Effects of bacterial lipopolysaccharide injection on white blood cell counts hematological parameters and serum glucose insulin and cortisol concentrations in ewes fed low- or high-protein diets

摘要

Bacterial lipopolysaccharide endotoxins (LPS) elicit inflammatory responses reflective of acute bacterial infection. We determine if feeding ewes high (15.5 %) or low (8.5 %) CP diets for 10 d altered inflammatory responses to an i.v. bolus of 0 (control), 0.75 (>L75), or 1.50 (>L150) μg LPS/kg BW in a 2 × 3 factorial (n = 5/treatment). Rectal temperatures, heart and respiratory rates, blood leukocyte concentrations, and serum cortisol, insulin, and glucose concentrations were measured for 24 h after an LPS bolus (bolus = 0 h). In general, rectal temperatures were greater (P ≤ 0.05) in control ewes fed high CP, but LPS increased (P ≤ 0.05) rectal temperature in a dose-dependent manner at most times between 2 and 24 h after bolus. Peak rectal temperature in L75 and L150 occurred 4 h after bolus. A monophasic, dose-independent rise (P ≤ 0.023) in serum cortisol occurred from 0.5 to 24 h after bolus, with peak cortisol at 4 h. Serum insulin was increased (P ≤ 0.016) by LPS in a dose-dependent manner from 4 to 24 h after bolus. Insulin did not differ between control ewes fed high and low CP diets but was greater (P < 0.001) in L75 ewes fed low compared with high CP and in L150 ewes fed high compared with low CP. Elevated insulin was not preceded by elevated serum glucose. Total white blood cell concentrations were not affected (P ≥ 0.135) by LPS, but neutrophil and monocyte fractions of white blood cells were increased (P ≤ 0.047) by LPS at 12 and 24 h and at 24 h after bolus, respectively, and lymphocyte fraction was increased (P = 0.037) at 2 h and decreased (P ≤ 0.006) at 12 and 24 h after bolus. Red blood cell and hemoglobin concentrations and hematocrit (%) were elevated (P ≤ 0.022) by LPS at 2 and 4 h after bolus. Rectal temperatures and serum glucose were greater (P ≤ 0.033) in ewes fed a high CP diet before LPS injection, but these effects were lost at and within 2.5 h of bolus, respectively. Feeding high CP diets for 10 d did not reduce inflammation in ewes during the first 24 h after LPS exposure but may benefit livestock by preventing acute insulin resistance when endotoxin exposure is mild.