Effects of Feeding Nutragen on Clinical Signs and Leukocytes in Calves Following Natural Exposure to Bovine Viral Diarrhea Virus and Subsequent Mannheimia Haemolytica Infection.

Two experiments (EXP1 and EXP2) evaluated the effects of NutraGen (NG) on calf health following exposure to bovine viral diarrhea virus (BVDV) on d -3 and Mannheimia haemolytica (Mh) infection on d 0. For each EXP, steers (BW = 251 ± 38.2 kg) were randomly allocated to 1 of 3 treatments (TRT). Treatments included a placebo (CON; EXP1 n = 5; EXP2 n = 5), a placebo fed from d -18 to d -3 followed by NG fed from d -3 to d 28 (CHLG; EXP1 n = 5; EXP2 n = 6), and NG fed from d -18 to d 28 (PREC; EXP1 n = 6; EXP2 n = 5). There was no treatment by time interaction (TRT×TME) or TRT effect for rectal temperatures (RT) or clinical scores (CS) in EXP1 or CS in EXP2 (P = 0.26). There was a TRT×TME for respiration rates (RR) during the first 24 h following Mh infection (P = 0.04), and a tendency for a TRT effect from d -3 to d 14, and overall in EXP1 (P ≥ 0.10). There was a tendency for a TRT×TME for RT from d -3 to d 14 in EXP2 (P = 0.04). There was a TRT effect for RR from d -3 to d 14 and overall in EXP2 (P ≥ 0.05). There was a TRT×TME for leukocytes during the first 24 h following Mh infection in EXP1 (P = 0.03) and overall in both EXP (P ≥ 0.001). There was no TRT×TME or TRT effect for neutrophils (NEU), lymphocytes (LYM), or NEU:LYM in EXP1 (P = 0.19); however, there were multiple TRT×TME and TRT effects for NEU, LYM, and NEU:LYM in EXP2 (P ≥ 0.05). These experiments suggest that NG has the potential to alter clinical and cellular responses during a bovine respiratory disease challenge. [ABSTRACT FROM AUTHOR]