Effects of timing of vaccination relative to weaning and post-weaning frequency of energy supplementation on growth and immunity of beef calves.

A 2 × 2 factorial design study evaluated the impact of pre- vs. post-weaning vaccination and different post-weaning frequency of energy supplementation (daily vs. 3X weekly) on growth and immunity of beef calves. At 14 d before weaning (d -14), 48 Angus calves (24 steers and 24 heifers; 244 ± 33 kg; 196 ± 20 d) were stratified by BW and age, and randomly assigned to receive vaccinations against bovine viral diarrhea virus 1a (BVDV-1a) and parainfluenza-3 (PI-3) on d -14 and 0 (PRE) or 7 and 21 (POS), relative to weaning. Calves were weaned on d 0 and offered daily concentrate DM supplementation (50:50 soybean hulls and corn gluten feed; 71% TDN, 15% CP of DM) at 0.5% of BW for 7 d. On d 7, calves were stratified by vaccination scheme and assigned into 1 of 16 drylot pens (3 calves of same sex/pen; 4 pens/treatment). Pens were randomly assigned to receive similar weekly concentrate DM supplementation (1% of BW multiplied by 7 d) that was divided and offered daily (7X) or three times weekly (3X; Mondays, Wednesdays, and Fridays) from d 7 to 43. From d 0 to 43, calves were provided ad libitum ground tall fescue hay (57% TDN, 13% CP of DM). Blood samples were collected from jugular vein on d 0, 1, 3, 7, and 14, relative to the respective first vaccination, and on d 43 of the study. Effects of timing of vaccination × frequency of supplementation were not detected for any variable in this study (P ≥ 0.12), except for overall ADG from d -14 to 43 (P = 0.04), which was less for PRE-3X vs. PRE-7X, POS-3X, and POS-7X calves (0.60, 0.70, 0.70, and 0.77 ± 0.04 kg/d, respectively; P ≤ 0.08). Post-weaning total DMI and G:F did not differ among treatments (P ≥ 0.11). Pre-weaning vaccination increased plasma concentrations of cortisol and haptoglobin from d 0 to 3, relative to first vaccination (P ≤ 0.03), and decreased serum PI-3 titers on d 43 compared with post-weaning vaccination (P < 0.0001). Decreasing the supplementation frequency tended (P = 0.10) to increase overall plasma cortisol concentrations and reduce overall serum BVDV-1a titers. Hence, pre-weaning vaccination associated with reduced post-weaning frequency of energy supplementation caused the greatest reduction on calf growth performance. Post-weaning vaccination and daily energy supplementation alleviated inflammation and improved humoral immunity compared with pre-weaning vaccination and reduced post-weaning frequency of energy supplementation of recently weaned beef calves.