| Abstract: | Endotoxemia was characterized in neonatal calves given a small amount of colostrum and smooth Escherichia coli endotoxin by small-dosage (0.5 microgram/kg of body weight), slow (5-hour) IV infusion to mimic natural conditions. Responses were compared among 22 calves freely allotted to groups treated with saline solution (group I), preimmunization plasma (PP, group II), or antiserum to the rough mutant of E coli O111:B4 (J-5, group III) before endotoxin was infused. Bovine J-5 antiserum was produced by immunization of 4 cattle with J-5 boiled cell bacterin. The antiserum titers of immunoglobulin (Ig) M, IgG1, and IgG2 to the J-5 boiled cells, as determined by enzyme-linked immunosorbent assay, were 240, 7,680, and 960, respectively. The PP had enzyme-linked immunosorbent assay titers to J-5 of 240, 480, and 60 of IgM, IgG1, and IgG2, respectively. Endotoxemia in the 3 groups was characterized by significant (P less than 0.05) time-related changes in rectal temperature, heart rate, respiratory rate, capillary refill time, oral mucous membranes, nose moistness, scleral injection, attitude, PCV, total plasma protein concentration, WBC count and differential, plasma glucose, and lactate concentrations. The only significant treatment effects on clinical or laboratory values were higher mean total plasma protein concentrations in groups II and III 10 to 30 hours after endotoxin infusion was started than that in group I and increasing mean most-severe attitude abnormality score in groups I, III, and II (P less than 0.05). The administration of bovine J-5 antiserum to neonatal calves resulted in significantly higher serum IgG1 and IgG2 titers to J-5 boiled cells (P less than 0.05), and cross-reactive IgG2 to the challenge endotoxin (P less than 0.01) than did treatment with PP or saline solution; however, this antiserum did not mitigate the effects of sublethal endotoxemia. There was a significant negative correlation between IgG2 to J-5 at base line and the mean attitude abnormality score at 4.5 hours after infusion was started (P less than 0.05). |
