Assessment of Physiological Parameters in Response to an Endotoxin Challenge in Crossbred Steer Progeny Sired By Brahman Bulls That Experienced Prenatal Transportation Stress

The objective of this experiment was to assess physiological responses to an endotoxin challenge in crossbred male progeny whose Brahman sires experienced prenatal transportation stress (PS) in utero. Sixteen steers (PNS group) sired by 3 PS bulls (gestating dams were transported for 2 h at 60, 80, 100, 120, and 140 ± 5 d of gestation) and 16 steers sired by 3 control bulls were evaluated. Fifty-six d after weaning, pen score (PS; 1=calm and 5=excitable), exit velocity (EV; m/sec) and temperament score [TS; (PS+EV)/2] were recorded. Four d later (d -6), steers were transported from Raymond, MS to Lubbock, TX (1,200 km). On d -2, steers were fitted with rectal temperature (RT) probes and jugular cannulas, and placed in individual stanchions. On d 0, all steers received an endotoxin challenge (LPS; 0.25 μg/kg BW). Physiologic variables included RT, sickness behavior score (SBS; 1=lowest and 5=greatest sickness behavior), and complete blood count (CBC). Endocrine and metabolic variables included cortisol, glucose, and insulin. Serum cortisol, glucose, and SBS were assessed at 30-min intervals, RT at 1-h intervals, and CBC at 2-h intervals from -2 to 8 h and at 24 h relative to LPS administration (0 h = administration). Serum insulin was assessed at 30-min intervals from -2 to 6 h. All data were analyzed with a fixed model specific for repeated measures, and TS was a covariate for cortisol, insulin, and glucose. There was a pre-LPS cortisol treatment by time (P<0.01) interaction, with greater cortisol in controls than PNS steers at time 0. There was no influence (P>0.1) of treatment or time on pre-LPS glucose or insulin. Controls had greater (P<0.01) post-LPS cortisol, which changed (P<0.01) over time. There was a post-LPS treatment by time interaction for glucose and insulin (P<0.05). There was a post-LPS SBS treatment by time interaction (P=0.02), with a greater SBS in PNS steers from 0.5 to 3 h. The RT changed (P<0.01) over time in response to LPS but was not affected by treatment (P>0.1). All CBC variables changed over time in response to LPS (P<0.01). The PNS steers had lower hemoglobin and hematocrit counts, but greater platelet, white blood cell counts, and monocyte counts than controls (P<0.01). The PNS steers had lower (P<0.01) eosinophil counts than controls from 4 to 8 h after LPS. Male progeny from prenatally stressed bulls had altered hematologic, endocrine, and metabolic responses to an endotoxin challenge.