Genotype and Variability in Dairy Lactation Records

In quantitative genetics, the variation of individuals within genetic groups is commonly attributed to environment. The assumption is then made that the environmental variances are similar from one group to another. Complications arise in the application of selection index theory when this assumption is not made. The results reported here indicate that in a population of dairy records, the environmental variance is not similar from one genetic group to another. Johnson (1945) and Wadell, Van Vleck and Henderson (1960) found similar results with fewer data