Moderately increasing Vitamin D fed to cattle prior to slaughter is a safe way of providing consumers with tender beef. That's the finding of studies conducted by scientists at the Agricultural Research Service's National Animal Disease Center (NADC) in Ames, Iowa, and Iowa State University.

The research was led by ARS physiologist Ronald Horst of NADC's Periparturient Diseases of Cattle Research Unit, and Donald Beitz, Iowa State professor of animal science and biochemistry.

It showed that raising cattle's blood calcium 20 to 30 percent by feeding the animals extra Vitamin D3, beginning two to three days before slaughter, results in an increase in muscle calcium and more tender cuts of meat.

Elevated calcium triggers the tenderizing process by activating postmortem muscle enzymes that can help degrade structural proteins that toughen meat. According to Horst, most mammals can tolerate blood calcium increases of up to 30 percent for three to five days without triggering ill effects in livestock or consumers.

Vitamin D3, the form of the vitamin found in humans and animals — though toxic if over-applied — helps people and animals build strong, healthy bones and teeth. A deficiency can cause bones to become thin, brittle, soft or misshapen and can lead to metabolic diseases such as milk fever in dairy cattle and osteoporosis in people.

The Vitamin D tenderizing method is being tested by private firms within the United States, with increased interest being shown during the past two years, according to Horst. ARS and Iowa State share a patent on this technique.

The scientists tested an identical method on pork. Although it led to improved meat color, no tenderizing effect was observed.

ARS is the chief scientific research agency of the U.S. Department of Agriculture.