State of the art milk production encourages an intensive system of maximising peak milk yield and minimising calving interval, epitomized by the 40 kg peak daily production and 10,000 kg 305 d lactation yield of a well bred, well fed Holstein. Given good management, milk yield typically declines at approximately 2% per week. It requires only a simple calculation to show, therefore, that this same cow would still be yielding around 20 kg of milk daily at 2 months before calving. The dilemma for the farmer is whether to dry her off or not, and if he is sensible he will probably do so. However, if he is really clever he will then change his rebreeding policy!