Submitted to: Journal of Animal Science
Publication Type: Abstract Only
Publication Acceptance Date: May 10, 1995
Publication Date: N/A
The objective of this research was to determine if calves primed with a low-level of infection with the protozoan parasite Sarcocystis cruzi, respond to a provocative EC differently than calves not infected. Sixteen 4-mo old Holstein bull calves were divided into control (C, noninfected, no EC), EC-control (no infection, +EC) and EC-infected (EC-I; 100,000 sporulated oocysts S. cruzi per os). A bolus EC (0.45 ug E. Coli 055:B5, iv) or saline was administered to each calf at a time after infection corresponding to the onset of acute phase response (APR, d 28-35). Plasma was analyzed for concentrations of TNF-alfa, glucose (GLU) and nitrite +nitrate (NOx, as an estimate of nitric oxide production). Liver samples were obtained at slaughter (+24h) and processed and probed for mRNA specific to inducible nitric oxide synthase (iNOS). EC-I displayed minimal signs of APR: Rectal temperature (RT) was elevated in 2/5 and feed intake decreased by 20% in 1 other calf. RT and plasma GLU, TNF-alfa and NOx remained constant throughout the sampling period in C. RT increased similarly in EC-I and EC-control; GLU responses were typically biphasic, the hyper- and hypoglycemic phases not different between EC-I and EC-control. NOx concentrations increased to 131 percent of the 0 h value at +2 h after EC in EC-I and remained significantly increased over those measured in EC-control through 12 h after EC. In contrast, NOx levels were not affected by EC. Analysis of mRNA suggested that the increase in NOx was not associated with iNOS. The data suggest that priming of calves with low-level parasitism modulates and may potentiate some responses to EC downstream from TNF.