Rearing pre-weaned calves is one of the most challenging tasks on a dairy farm. Intensively reared calves are typically separated from dams within 24 hours of birth and fed restricted quantities of either whole milk or milk replacer until weaning. In contrast, a calf left with its dam will consume significantly more milk which leads to increased weight gain and improved health (Albright and Arave, 1997). Milk can be provided through ad libitum feeding systems with artificial teats allowing calves to consume more milk than with the traditional, bucket fed system. Milk replacer is a commonly used substitute feedstuff for whole milk on many calf rearing units in the UK. Milk replacers are formulated to meet the nutritional requirements of the pre-weaned calf but typically contain significantly less fat, on a DM basis, than whole milk. The aim of this trial was to investigate the effects of feeding whole milk versus a milk replacer to calves on a cold ad libitum basis on the milk and concentrate feed intakes and liveweights between the groups.