Chromium and swine nutrition

Swine are used as a model for humans in many biomedical research projects. Interest in the use of chromium as chromium picolinate (CrPic) for swine increased once it was shown that the dietary supplementation of this biologically available form of Cr in humans resulted in the deposition of more muscle mass and improved glucose tolerance (since swine are produced as a protein source for humans). Cr is biologically active in pigs via vena cava infusion of a synthetic glucose tolerance factor-Cr. A variety of organic Cr sources exist, but the two that have seen the greatest amount of research are organic Cr from yeast and from CrPic. Although these two forms have demonstrated biological responses in various trials, the magnitude and statistical significance of the responses have varied. Since January 1996, when the U.S. Food and Drug Administration (USFDA) began to allow the marketing of CrPic as a source of Cr at a level of up to 200 ppb in the complete diet, the swine industry has been able to use an organic form of Cr for the first time. The situations in swine production that could potentially be most responsive to Cr supplementation are those associated with rapid growth, advancing age, reproduction, health-stressors (crowding, transport, disease challenge, etc.), and dietary inadequacies. Improvements in carcass composition (i.e., more lean, less fat) were the first reported effects of supplemental organic chromium. In some studies, feeding CrPic increased the rate and efficiency of growth, nitrogen absorption, nitrogen retention, and dry matter digestibility. Additionally, since pregnant swine vary considerably in their response to a glucose load and ability to control serum glucose levels, with consequent effects on reproduction, the potential of Cr supplementation to improve reproductive performance has been of interest. Positive effects have been observed in conception rate and litter size, with increases of up to 20% (or 2 pigs/litter) reported. Improved tissue sensitivity to insulin has been reported in both growing and reproducing pigs with several forms of organic chromium; alterations in other hormones in reproducing females also have been reported. The biological responses and potential economic impact observed thus far have been notable and assure that research with this mineral will continue.