Immunomodulatory effects of chromium (III) in ruminants: A review of potential health benefits and effects on production and milk quality

The immunomodulatory potential of dietary chromium (Cr) has been demonstrat ed in cattle. Specific Cr-attributed health and production benefits, in bot h beef and dairy cattle, are postulated to arise in part from the direct an d/or indirect consequences of this immunomodulatory potential and from the long-recognized effects of Cr on insulin and glucose metabolism. Recent stu dies in dairy heifers evaluated. (1) peripheral tissue responsiveness to in sulin following feed supplementation with varying concentrations of Cr-yeas t, and (2) blood lymphocyte (BL) insulin receptor expression and binding af finity following dietary supplementation with Cr-chelate. These findings su ggest that Cr potentiation of insulin action may be mediated primarily by p ostreceptor pathways. In addition, in vitro studies examined the effect of Cr-supplemented culture medium on the quantitative expression of several cy tokine mRNAs in concanavalin A (ConA)-stimulated bovine BLs. These findings support a previously reported Cr-mediated decrease in interleukin-2 (IL-2) activity in the culture medium of ConA-stimulated BLs from Cr-supplemented cows. They further suggest a role for immunoregulatory cytokines, particul arly IL-2, as a mechanism through which Cr exerts its effects upon the bovi ne immune response. Additionally, the differential inhibition of bacterial growth rates by Cr in vitro, simulating possible effects upon anaerobic rum en bacteria populations, suggests a potential indirect mechanism by which d ietary Cr may influence ruminant health and performance. The next generatio n of studies elucidating the cellular and molecular mechanism of Cr immunom odulatory effects will benefit greatly from a reliable, chemically defined source of Cr bioplexes and from the experience with Cr in ruminants. J. Tra ce Elem. Exp. Med. 12:131-140, 1999. (C) 1999 Wiley-Liss, Inc.