Figure 1.
Figure 1.

Serum bovine viral diarrhea virus (BVDV) 1b neutralization antibody concentrations in calves exposed to steers persistently infected (PI) with BVDV for 72 h followed by an intratracheal challenge with 6 × 109 CFU of Mannheimia haemolytica (MH) serotype 1 on d 0 , occurring 12 and 84 h after the 72 h BVDV exposure for EarlyCh and LateCh, respectively compared with steers not exposed to calves PI with BVDV 1b and not challenged with MH (CON). There was a treatment × time interaction (P < 0.001; SEM = 8.60). Values plotted represent least squares means ± SE of the mean, calculated for 8 animals per experimental group. a–cWithin day, least squares means with different superscripts are different (P < 0.05).

 


Figure 2.
Figure 2.

Serum concentration of Mannheimia haemolytica (MH) whole cell (WC) antibodies (panel a) and MH leukotoxin (LKT) antibodies (panel b) in calves exposed to steers persistently infected (PI) with bovine viral diarrhea virus (BVDV) for 72 h followed by an intratracheal challenge with 6 × 109 CFU of MH serotype 1 on d 0 , occurring 12 and 84 h after the 72 h BVDV exposure for EarlyCh and LateCh, respectively compared with steers not exposed to calves PI with BVDV 1b and not challenged with MH (CON). There was a treatment × time interaction (P < 0.009, SEM = 0.293; panel A) for MH WC antibodies and a treatment × time interaction (P < 0.02, SEM = 0.135; panel B) for MH LKT antibodies. Values plotted represent least squares means ± SE of the mean, calculated for 8 animals per experimental group for both MH WC antibodies and MH LKT antibodies. a,bWithin day, least squares means with different superscripts are different (P < 0.05).

 


Figure 3.
Figure 3.

Rectal temperature of calves exposed to steers persistently infected (PI) with bovine viral diarrhea virus (BVDV) for 72 h followed by an intratracheal challenge on d 0 with 6 × 109 cfu of Mannheimia haemolytica (MH) serotype 1 at 12 and 84 h after the 72 h BVDV exposure for EarlyCh and LateCh, respectively, after BVDV exposure compared with steers not exposed to calves PI with BVDV 1b and not challenged with MH (CON). There was a treatment × time interaction (P < 0.001, SEM = 0.06). Values plotted represent least squares means ± SE of the mean, calculated for 8 animals per experimental group. a–cWithin a day, least squares means with different superscripts are different (P < 0.05).

 


Figure 4.
Figure 4.

Subjective clinical severity scores (CS) of calves exposed to steers persistently infected (PI) with bovine viral diarrhea virus (BVDV) for 72 h followed by an intratracheal challenge on d 0 with 6 × 109 cfu of Mannheimia haemolytica (MH) serotype 1 at 12 and 84 h after the 72 h BVDV exposure for EarlyCh and LateCh, respectively, after BVDV exposure compared with steers not exposed to calves PI with BVDV 1b and not challenged with MH (CON). There was a treatment × time interaction (P < 0.0001, SEM = 0.08). Values plotted represent least squares means ± SE of the mean, calculated for 8 animals per experimental group. a–cWithin a day, least squares means with different superscripts are different (P < 0.05).

 


Figure 5.
Figure 5.

Serum haptoglobin concentrations in calves exposed to steers persistently infected (PI) with bovine viral diarrhea virus (BVDV) for 72 h followed by an intratracheal challenge on d 0 with 6 × 109 cfu of Mannheimia haemolytica (MH) serotype 1, at 12 and 84 h fter the 72 h BVDV exposure for EarlyCh and LateCh, respectively, after BVDV exposure compared with steers not exposed to calves PI with BVDV 1b and not challenged with MH (CON). There was a treatment × time interaction (P < 0.001, SEM = 95.76). Values plotted represent least squares means ± SE of the mean, calculated for 8 animals per experimental group. a–cWithin a day, least squares means with different superscripts are different (P < 0.05).

 


Figure 6.
Figure 6.

Total white blood cell (panel a), neutrophil (panel b), and lymphocyte (panel c) counts in calves exposed to steers persistently infected (PI) with bovine viral diarrhea virus (BVDV) for 72 h followed by an intratracheal challenge on d 0 with 6 × 109 cfu of Mannheimia haemolytica (MH) serotype 1, at 12 and 84 h after the 72 h BVDV exposure for EarlyCh and LateCh, respectively, after BVDV exposure compared with steers not exposed to calves PI with BVDV 1b and not challenged with MH (CON). There were treatment × time interactions (P < 0.007, SEM = 0.66 [panel A]; P < 0.0001, SEM = 312.24 [panel B]; and P < 0.03; SEM = 350.54 [panel C]). Values plotted represent least squares means ± SE, calculated for 8 animals per experimental group. a,bWithin a day, least squares means with different superscripts are different (P < 0.05).