66. Impacts of Chromium Propionate Supplementation During Preconditioning on Growth, Temperament, Physiology, Immunity, and Rumen Fermentation of Brangus Steers

Abstract This experiment evaluated the effects of chromium (Cr) propionate supplementation during the preconditioning phase on growth, temperament, physiological responses, immune system, and rumen fermentation of Brangus steers. Sixty weaned male calves were stratified by body weight (BW; 255 ± 1.12 kg) and assigned to 12 bermudagrass pastures (0.5 ha each; 5 calves/pasture). Pastures were randomly assigned to one of two treatments (6 pastures/treatment): 1) Control (no Cr) or 2) Cr (KemTRACE Chromium 0.4%, Kemin Industries, Des Moines, IA). Calves received soybean hulls at 0.7% of BW, and Cr propionate was top-dressed at 0.01 mg Cr/kg BW per animal daily. On d 0, calves were vaccinated against infectious bovine rhinotracheitis (IBR), parainfluenza-3 (PI3) virus, bovine viral diarrhea virus types 1 and 2 (BVDV-1 and 2), bovine respiratory syncytial virus (BRSV), and Mannheimia haemolytica. Body weight, temperament traits, and blood samples were collected on d 0, 22, and 59 and liver biopsies and rumen fluid samples were collected on d 0 and 59. Quantitative and binomial variables were analyzed using the MIXED and GLIMMIX procedures of SAS, respectively. Calves supplemented with Cr tended to be heavier on d 22 (P = 0.10; 260 vs. 255 ± 1.12 kg) and had greater average daily gain from d 0 to 22 (P = 0.01; 0.46 vs. 0.25 ± 0.06 kg/day). Chromium supplementation reduced (P = 0.05) exit velocity on d 22, tended to decrease (P ≤ 0.10) serum insulin and glucose concentrations on d 22, and reduced (P = 0.04) the serum cortisol concentration on d 22. Calves supplemented with Cr had greater (P < 0.01) serum titers concentration for BVDV-1 and greater (P = 0.05) seroconversion rates for IBR and BRSV. Moreover, calves supplemented with Cr tended (P ≤ 0.10) to have greater concentrations of Cr in the liver and acetate and total volatile fatty acids in the rumen fluid. Additionally, calves supplemented with Cr had greater (P = 0.05) serum concentration of pentadecanoic acid on d 22 and 59, tended to have greater (P = 0.10) concentration of palmitic acid on d 59, tended to have lower (P = 0.09) concentration of stearic acid on d 22, and greater (P ≤ 0.01) concentration of eicosapentaenoic acid and osbond acid on d 59, and tended to have greater (P = 0.08) concentration of total saturated FA on d 59. In summary, supplementation with Cr propionate during preconditioning improved growth, enhanced immune responses to vaccination, reduced excitability, and modulated metabolic and ruminal fermentation profiles in beef calves.