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

The effects of supplemental chromium (Cr) in the diet, or by direct ad dition to the culture medium on proliferation of bovine peripheral blo od lymphocytes (PBL) was evaluated with and without addition of the mi togen concanavalin A (con A). Twenty-four stressed steer calves were r andomized (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 arri val of calves from sales barns. Blastogenic activity was measured by u ptake of methyl-H-3-thymidine. The PBL from calves fed dietary Cr show ed increased (P < 0.05) blastogenic activity following incubation with culture medium containing the higher concentration (10 ug/ml con A) o f mitogen. An interaction between Cr and health status of calves occur red with or without mitogen (P < 0.05). Morbid animals had lower PBL b lastogenic responses but supplemental Cr increased (P < 0.05) this res ponse of morbid animals. However, supplemental Cr had no effect on res ponse 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 animal s fed the control diet from d 0 to 120, chelated Cr and CrCl3, were di rectly 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. Howev er, 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 certa in aspects of cell mediated immunity, which may contribute to the morb idity reduction of calves fed supplemental Cr.