Deer hunters have long touted the virtues of their venison as a lean and healthful meat.

But the good-for-you applecart was upset this past winter when fragments of lead bullets were discovered in ground venison donated to North Dakota food shelves.

That surprise discovery prompted Minnesota officials to test venison donated to Minnesota food programs. Testing of some 12,000 samples revealed that 22 percent of them had varying amounts of lead fragments.

Since lead is a toxic material that can cause neurological damage and other health issues, particularly in children, all 12,000 pounds of donated ground venison was thrown away.

The suspected source of the lead contamination was, not surprisingly, the bullets hunters use to bag their deer. Depending on the design and construction of the bullet, they can be prone to disintegrate upon striking an animal.

To determine which types of bullets are more likely to cause lead contamination, the Minnesota Department of Natural Resources recently completed research on the performance of various bullet types by firing a variety of ammunition into deer and sheep carcasses.

Tests concluded last week with a final session of shooting at the Carlos Avery Wildlife Management Area near Forest Lake.

Marrett Grund, a research biologist with the Department of Natural Resource’s Farmland Wildlife Research Unit near Madelia, said the research was conducted to replicate as closely as possible, the way hunters would handle their deer.

“We would handle the carcasses just like a hunter would, including evisceration, after bagging a deer in the field,” he said. “To our knowledge, no other agency has done this kind of research.”

The carcasses were then taken to the University of Minnesota’s School of Veterinary Science where necropsies were performed and x-rays taken of the carcasses to determine the nature and extent of bullet fragmentation.

All total, 70 different types of bullets were used on 9 deer carcasses taken from the TB Management Zone in northwest Minnesota, and 40 carcasses of sheep, which closely replicate a deer’s body structure.

While the latest test results conducted last week with muzzleloader bullets, shotgun slugs, and solid copper bullets were not yet available, results from earlier tests of bullets fired from high-powered rifles were. There were no surprises.

“We found nothing shocking,” Grund said. As expected, lighter bullets designed to fragment and severely deform to impart more stopping power resulted in more fragments in and around the wound channel.

Bullets with heavier and jacketed construction, the kind typically used on bigger animals such as elk fragmented far less or not at all.

Grund said the testing was meant to educate hunters about the risks lead fragments pose and how to minimize that risk, perhaps through the use of bullets of different types or materials.