Effects of pregnancy on the fever response of sheep to a Gram-negative pyrogen.

摘要

Ewes commonly display a reduction of immunity to gastrointestinal parasites during the periparturient period, so it is possible that other components of immunity change at this time. To determine whether the reported absence of fever in full-term-pregnant ewes occurs in a breed farmed commercially in New Zealand, 12 pregnant and 9 non-pregnant Coopworth ewes were treated with injections of Escherichia coli lipopolysaccharide (LPS) at five-weekly intervals for 3.5 months. An initial dose-response study, conducted in a separate group of ewes, determined that a dose of 200 ng/kg LPS induced fever (?.7鳦 increase in rectal temperature) in our sheep. Rectal temperature and plasma glucose concentration were monitored at the time of LPS injection and 4h later. The magnitudes of both the mean increase in rectal temperature (range 0.4 to 2.1鳦) and the mean reduction of plasma glucose concentration (range 2.9 to 17.7 mg/dl) appeared to vary throughout the study but they were not affected by pregnancy, nor was there any difference in these parameters between the two groups of sheep at the periparturient period. However, there was a reduction in the incidence of fever generated by LPS in the post-lambing period, lactating ewes appearing to have smaller increases in rectal temperature (mean increase 0.4鳦, n=11) than their non-lactating counterparts (mean increase 0.8鳦, n=8). We conclude that at least part of the immune response to LPS (i.e., fever and the reduction of plasma glucose concentration) is maintained in our Coopworth ewes at full-term of pregnancy.