This thesis investigates the effects of increasing fat at the expense of lactose in milk replacer (MR) on growth, voluntary feed intake, feeding behaviour, and blood metabolites in Holstein calves. When investigating the effects high fat MR fed ad libitum, it was found that higher fat inclusion reduced voluntary MR intake without an evident effect on solid feed intake or growth. However, greater fat inclusion reduced hunger-related behaviours during the weaning period. When investigating the effects of high fat MR on growth, solid feed intake and blood metabolites in feed restricted calves, no alterations on growth or solid feed intake were observed. Nevertheless, changes in blood metabolites were detected. Calves consuming the high fat diet having higher blood NEFA and glucose concentrations than calves consuming a traditional MR. The findings of these studies suggest that increasing fat inclusion at the expense of lactose boasts promising results for enhanced feeding programs such as the reduction of hunger-like behaviours around weaning, and the comparable growth performance.