Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/14/2009
Publication Date: 8/14/2009
Citation: Carroll, J.A., Arthington, J.D., Chase Jr., C.C. 2009. Early weaning alters the acute phase response to an endotoxin challenge in beef calves. Journal of Animal Science. 87:4167-4172. 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, and the University of Florida’s Range Cattle Research and Education Center at Ona, to elucidate the bovine acute phase response following an intravenous challenge with an endotoxin in early weaned and normal weaned beef calves. Specifically, the objective of the current study was to determine if the innate immune response of early weaned calves (weaned at 80 days of age) differed from normal weaned calves (weaned at 250 days of age) in response to an i.v. endotoxin challenge. For this study, we used 18 Brahman x Angus calves (8 and 10 early and normal weaned, respectively). Early-weaned calves were maintained on ryegrass pastures (January to May) and limpograss pastures from May to the start of the study in August. Calves were provided supplement (80:20 blend of soybean hulls and cottonseed meal) daily at 1.0% of body weight. Normal weaned calves were weaned from their dams at 45 days prior to the start of the study and maintained on limpograss pastures as a group along with the early weaned calves. One week prior to the endotoxin challenge and serial blood collection, all calves were housed in their respective individual study pens (4 x 6 m) for acclimation. Results of the current study clearly reveal that the age of calf weaning significantly influences the release of pro-inflammatory cytokines (TNF-alpha, IL-1 beta and IL-6) into the blood following i.v. endotoxin challenge. Based upon these data, the innate immune system of early weaned calves appears to be less naive than that of normal weaned calves. Additionally, the differential IFN-gamma responses indicate that the immune system of early weaned calves may be more effective at recognizing and eliminating endotoxin. Collectively, these data suggest that an altered innate immune system may be responsible for the improved feedlot performance and reduced stress associated with transport previously reported in early weaned calves. This research will be of particular interest to cow/calf producers, feedlot owners, and other scientists in industry, academia, or government agencies working in the area of beef cattle production and/or animal health and well-being.
Technical Abstract: Previous research indicates that early weaning prior to shipment can reduce transportation-induced increases in acute phase proteins (APP), and can increase subsequent performance in the feedlot. These data suggest that the combination of weaning and transport stress may compromise the immune system of calves, thus hindering subsequent performance and health. Therefore, our objective was to determine if the innate immune response of early weaned calves (EW; 80 d of age) differed from normal weaned calves (NW; 250 d of age) in response to an endotoxin challenge. Eighteen Brahman x Angus calves (8 and 10 EW and NW, respectively; 233 ± 5 kg BW) were used. Prior to the study, calves were maintained on pasture with supplement. All calves were acclimated to their study pens for 1 wk prior to a lipopolysaccharide (LPS) challenge. One d prior to LPS challenge, calves were fitted with an indwelling jugular catheter. Blood samples were collected at 30-minute intervals from -2 to 8 hours. At 0 hour, all calves received an i.v. infusion of LPS (1.0 micrograms/kg body weight). Serum samples were stored at -80 degrees Celsius until analyzed for cortisol (CS), tumor necrosis factor-alpha (TNF), interleukin-1 beta (IL-1), IL-6, interferon-gamma (IFN), ceruloplasmin (Cp) and haptoglobin (Hp). While LPS increased serum CS (P less than or equal to 0.001) no weaning age effect (P greater than or equal to 0.15) was observed. A weaning age x time interaction (P less than or equal to 0.04) was observed for TNF, IL-1, IL-6 and Cp such that concentrations of these indices were greater in the NW compared to EW calves. For Hp, a weaning age effect (P less than or equal to 0.03) was observed with NW calves having greater average Hp concentrations compared to EW calves. Interestingly, the weaning age x time interaction (P less than or equal to 0.001) for IFN revealed greater IFN in EW opposed to NW calves. Based upon these data, the innate immune system of EW calves appears to be less naïve than that of NW calves. Additionally, the differential IFN response indicates that the immune system of EW calves may be more effective at recognizing and eliminating endotoxin. These data suggest that an altered innate immune system may be one of the factors responsible for the improved feedlot performance previously reported in EW calves.