Comparison of Methods for Assay of Fecal Proteolytic Activity

Fecal proteolytic activity (FPA) in ten normal dogs was readily detected either colorimetrically using azocasein substrate or by radial enzyme diffusion into agar gels containing casein substrate. Daily FPA ranged from 17 to 207 azocasein units/g (ACU/g) or 4 to 18 mm of casein hydrolysis, while mean 3‐day FPA ranged from 58 to 101 ACU/g or 7 to 15 mm. Studies of proteolytic activity remaining after treatment of fecal extracts with a specific trypsin inhibitor indicated that trypsin accounted for 0% to 71% of proteolytic activity. Proteolytic activity decreased steadily in fecal specimens stored at room temperature or above, but there was only slight loss in activity during storage for up to 5 days at 4d̀C. Proteolytic activity was unaffected by repeated freezing and thawing and samples could be stored for long periods at ‐20d̀C without noticeable loss of activity. It is concluded that assays of FPA using either azoprotein substrate or radial enzyme diffusion into agar gels containing casein substrate allow evaluation of exocrine pancreatic function in dogs, provided that several samples are tested. These methods are suitable for application in a variety of species.