CHARACTERIZATION OF GENOTYPE BY ENVIRONMENT INTERACTION IN DAIRY CATTLE IN DIFFERENT REGIONS OF THE UNITED STATES

The major goal of this project is to identify possible differences in the genetic makeup of individuals in different regions in the United States. Our objective is to characterize the differences in sires ranking in New England and California. We will use milk yield, and fat, and protein content as the phenotypes of interest.We also aim to compare the genetics underlying lactation curves in the two regions. Finally, we will investigate if there are different regions associated with the phenotypes in each region. The project is divided in two main objectives, one for each year. Objective 1) To study the genetic correlation and the sire ranking for milk yield, protein production/percentage, and fat production/percentage in California and New England. We will compare the records for each region as a separated trait, and we will evaluate the interaction between the genetics and the environment. We intend to evaluate how much different the sire selection would be if the evaluation was by region instead of unified across the whole Country. We will also comparethe lactation curve parameters in each geographical region and the genetics underlying it. We will fit a complex statistical model to evaluate the shape of the lactation curves and how much of the differences are because of the genetics. The first part of this objective was done under the Multistate project in the first year. Objective 2) We will use the results of Objective 1to study genomic regions associated with all phenotypes studied (milk, fat, and protein production and lactation curve parameters). This step is essential for the understanding of how the genome and the environment affect the phenotypes.