Acute Phase Response in Dairy Cows with Experimentally Induced Escherichia coli Mastitis

Abstract

Six Finnish Ayrshire cows were challenged intramammarily with 1500 CFU of Escherichia coli (E. coli) into single udder quarters, and the challenge was repeated into contralateral quarters 3 weeks later. All cows received flunixine meglumine once, and 3 of them were also treated with enrofloxacin. At the 2nd challenge, treatments were changed vice versa. The development of mastitis was followed by monitoring of systemic and local clinical signs, and with serial milk and serum samples. Intramarnmary challenge with E. coli produced clinical mastitis in all cows, the severity of the disease varying greatly between the animals. No significant changes between the 2 treatment regimens or sequent challenges were found for any of the clinical parameters. The response of each cow followed the same pattern after both challenges; three of the cows became mildly and the other 3 either moderately or severely affected. Two severely affected cows had to be euthanized because of severe mastitis.

Serum haptoglobin and amyloid-A concentrations peaked 2–3 days after bacterial challenge. Serum haptoglobin did not correlate with the severity of the disease. Serum amyloid-A rose gradually in the severely affected cows, and significant differences were found between severely versus moderately or mildly affected cows at day 4. Serum tumor necrosis factor alpha concentrations increased only in the severely affected cows. Serum Cortisol response was prolonged in the severely diseased animals, and was significantly lower after the second challenge. Serum nitrite/nitrate concentration increased in the severely affected cows. This indicated excess nitric oxide production during acute E. coli mastitis. Strongly decreased milk production, and high bacterial growth in the infected quarters were best predictors for the outcome from acute E coli mastitis.

Sammanfattning

För att åstadkomma experimentell mastit, inokulerades en juverfjärdedel hos sex finska ayrshire kor med 1500 CFU av E. coli. Tre veckor senare inokulerades kornas kontralaterala juverfjärdedel. Utvecklingen av mastit följdes upp genom att iakttaga allmänna och lokala kliniska symptom, och genom analys av serum och mjölkprover. Intramammär Inokulation med E. coli ledde till klinisk mastit hos alla kor, men svårighetsgraden varierade mycket mellan olika kor. Tre kor insjuknade milt, en måttligt och två allvarligt. De två allvarligt insjuknade korna måste avlivas p.g.a. grav mastit.

Serumkoncentrationerna av haptoglobin och amyloid-A nådde sina maximala nivåer 2–3 dagar efter Inokulationen. Serummängden av haptoglobin korrelerade inte med sjukdomens svårighetsgrad. Serumkoncentrationen av amyloid-A steg gradvis hos de allvarligt insjuknade korna, och ledde till signifikanta skillnader mellan grupperna på den fjärde dagen. Serumkoncentrationen av tumor nekros faktorn α steg endast hos de allvarligt sjuka korna. Kortisol-responsen i serum var förlängd hos de allvarligt sjuka korna och signifikant lägre efter den andra Inokulationen. Serumhalten av nitrit/nitrat steg hos kor med grav mastit; eventuellt ett tecken på ökad kväveoxidproduktion i samband med akut E. coli mastit. Å andra sidan är nitrit/nitrat halten i serum inte en pålitlig markör för ökad kväveoxid produktion. Kraftigt minskad mjölkproduktion och snabb bakterietillväxt i den infekterade juverfjärdedelen visade sig vara de viktigaste Symptomen som tyder på dålig prognos vid akut E. coli mastit.