Leucocytic changes in cows given intravenous injections of Escherichia coli endotoxin.

Single intravenous injections of Escherichia coli endotoxin into normal cows produced dose dependent leucocytic and febrile responses. Injections of 5 to 20 microgram endotoxin induced a neutrophilia between 4 and 8 h, whereas 50 to 500 microgram produced a severe neutropenia for 4 to 6 h followed by a gradual increase in neutrophils along with slight to moderate left shift. Higher doses caused progressively severe lymphopenia and greater increase in fever than the lower doses. It was concluded that blood leucocytic changes during the early part of endotoxin-induced mastitis are partly related to systemic absorption of endotoxin, and that the size of the bone marrow neutrophil reserve in the cow could be estimated by injecting 5 to 10 microgram of endotoxin intravenously.