Bovine plasma beta-mannosidase activity and its potential use for beta-mannosidosis carrier detection.

Plasma beta-mannosidase activities were determined for Salers cattle from 8 herds as an evaluation of this method for detection of beta-mannosidosis heterozygotes. Several biological factors, such as age, gender, herd, and risk of being a beta-mannosidosis carrier, were considered in this study. The mean enzyme activity for obligate heterozygotes (n = 8) was 55 U/ml (range = 43-65 U/ml), which was 59% of the mean enzyme activity for cattle that were low risk for being a carrier. These data indicate that bovine beta-mannosidosis is characterized by a gene dosage effect. The analytical and biological variation of plasma beta-mannosidase activity that was observed necessitates limiting the test to adult fullblood/purebred Salers cattle within a herd. Plasma beta-mannosidase analysis provides important information for intraherd selection of Salers cattle that are heterozygous for beta-mannosidosis.