Physical and financial performance predictors for the dairy herd frequently take little or no account of current management practices, notably in respect of rebreeding. They do not anticipate the influence of unforeseen change or of increased beef bull use on the dairy herd in the longer term. The results of rebreeding management recording in 35 large dairy herds were reported at this meeting in 1983. These, and subsequent results, indicated that a decline in rebreeding management was most likely to influence annual milk sales and therefore income within no less than a 2 year period. The consequences of rebreeding management practices are long term and therefore it is essential to have the ability to look ahead to predict the likely outcome of change whether planned or unplanned. Rebreeding management influences calving pattern and any change influences feed requirements, both forage and other feeds. In addition, forage quality and quantity influence intake, the requirement for other feeds and therefore the financial performance. To take account of possible combinations of unplanned changes the computer program was developed as an extension to a program developed initially for the purpose of improving rebreeding and health management.