The length and severity of negative energy balance postpartum is unfavourably correlated (genetically & phenotypically) with interval to first ovulation (de Vries & Veerkamp, 2000). During this period concentrations of free fatty acids (FFA), glucose, growth hormone (GH), insulin, insulin like growth factor 1 (IGF-1) and other hormones, all of which have links with many aspects of reproduction, are altered. A moderate heritability and genetic correlation between these parameters in the female and male (who is ultimately of most use for selection purposes) calf with female fertility could allow juvenile selection for fertility. With this in mind the objective of this study was to estimate the heritability of FFA, glucose, GH, insulin and IGF-1 concentration in male and female calves.