Abstract
This study of lymphocyte [ ]-mannosidase enzyme activities estimated gene frequency, fitness, and genotype means, variances, and transformations from 3,230 observations on Canadian Salers and Salers cross cattle with gender, birth year, percent Salers or other breeds, enzyme activity, and relationships to obligate carriers identified. The gene frequency estimate of 0.11 may have been influenced by sample ascertainment. Transformation parameters of .91 for heterozygotes and .86 for homozygotes (P < 0.05), evidenced skewness in the data. Fitness and breed type nested within genotypes were not significant (P > 0.05). Breed type, year of birth, and gender were significant (P < 0.05). Salers, Hereford, or Shorthorn breeding increased and Charolais or Simmental breeding reduced enzyme activity. Lymphocyte genotype means were closer together and variances were larger than those for plasma activity in a United States sample suggesting that the lymphocyte test has less power than the plasma enzyme test for discriminating among carrier and normal genotypes. However, when the data from the United States were reanalyzed ignoring concomitant information not available in the Canadian data (e.g., age, month of testing, and pregnancy status in females), the genotype means were closer and variances greater than for lymphocyte enzyme activity. This leads to the conclusion that the lymphocyte test is inherently more powerful than the plasma enzyme test for the discrimination of carriers of P-mannosidosis. The variance reduction due to averaging two repeated plasma enzyme activity tests did not significantly improve the power of the plasma test relative to the lymphocyte test in the absence of concomitant information. However, the plasma test utilizing this information is significantly more powerful than the current lymphocyte test for genotype discrimination, and the recommendation of this study is that Salers breeders should utilize the plasma enzyme activity test for genotype determination.
Collins, Julianne Shea (1994). Carrier genotype determination in Salers cattle using lymphocyte Beta-mannosidase activity. Master's thesis, Texas A&M University. Available electronically from
https : / /hdl .handle .net /1969 .1 /ETD -TAMU -1994 -THESIS -C712.