ARS | Publication request: Profile of the bovine acute-phase response following an intravenous bolus-dose lipopolysaccharide challenge

Submitted to: Journal of Innate Immunity
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 1, 2008
Publication Date: N/A

Interpretive Summary: A collaborative study was conducted involving scientists from the Livestock Issues Research Unit, the USDA-ARS SubTropical Agricultural Research Station in Brooksville, Florida, the University of Missouri, the University of Florida¿s Range Cattle Research and Education Center at Ona, and Texas Tech University to elucidate the bovine acute phase response following an intravenous challenge with an endotoxin. Specifically, the objective was to identify the changes that occur in immune and physiological parameters in beef cattle following an immunological challenge with an E. coli lipopolysaccharide (LPS). Our results demonstrated that the bacterial endotoxin induced a pronounced acute-phase response in beef steers. Tumor necrosis factor-alpha peaked rapidly after endotoxin challenge, followed by interferon-gamma, interleukin-1 beta, interleukin-6, and the acute phase protein, serum amyloid A. The data clearly demonstrated that cattle are sensitive to endotoxin and, therefore, high doses (greater than or equal to 2.0 microgram/kilogram of body weight) may not be required to elicit an experimentally useful response. Our results also indicate that body weight, body fat content, immune system maturity, and/or health history might be factors that result in variation among cattle given an LPS challenge. Bolus doses of LPS, using only pre-challenge values as controls for each animal, are convenient and consistent and should be useful in many experimental situations. The results of this research will be of particular interest to beef cattle feedlot managers, veterinarians managing the health of feedlot cattle, and scientists, whether from industry, academia, or industry, working in the area of beef cattle production, health, and well-being.

Technical Abstract: Two experiments were conducted to further define the acute-phase response to a lipopolysaccharide (LPS) challenge in beef steers. In Exp. 1, 9 crossbred beef steers (449 ± 12 kg BW) were used in a completely random design to determine the effects of 0.5, 1.0, or 2.0 micrograms of LPS/kilogram of body weight. Steers were catheterized in the jugular vein and then challenged the following day, and blood serum was collected and rectal temperature measured at 30-minute intervals from -1 to 6 hours relative to the LPS challenge. Cortisol and rectal temperature increased in response to the challenge, peaking and returning near baseline within 6 hours. Although the cortisol response was relatively mild for all doses, it increased linearly (P = 0.02) with LPS dose. Conversely, dose had no effect on rectal temperature (P > 0.50). In Exp. 2, 9 Angus steers (299 ± 5 kilograms body weight) were used in a randomized complete block design in environmentally controlled chambers to characterize the acute-phase response to 2.5 micrograms of LPS/kilogram of body weight. Steers were treated as described above, except that serum was collected from -2 to 8 hours relative to LPS challenge, and additional physiological and immunological assays were performed. Endotoxin increased (P < 0.05) serum concentrations of cortisol, tumor necrosis factor-alpha, interferon-gamma, IL-1 beta, IL-6, and serum amyloid A, as well as respiration rate, rectal temperature, and rump dermal temperature. Endotoxin decreased ear dermal temperature (P = 0.002), but it tended to increase (P < 0.10) ruminal temperature, shoulder dermal temperature, and shoulder perspiration rate. Concentrations of IL-4 and IL-2 or rump perspiration rate were not altered (P > 0.24) by the LPS challenge. To our knowledge, this report is the most complete characterization of the beef steer acute-phase response to endotoxin challenge in the published literature.