Selection indices for dairy cattle including fitness traits

In the present Swedish Total Merit Index (TMI) 13 subindices are weighted t ogether by means of their economic weights. This is correct under the assum ption that all genetic correlations between the subindices have zero-values . Recent research has revealed negative genetic correlations of the order o f -0.10 to -0.45 between the subindices for yield and those for daughter fe rtility and disease resistance. This is one of the reasons behind the prese nt revision of the Swedish TMI. Other reasons are new aspects of 'supertrai ts' or subindices as components in a TMI and new knowledge about the select ion for longevity. The selection index procedure is described and actual es timates on genetic correlations between key-traits in the two main dairy br eeds in Sweden are presented The proposed new TMI for Sweden is illustrated . The construction of it is a two step procedure. In the first step the sub indices are constructed. In the second step the TMI is calculated with cons ideration of the economic weights of the subindices and the genetic correla tions among them using the subindices as both variables and traits. In both steps the selection index principles of HAZEL (1943) are adopted.