Lymphocyte α-mannosidase — A supplementary test for determining mannosidosis genotype in cattle

Abstract

Extract

Mannosidosis is an inherited neurological disease of Angus calves associated with a deficiency of lysosomal α-mannosidase (Hocking et al., 1972). The disease can now be controlled through the ability to recognize heterozygous individuals that have less than half the normal levels of plasma α-mannosidase activity (Jolly et al., 1973; 1974a). As a consequence a test and control program, has been developed within the Angus bult-breeding herds of New Zealand, to be run by the Ministry of Agriculture and Fisheries in conjunction with the New Zealand Angus Association (Jolly et al., 1974b,c). Because various factors may influence plasma α-mannosidase activity, it is necessary to analyse results within relatively homogeneous age, sex and mob groups on the one property (Jolly et al., 1974a and unpublished data). In most groups there will be a small overlap area which, includes animals with high heterozygous and low normal values. Designation of the genotype of individuals in this area may be facilitated by reference to the genotype of parents when known, but there will remain a small percentage where a diagnosis cannot be made with an acceptable degree of probability. This applies especially where; groups are small, or when single animals are tested. For this reason the need for a supplementary test has been recognized (Jolly et al., 1974c). This paper presents an evaluation of the supplementary test currently used for animals whose plasma test was equivocal.