Submitted to: American Dairy Science Association Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: June 20, 1999
Publication Date: N/A
Quantitative trait loci (QTL) affecting milk yield, health, type, and canonically transformed traits were studied for seven large US Holstein grandsire families using the granddaughter design. Families were genotyped for 31 microsatellite markers, and marker effects were analyzed for 28 traits (21 type traits, 5 milk traits, somatic cell score (SCS), and productive life) and 16 canonical traits derived from type and production traits. Permutation tests were used to calculate experiment-wise error rates. A critical value of P = 0.1 was used to determine significance. Nine putative QTL were identified within specific families for the traits on the original scale. Six of these markers affected type traits and had estimated allele differences of 1.24, 0.79, 0.64, 1.02, 1.34, and 0.50 genetic standard deviations (GSD) for body depth, dairy form, feet & legs composite index, feet & legs score, strength, and udder composite index on chromosomes (BTA) 4, 27, 3, 2, 4, and 10, respectively. Two markers affected protein percentage and had estimated allelic effects of 0.056 and 0.050 percent in two families on BTA 6 and 7. The same marker on BTA 7 was associated with differences in SCS in a different family with an estimated allelic difference of 0.13 units of SCS. Three markers were associated with differences in the canonically transformed traits. Markers on BTA 6, 5, and 9 had estimated allelic differences of 0.94, 1.69, and 0.24 units for two canonical conformation traits and one canonical production trait, respectively. These 31 microsatellite markers supplement the completed original 70 markers. Additional markers are being added to allow interval analysis where putative QTL have been identified and to increase marker density.