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 in creased once it was shown that the dietary supplementation of this biologic ally available form of Cr in humans resulted in the deposition of more musc le mass and improved glucose tolerance (since swine are produced as a prote in source for humans). Cr is biologically active in pigs via vena cava infu sion of a synthetic glucose tolerance factor-Cr. A variety of organic Cr so urces 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 demons trated biological responses in various trials, the magnitude and statistica l significance of the responses have varied. Since January 1996, when the U .S. Food and Drug Administration (USFDA) began to allow the marketing of Cr Pic 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 ti me. The situations in swine production that could potentially be most respo nsive to Cr supplementation are those associated with rapid growth, advanci ng age, reproduction, health-stressors (crowding, transport, disease challe nge, 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 eff iciency of growth, nitrogen absorption, nitrogen retention, and dry matter digestibility. Additionally, since pregnant swine vary considerably in thei r response to a glucose load and ability to control serum glucose levels, w ith 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 u p to 20% (or 2 pigs/litter) reported. Improved tissue sensitivity to insuli n 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 im pact observed thus far have been notable and assure that research with this mineral will continue. J. Trace Elem. Exp. Med. 12:149-161, 1999. (C) 1999 Wiley-Liss, Inc.