In many parts of Europe complementary forage crops such as maize silage, fodder beet and whole crop cereals have been widely used in dairy cow ration. In France, Germany and Holland, over 2.5 million hectares of maize are grown for silage, while in Denmark fodder beet and whole crop cereals are an integral part of most dairy cow rations. With the introduction of milk quota many farmers in the UK tried to maintain margin/litre by placing greater reliance on high quality home produced forage. On many grassland farms this strategy met with limited success as grass silage is often an unpredictable and variable commodity which is prone to low intakes. At the same time evidence was being accumulated in the UK as to the potential benefits of mixed forage diets in dairy cow ration. As a result the Milk Marketing Board of England and Wales established a programme work to determine the effect of incorporating a range of alternative forages or forage substitutes into grass silage based diets, on DM intake and milk production.