-food industry to be used for flavoring. These byproducts cost 85 to 90 percent less than their commercial counterparts, and are found to be just as effective. Using these repellents — which can be purchased locally in bulk — may provide tree farmers an early Christmas present.

“These products have an unappealing taste, but the decaying smell actually elicits a fear response in the deer and keeps them away from the crops,” Owen says. “We’re continuing to look at similar products — like liver powder and fishmeal — to see if they work the same way.”

Owen says Christmas-tree farms in North Carolina have long dealt with deer which harm the trees by horning (thrashing market-sized trees with their antlers to mark territory) and browsing (eating the buds and shoots off  young trees.)