Supplementation with chromium propionate can increase milk production in dairy cows, numerous studies have shown. So, what exactly is the mode of action?

Jerry Spears, dairy scientist at North Carolina State University, explained this recently at the Cornell Nutrition Conference in East Syracuse, N.Y.

"Chromium functions by potentiating the action of insulin," he said.

Chromium has the ability to improve insulin sensitivity, which helps promote glucose uptake in the cells of adipose and muscle tissue. Insulin stimulates a specific glucose transporter known as GLUT-4. Improved insulin sensitivity and glucose uptake results in less mobilized fat and more efficient use of energy. Numerous studies have shown that higher milk production and increased feed intake occur among chromium-supplemented cows.

"The greater feed intake of chromium-supplemented cows in early lactation may relate to adipose tissue being more sensitive to insulin," Spears said.

Limited research has indicated that chromium supplementation may also improve reproductive performance, he said. During the summer of 2009, the U.S. Food and Drug Administration issued a regulatory discretion letter which permitted the use of chromium propionate as a source of chromium in cattle diets. It was the first such approval for a trace mineral in cattle diets since 1979.