|Burton, Jeanne - VISITING SCIENTIST|
|Dubeski, Paula - AGRI. CANADA RES. STN.|
|Mallard, B - UNIV. OF GUELPH, CANADA|
Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 27, 1996
Publication Date: N/A
Interpretive Summary: Our previous studies have shown that health and the function of the immune system of feedlot calves and dairy cows are improved when organic chromium is added to their diets. The present study was performed in dairy cows to determine if chromium affects the production of substances called cytokines by white blood cells. These substances influence the function of the immune system. Blood cells were collected from chromium-supplemented and unsupplemented cows around the time of calving. The cells were then cultured for 24, 48, and 72 hours with a compound, called a mitogen, that causes the cells to produce cytokines and begin to proliferate. Chromium decreased the production of three cytokines, interleukin-2, interferon-gamma, and tumor necrosis factor-alpha, especially by cells collected from cows 4 to 6 weeks after calving. This was the same time period that supplemental chromium was shown by our group to increase white blood cell proliferation in response to the mitogen. These results suggest that chromium can affect the cells of the cow's immune system by influencing their production of cytokines.
Technical Abstract: The objective of this study was to determine whether supplementing the diets of dairy cows during the peripartum period with organic trivalent chromium (Cr) influenced the capacity of their peripheral blood mononuclear cells to produce acute phase cytokines in response to mitogenic stimulation in vitro. Nine cows were fed .5 ppm Cr per head per day from 2 wk prepartum to 6 wk postpartum, and 10 other periparturient cows served as unsupplemented controls. Mononuclear leukocytes, enriched from peripheral blood on weeks 0,1,4, and 6 of lactation, were cultured with or without the T-lymphocyte mitogen, concanavalin A. Culture supernatants harvested at 24, 48, or 72 h were assayed for interleukin-2 interferon-gamma, and tumor necrosis factor-alpha. The cytokines were barely detectable in supernatants from unstimulated cultures, while supernatants from mitogen- stimulated cultures contained higher concentrations of each cytokine. Concentrations of interleukin-2 and tumor necrosis factor-alpha were highest in 48 h supernatants, while interferon-gamma was highest in 72 h supernatants. Cows fed Cr had significant decreases in concentrations of all three cytokines in culture supernatants of the mitogen-stimulated mononuclear cells, particularly around peak lactation for the 24 and 48 h cultures. These results extended those from our previous studies that organic Cr was immunomodulatory in metabolically-stressed cattle, and may help explain the enhanced resistance to infectious diseases observed in those studies.