Tolleson, Mallory Williams (2016-05). Genome-Wide Association for Udder Composition Traits in Bos indicus - Bos taurus Cows. Master's Thesis.
The objective of this study was to conduct a genome-wide association study for udder traits for crossbred cows. Average teat diameter, average teat length, and udder support score were evaluated in cows (n = 295) from 13 full-sib embryo transfer Nellore-Angus F2 families and 4 half-sib natural service families sired by the same bulls in central Texas. Cows were analyzed together as paternal half sibs. Effects included in the analyses were cow age nested within birth year-season combinations. Cow was included as a random effect. Repeated measures analyses were conducted to generate residuals for each cow then averaged per cow for each trait and used as individual phenotype. Association analyses for teat diameter and length on each quarter, the average of the four quarters, and udder support score were conducted.
A total of 15 associated (-log10[FDR] >= 1.3) markers were detected. Udder support had 15 significant SNP detected, exclusively within a 26.4 Mb region on BTA 5 (21.6 to 48.1 Mb), while average teat diameter had one associated marker, also located on BTA 5. No SNP associations were detected for average teat length or any individual teat traits. These results identified associated markers within genes that have an involvement in the development and regulation of the mammary system and suggest that BTA 5 is significant for udder traits in beef cattle.