ABSTRACT. This study was conducted to evaluate the changes in acute-phase proteins and cytokine concentrations in dairy cows with naturally occurring peracute Klebsiella pneumoniae (K. pneumoniae) mastitis and their association with the outcome of the disease. Seventeen Holstein cows with K. pneumoniae mastitis from 8 dairy farms were divided on the basis of outcome after local and systemic therapy into 2 groups comprising 8 euthanized cows and 9 that recovered. Changes in acute-phase proteins and cytokine concentrations in cows with K. pneumoniae mastitis were evaluated at the onset of the disease (day 0) and at days 3, 7 and 14 after therapy and compared with those of 13 healthy dairy cows. The concentrations of haptoglobin (Hp) and interleukin (IL)-6 in serum and α 1 -acid glycoprotein and IL-1β in serum and whey on day 0 were significantly (P<0.05) higher in the euthanized cows than in those that recovered and the healthy cows. A correlation (r=0.90, P<0.01, n=17) was found between IL-6 and Hp concentrations in sera from recovered and euthanized cows at day 0. This indicated that serum concentrations of Hp and IL-6 at the initial examination were prognostic factors for survival, and the cutoff values were 2,020 μg/ml and 32 ng/ml, respectively. These results suggest that IL-6 and Hp concentrations are involved in the manifestation of K. pneumoniae mastitis and may be possible indicators of the prognosis of peracute K. pneumoniae mastitis.KEY WORDS: acute-phase protein, cytokine, dairy cow, Klebsiella pneumoniae, peracute mastitis.

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