Serum Concentrations of Haptoglobin and Haptoglobin-Matrix Metalloproteinase 9 (Hp-MMP 9) Complexes of Bovine Calves in a Bacterial Respiratory Challenge Model

Abstract

<p>Serum haptoglobin (Hp) and haptoglobin matrix metalloproteinase 9 complexes (Hp-MMP 9) have been identified as biomarkers with diagnostic potential in cattle with conditions resulting in an acute inflammatory response. The purpose of this study was to evaluate potential diagnostic applications of serum Hp and Hp-MMP 9 concentrations in calves with BRD and establish a timeline for their detection in calves experimentally challenged with <em>Bibersteinia trehalosi</em> and <em>Mannheimia haemolytica.</em> Thirty-five cross bred dairy calves were inoculated via tracheal catheterization with either a PCR confirmed leukotoxin negative <em>B. trehalosi</em> isolate, a PCR confirmed leukotoxin positive <em>B. trehalosi</em> isolate, a <em>Mannheimia haemolytica</em>isolate, a combination of leukotoxin negative <em>B. trehalosi</em> and <em>M. haemolytica</em>, or a negative control. Serum samples were collected throughout the study. Calves were euthanized and necropsy performed on day 10 post inoculation. <em>M. haemolytica</em> inoculated calves had increased lung involvement. Serum Hp and Hp- MMP 9 concentrations were elevated compared to the other treatment groups. Increases in serum Hp and Hp-MMP 9 concentrations for the <em>M. haemolytica</em>group were significantly different from other study groups on day 7 of the study. <em>B. trehalosi</em> inoculated calves did not have increased lung involvement compared to control calves, but the leukotoxin positive <em>B. trehalosi</em> group demonstrated increased serum Hp-MMP 9 concentrations from day 3 to the end of the study compared to the pre-inoculation concentrations. Serum Hp-MMP 9 concentration is a useful diagnostic tool for detecting early pulmonary inflammation in calves challenged with <em>B. trehalosi</em> and <em>M. haemolytica</em>. Serum Hp-MMP 9 may also be a useful tool in detecting subclinical pulmonary inflammation in challenged calves.</p>