Preconditioning is a stressful period in which newly weaned steers are vaccinated, dewormed, commingled, and transitioned to a new environment and diets; these stressors compromise immunity, welfare, and growth. Chromium is known to improve glucose metabolism, reduce stress, and increase weight gain in cattle; however, the underlying physiological mechanisms during preconditioning are not fully understood. Thus, this experiment evaluated the effects of chromium propionate supplementation on rumen fermentation, immune response, temperament, and growth of Brangus steers during preconditioning. Steers received either no chromium or a daily dose of chromium propionate mixed with a small amount of soybean hulls, and bermudagrass hay was provided free choice. Steers supplemented with chromium exhibited a shift in rumen fermentation that indicated improved utilization of dietary fiber. Their glucose metabolism appeared more efficient, as evidenced by less circulating glucose and insulin levels, and their stress response was reduced, with less circulating cortisol and calmer behavior upon exiting the squeeze chute. Steers supplemented with chromium also mounted stronger responses to respiratory vaccines and gained more weight during the first 3 wk of preconditioning. Overall, chromium supplementation influenced the rumen fermentation, strengthened vaccine‑induced immunity, reduced stress, and supported better growth during preconditioning.

Read the full article in the Journal of Animal Science.