CHARACTERISTICS OF THE FEBRILE RESPONSE IN PEKIN DUCKS

We measured body temperature in Pekin ducks for 22 h after intravenous injection of the lipopolysaccharide (LPS) of gram negative bacteria a t doses of 0, 1, 10, and 100 mu g . kg body mass(-1). The ducks develo ped monophasic fevers showing increases in peak temperature reached an d duration of fever with increases in dose of LPS. Body temperatures o f unrestrained telemetered ducks without access to food and water were similar to those of saline-injected controls in the fever experiments , but were lower in the morning than when the same birds had access to food and water. This nocturnal hypothermia may have resulted from ene rgy restriction imposed by lack of food and water. The dose of LPS req uired to elicit a fever of over 18 h duration (100 mu g . kg(-1)) will elicit a biphasic fever of 5 h duration in rats. Pekin ducks did not exhibit biphasic fever even at the highest LPS dose administered, indi cating that while fever is superficially similar in the two homeotherm ic classes, there may be differences in details of the mechanism. The similarities of the dose/response characteristics to that of mammals l ends support to the theory that fever in vertebrates has a common phyl etic origin.