Heritabilities for regression and progression of rous sarcomas in the chicken

Variance components for hatch, line, and sire expressed as percentages of the total variance for each parameter of regression and progression of Rous sarcomas in chickens were obtained. Some parameters measured specific stages of regression or progression, and other parameters measured the entire process of regression or progression of Rous sarcomas. Heritabilities of each parameter were estimated. Additive genetic variation is strongly implicated in the defense of the chicken against early tumor growth and during the entire process of regression. Environmental variation is important in influencing the point in time of tumor growth when the first reduction in size of tumor occurs. There is evidence of genetic variation exclusive of the R-Rs-1 gene locus that assists the chicken to resist tumor growth. The coefficient of variation for each of the parameters is very large as compared with the coefficient of variation for economic traits such as body weight at broiler age.