Plasma diamine oxidase activity decline with diarrhea severity in calves indicating systemic dysfunction related to intestinal mucosal damage.

The aim of the present study was to investigate whether abnormalities in plasma diamine oxidase (DAO) activity reflect the degree of intestinal mucosal disorder in calves with diarrhea. A total of 50 Holstein calves were enrolled. Thirty-six of the 50 calves presented diarrhea and were sub-classified by severity based on fecal status (0: firm, 1: pasty, 2: loose, and 3: watery) and blood pH (acidemia: blood pH <7.25) as follows: Seventeen calves exhibiting watery diarrhea and/or fall into acidemia were sub-categorized into the severe group. The other nineteen calves exhibiting pasty or loose diarrhea and not fall into acidemia were sub-categorized into the moderate group. The remaining 14 calves without diarrhea were assigned to the control group. The plasma DAO activity was significantly lower (p < .01) in the calves with severe or moderate diarrhea than in the control group. In addition, the plasma DAO activity was significantly lower (p < .05) in the severe group than in the moderate group. The relationship between plasma DAO activity and fecal score (r = -0.55, p < .01) in calves with diarrhea were found to have significantly and negatively correlated by Spearman's rank test in this study. Our results suggested that plasma DAO activity reflect the degree of intestinal mucosal disorder due to diarrhea.