PROLIFERATION OF PERIPHERAL-BLOOD LYMPHOCYTES OF FEEDER CALVES IN RESPONSE TO CHROMIUM

The effects of supplemental chromium (Cr) in the diet, or by direct addition to the culture medium on proliferation of bovine peripheral blood lymphocytes (PBL) was evaluated with and without addition of the mitogen concanavalin A (con A). Twenty-four stressed steer calves were randomized (three animals per pen) to the following treatments: control diet (high quality corn silage) and control diet supplemented with 0.14 ppm chelated Cr. The PBL blastogenic activity was accessed using 0, 2 and 10 ug/ml con A on d 0, 7, 14, 21, 28, 35, and 49 following arrival of calves from sales barns. Blastogenic activity was measured by uptake of methyl-H-3-thymidine. The PBL from calves fed dietary Cr showed increased (P < 0.05) blastogenic activity following incubation with culture medium containing the higher concentration (10 ug/ml con A) of mitogen. An interaction between Cr and health status of calves occurred with or without mitogen (P < 0.05). Morbid animals had lower PBL blastogenic responses but supplemental Cr increased (P < 0.05) this response of morbid animals. However, supplemental Cr had no effect on response of healthy animals. When soluble chelated Cr was directly added to the culture medium at 0, .045, .45 and 4.5 ppm, Cr enhanced (P < 0.05) blastogenic activity at both concentrations of mitogen, as well as without mitogen stimulation. In addition, using PBL from eight animals fed the control diet from d 0 to 120, chelated Cr and CrCl3, were directly added in the PBL culture medium at 0, 0.0045, 0.045, 0.45 and 4.5 ppm, and the same enhanced blastogenic activity was observed. However, chelated Cr showed greater (P < 0.10) enhancement of PBL activity at 0.045 to 0.45 ppm and CrCl3 at 0.0045 ppm concentration (P < 0.05). These results confirmed previous indications that Cr can effect certain aspects of cell mediated immunity, which may contribute to the morbidity reduction of calves fed supplemental Cr.