The acute phase response as indicated by serum haptoglobin and total haemolytic complement activity (CH50) was measured in 72 cross-bred steer calves purchased at sales in Ontario. During the 28 day (d) trial, 18 steers were randomly assigned to each of the following groups: 1) control; 2) vaccinated (Infectious Bovine Rhinotracheitis, Parainfluenza-3, Bovine Viral Diarrhea, Bovine Respiratory Synctial Virus vaccine plus Pasteurella haemolytica vaccine); 3) supplemental chelated Cr (0.14 mg/kg); and 4) Cr plus vaccines. Haptoglobin concentrations were low at arrival, increased (P < 0.05) on day 7, and returned to near initial levels (P > 0.05) by day 14. Supplemental Cr reduced (P < 0.05) haptoglobin on day 7 when morbidity was highest. Following antibiotic treatment for respiratory disease haptoglobin was lower (P < 0.05) than during morbidity; however, during morbidity, haptoglobin concentrations were not greater in sick calves (P > 0.05) than in healthy calves. Complement activity was lowest on day 7 (P < 0.05) and peaked on day 14 (P < 0.05). Complement activity tended to be lower on day 7 for vaccine, Cr, and Cr+ vaccine groups; however, the difference from controls was not significant (P > 0.10). Complement activity did not increase on day 14 (P > 0.05) with Cr supplementation as in other treatments. Morbid calves had lower (P < 0.05) CH50 activity than healthy calves on day 14. Following antibiotic treatment, the Cr-supplemented group had higher (P < 0.05) CH50 than during morbidity. In general, chromium supplementation reduced the acute phase response in newly arrived feeder calves.

Performance, morbidity, serum Cortisol, plasma ascorbate (AsA) and serum tri-iodothyronine (T3) were evaluated in crossbred steer calves purchased at sales in Ontario. Thirty-three steers were randomly assigned to each of control; vaccination with Infectious Bovine Rhinotracheitis, Parainfluenza-3, Bovine Viral Diarrhea, and Bovine Respiratory Synctial Virus vaccine and P. haemolytica vaccine; 0.14 ppm supplemental chelated Cr; and Cr plus vaccines, for the 49 d trial. Supplemental Cr plus vaccine increased (P < 0.05) daily gain and feed intake during the first 28 d. Furthermore, vaccination increased (P < 0.05) 28 d gain for mid-performing steers. Vaccines, Cr and Cr plus vaccines did not reduce morbidity (P > 0.05); however, the Cr-supplemented group had fewer relapses (P < 0.05). Rectal temperature was reduced in both vaccinated and Cr-supplemented calves on days 10–16 post-arrival. Serum cortisol was reduced (P < 0.05) in vaccinated calves and morbid Cr-supplemented calves on day 28 post-arrival. The ratio of free to total T3 on day 7 and day 14 post-arrival, and AsA on day 14 post-arrival was greater (P < 0.05) for calves receiving supplemental Cr plus vaccines. Results confirm previous reports of the beneficial effect of Cr on performance, and indicate some additive effects of Cr and vaccines with respect to daily gain and plasma ascorbate. Key words: Chromium, vaccines, ascorbic acid, tri-iodothyronine, stress, calves