Long-term selectionexperiments provide a valuable resource for understanding the genetic changesthat take place in animal improvement programs. The Virginia chicken lines havefor more than 50 years been subjected to single-trait, bi-directional, divergentselection for high and low juvenile body weight. It is one of the most wellstudied experimental populations in agricultural animals and has played an instrumentalrole in the understanding of the genetic basis of complex traits. In this paper,we summarize the findings from the more recent publications focusing on theefforts to identify the loci contributing to selection response as well as discussthe currently ongoing research. We conclude by describing some future researchprospects that promise to bring new, interesting insights into the biology ofcomplex traits in the near future and their implications for future animal improvementprograms.
