Genetic parameters for feed intake and feed efficiency in growing dairy heifers.

Feed intake and feed efficiency are of importance in cattle breeding programmes. A divergent selection experiment on feed intake was carried out during three generations. Young performance-tested bulls were selected on high or low dry matter roughage intake. The effective phenotypic selection differential in sires was 3.12 units of phenotypic standard deviation. Dams in first generation were randomly chosen. Data of progenies of 38 selected bulls were recorded in growing, pregnant and lactating heifers for feed intake, daily gain and milk yield. This study is confined to the analysis of genetic parameters of 417 growing heifers. Data were analyzed in an animal model. Roughage intake had a heritability of 0.56. Adjustment of roughage intake for differences in metabolic body weight changed the heritability to 0.19. Feed efficiency was calculated as gross feed efficiency and as residual feed intake (RFI). RFI is feed intake-adjusted for maintenance and daily gain and reflects differences between animals in efficiency of using energy. The heritability estimate was 0.18 for gross feed efficiency and 0.22 for RFI. It is concluded that measuring feed intake in addition to body weight could be important for reducing residual feed intake in growing heifers