Automatic calf feeding systems are used to reduce the labour requirement of calf rearing. They can also be used to increase milk intake. Major points to consider when mechanizing calf rearing are first, control of voluntary milk intake and second, ensuring that each individual obtains sufficient. Level of feeding depends on the system selected. The greater milk intake the less solid food will be consumed and the latter can fall to a level where ingesta entering the rumen is insufficient to stimulate its development. Thus calves fed milk at high levels experience a check at weaning but once solid food is eaten rumen development is rapid so this effect is not usually prolonged. Ad libitum feeding initially gives faster growth but the post-weaning check reduces this effect. However, overall the outcome can be expected to be advantageous. For calves being reared as heifer replacements or for beef it is more economical to restrict milk powder intake and to early wean the calves. A major requirement of a mechanized calf rearing system for these purposes is therefore to restrict milk intake per calf but not run the risk of some calves not receiving sufficient. For veal calves the requirement is to ensure maximum milk intake per calf. Figure 1 schematically represents a range of possible calf rearing systems.